advertisement
Models1492 and 2092
SERVICE MANUAL
2 YEAR LIMITED WARRANTY
This product is warranted by CERONIX to be free of defects in material and workmanship for a period of two years from the date of purchase.
In case of a fault, developed during this time, it is the customer's responsibility to transport the defective unit to CERONIX or one of the authorized service centers for repair.
Please attach a note describing the problem.
All parts and labor are free of charge during the warranty period.
CERONIX
12265 Locksley Lane
Auburn, CA. 95602-2055
(530) 888-1044
This warranty does not cover mechanical breakage due to physical abuse.
CERONIX shall not be liable for any consequential damages, including without limitation damages resulting from loss of use.
Some states do not allow limitation of incidental or consequential damages, so the limitation or exclusion may not apply to you.
This warranty gives you specific rights and you may also have other rights which vary from state to state.
®
®
Recognized under the Component Program of Underwriters Laboratories Inc. and the Canadian Standards Association.
CERONIX
All rights reserved.
The information contained in this manual is subject to change without prior notice.
ABOUT THIS MANUAL
This manual is specifically written to aid the service technician, repairing
CERONIX Models 1492 and 2092 color monitors.
There are three main sections:
1. General Description.
2. Circuit Description.
3. Solutions to Problems.
INTRO-
DUCTION
Block
Diagram
Description
BLOCK
Diagram
Schematic Circuit
Description
Problem
Solving
Tools &
Examples
Appendix
A
Video
Interface programs
To understand how the Monitor works, it is best to know what each circuit does and how each circuit relates to the other circuits.
The Block Diagram is presented in a simplified view and a comprehensive view to accomplish the goal of understanding the whole unit.
Once the general picture is clear, the complexity of each circuit will be easier to understand.
The Circuit Description is also written in two views, a simplified view and a detailed view to help give the reader a clear understanding of what each component does. This understanding is most helpful for the more complex problems or multiple problems that sometimes occur.
The Trouble Finder section is made up of an index, which lists symptoms of problems, and a list of possible solutions. Part of this section also deals with setting up conditions which make it easier to trouble shoot specific circuits such as the power supply.
1
TABLE OF CONTENTS
About This Manual. 1
CERONIX Models 1492 and 2092 Electrical Specification. 3 & 4
Drive Signals to the Monitor Input voltage and waveforms, work sheet. 5
1492 and 2092 Simplified Block Diagram. 6
Video Section Description. - - - - - - Blocks A-D 7
Auto Bias and Socket Board. - - - - - Blocks E-G 8
Blanking, Sync, & Vertical.
- - - - - - Blocks H-L 9
Horizontal Deflection & Remote. - - Blocks M-Q 10
Horizontal Size & Power Supply.
Power Supply Continued.
- - -
- - - - - - - -
Blocks R-U 11
Blocks V-Y 12
1492 and 2092 Monitor BLOCK DIAGRAM. 13
1492 and 2092 Monitor SCHEMATIC 14 & 15
Video Interface Circuit Description. 16 & 17
Video Interface Schematic. 18
Video Amplifier Circuit, Function, Description. 19
Video Amplifier Circuit Description. 19 & 20
Socket Board, Degaussing Circuit, and Legend Description. 21
Blanking and Master Gain Circuit, Function, Description. 22
Blanking and Master Gain Circuit Description. 23
Blanking and Master Gain Schematic. 24
Block
Diagram
Description
Video
Socket Board
Blanking
Master Gain
Circuit &
Function
Description
Replacement PARTS LIST. 25 & 28
1492 and 2092 Main Board ASSEMBLY DRAWING. 29 & 30
Block Diagram Review. 31
Auto Bias and Auto Bright Circuit, Function, Description. 32
Auto Bias and Auto Bright Circuit Description. 33
Auto Bias and Auto Bright Schematic. 34
Vertical and Horizontal Sync Circuit Description. 35
Vertical Deflection Circuit, Function, Description. 36
Vertical Deflection Circuit Description. 37 & 38
Horizontal Deflection Circuit Description. 39 & 40
Horizontal Raster Width Control Circuit Description. 41
Horizontal Raster Width and Position Control Schematic. 42
Simplified Power Supply Circuit, Function, Description. 43
Simplified Power Supply Circuit Description. 44
Switch Mode Power Supply Circuit Description. 45
Switch Mode Power Supply Schematic. 46
Equipment setup for repairing the Model 1492 Monitor. 47
Problem Solving Tools. 48
Appendix A --- Setup and Convergence Procedure. 49
Appendix B --- Video Interface Programs. 50 to 55
Appendix C --- Resistor Array Layout for; B, C, G, H, I, & J. 57 & 58
Auto Bias
Auto Bright
Sync
Vertical
Horizontal
Power Supply
Circuit &
Function
Description
2
CERONIX
MODELS 1492 and 2092 Electrical Specification
1.
INPUTS
Standard Video Configurations, available, are:
A. Positive Analog
Video
Source
D-A
301
Ω
Video
Gnd
.6mA
301
Ω
To Amp.
Monitor
Source only
{
Black level
Saturated color
Source and
Monitor
{
Black level
Saturated color
1492 & 2092
Min.
Typ.
Max
0V 0V
.05V
3.1V
3.2V
3.3V
.06V
.09V
.15V
1.61V
1.69V
1.75V
B. Negative Analog
Video
Source
D-A
Video
Gnd
To Amp.
905
Ω
V
Blk.+.7
V
R
IN
Monitor
Red & Green Black level
Blue Black level
Saturated color
5.4V
5.6V
5.8V
4.85V
5.05V
5.25V
.7V
.9V
1.1V
C. 4 Line TTL
Video
Source
*
R,G,B
Video
Intensity
To Amp.
BIAS
+12V
VB
Black level
Color on
Low intensity
0V
.2V
.5V
2.7V
3.5V
6.0V
0V .2V
.4V
Gnd
Monitor
Full intensity
4.5V
4.6V
4.8V
*
No pullup resistor on intensity line.
Note: RS170 and other voltage combinations optional for analog video.
2.
The Sync signals may be of either polarity and separate or composite.
Sync
Source
Hs
Vs
1.8K
1.8K
.15V
High input voltage
Low input voltage
2.2V
3.5V
20V
-2.7V
.30V
.80V
Gnd
220
Ω
,
2 PL
Monitor
Horizontal sync pulse
Vertical sync pulse
1.5uS
4.5uS
31uS
120uS .5mS
1.5mS
For composite sync, vertical and horizontal sync lines are connected together.
Horizontal frequency
15.3KHz 15.6KHz 15.9KHz
Vertical frequency
60Hz 65Hz
45Hz 50Hz
3.
The Power to the monitor is to be supplied by a secondary winding of an isolation transformer.
115VAC 50Hz or 60Hz
230VAC 50HZ or 60Hz
Power
Model 1492 Model 2092
Min.
Typ.
Max.
Min.
Typ.
Max.
85VAC 115VAC 145VAC 90VAC 115VAC 145VAC
170VAC 230VAC 290VAC 180VAC 230VAC 290VAC
32W 44W 60W 30W 50W 67W
3
4. The remote Controls are located on a separate PCB for easy access.
H SIZE--------------Horizontal raster size
V SIZE---------------Vertical raster size
V RAS. POS.-----Vertical raster position
H POS-------Horizontal picture position*
M GAIN---------------------Master gain
Model 1492
Min.
Max.
9.9"
6.3"
0"
11.4"
10.3"
.44"
.9" Right 2" Left
Dark
Screen
Light
Screen
Model 2092
Min.
14.8"
10.0"
0"
Max.
16.3"
14.0"
.60"
1.2 right 2.8" left
Dark
Screen
Light
Screen
The board Controls are located on the main PCB, and are:
Focus on the flyback transformer and an optional Horizontal hold control.
* For start of horizontal sync 1.7uS after end of picture.
5.
Picture
Video response is measured at the tube socket, using low capacitance coupling. The input signal should be fully damped and faster than the expected response.
Rise time
Fall time
Overshoot
Band width
Horizontal blank time
Vertical blank time
Horizontal linearity
Vertical linearity
Pincushion
Model 1492 Model 2092
Min.
Typ Max.
Min.
Typ Max.
35nS
.
49nS 37nS
.
52nS
32nS 42nS 47nS 35nS 44nS 50nS
0% 0% 2% 0% 0% 2%
DC
12.4uS
20H to
1.28mS
1%
1%
8MHz
12.9uS 13.4uS
20H
2%
2%
1% 2%
DC
12.4uS
20H to
1.28mS
1%
1%
1%
8MHz
12.9uS 13.4uS
20H
2%
2%
2%
6.
Picture tube
Useful diagonal
Model 1492
Inch mm
13
10.83
328
275
Model 2092
Inch mm
20
16
508
406.6
Useful horizontal
Useful vertical
Useful area
Spacing between dot/line trios
Horizontal resolution
Vertical resolution
Interlaced
8.13
86
.015
680
240
480
206.5
558
.39
Pixels
Pixels
Pixels
12
192
.029
550
240
480
304.8
1,239
Deflection angle
Light transmission at center of glass
90°
Approximately
46%
CRT also features: Enhanced contrast, Internal magnetic shield, and
X-Ray output Less than .3mR/hour.
90°
Approximately
.74
Pixels
Pixels
Pixels
46%
7.
Environmental
Operating temperature
Storage temperature
Operating humidity
Storage humidity
0° C
-20° C
20%
10%
70° C
85° C
80%
95%
0° C
-20° C
20%
10%
70° C
85° C
80%
95%
4
The "Drive Signals To The Monitor Input" form is included here for those people who have problems interfacing their drive electronics with the Ceronix Monitor.
DRIVE SIGNALS to the MONITOR INPUT voltage and waveforms, work sheet.
CERONIX
12265 Locksley Lane
Auburn, CA, USA 95602-2055
Company name:
Date:
Drive signal source
Model number:
VIDEO:
For the following measurements use an oscilloscope.
RED GREEN BLUE
With no load the black level voltage is:
With no load the saturated color voltage is:
With 301
Ω
load or other
To GND, or to
Ω voltage V.
load.
}
the black level voltage is: the saturated color voltage is:
If available, sketch the video drive circuit on the back of a copy of this form.
Horizontal or composite sync:
Horizontal frequency: Hz "High" voltage: V
Horizontal sync pulse time: uS "Low" voltage: V
Compare your sync to this table and check the best fit.
For composite sync.
Sketch if different.
Vertical sync:
Vertical frequency: Hz "High" voltage: V
Vertical sync pulse time: uS "Low" voltage: V
Check correct polarity.
Complete form and send to: CERONIX, 12265 Locksley Lane
If there are any questions, call (530) 888-1044.
Auburn, CA. 95602-2055 5
1492 and 2092 Simplified Block Diagram
VIDEO
Output
GAME
SYNC
Output
VIDEO
Interface
Blanking
Isolated
Power
Remote
Controls
VIDEO
Amps.
AUTO BIAS
Vertical Deflection
Horizontal Deflection
Horizontal Size
Control
POWER SUPPLY
CRT
FBT
This block diagram gives a broad view of the circuit organization of the 1492 and 2092 monitors. The blocks with the bold outline represent circuits that are quite different than most other monitors.
The auto bias circuit is designed to actively compensate for picture tube and circuit drift which normally cause the color balance to become unbalanced and also brightness variation. This circuit eliminates the need for the color setup procedure.
The horizontal size control circuit permits the horizontal size to be adjusted from a remote control board instead of a coil on the main board.
It is also used to compensate for pincushion distortion and acts as an anti-blooming circuit by correcting for horizontal size variations which are caused by the additional load on the flyback transformer under high beam current conditions.
The 1492 and 2092 power supplies differ from most other monitors because of their high efficiency switching mode power supply. It is not difficult to troubleshoot if the techniques presented in this manual are clearly understood. Careful reading of all the information presented in this manual will make trouble shooting of the CERONIX monitor no more difficult than any other monitor and maybe even easier.
6
Refer to the block diagram on page 13 (foldout) when reading this description.
A
The Video Interface is designed around a custom IC and will accept positive or negative analog video signals and also 4 line TTL. This IC also has a built in multiplier circuit for the master gain control and blanking.
Resistors are used to protect the IC and to set the gain. The programmed gain is dependent on the input signal amplitude except on TTL. Solder jumpers are used to program the Video Interface for the type of input signal to be received.
The output of the IC drives the video amplifiers. This drive is a current where
0 mA is black and 4.5 mA is a satur`ted color.
B
The Video Amplifiers are of the push pull type. They are built partly on thick films and partly on the PCB. Spreading out the amplifier reduces the component heat and improves the life of the unit. The bandwidth is 8 MHz with 60Vp-p output. The rise and fall times are .04uS.
C
The Beam Current Feedback circuit directs most of the beam current of each amplifier to the beam current buffer. The only time this current is measured by the auto bias circuit is during the time of the three faint lines at the top of the screen and three lines thereafter. The auto bias circuit is designed to adjust the video amplifier bias voltage such that the beam current of each of the three guns is set (programmed), at this time.
D
The Beam Current Buffer converts the, high impedance low current, beam current signal into a low impedance voltage. This voltage is applied to the auto bias IC through a 200 ohm resistor. After the three lines of beam current are measured, the program pulse from the auto bias IC, produces a voltage drop across this 200 ohm resistor that equals the amplitude of the beam current voltage.
7
E
The Auto Bias IC is a combination of digital and analog circuitry.
The digital part is a counter and control logic which steps the analog circuits through a sequence of sample and hold conditions.
The analog part uses a transconductance amplifier to control the voltage on a 10uF capacitor (one per gun). This voltage is buffered and sent to the video amplifhers as the bias voltage. In monitors without auto bias, this voltage has to be set manually using a setup procedure to set the color balance. With the auto bias, the color balance is set during the end of each vertical blanking time.
The control sequence is:
1.
Grid pulse on G1 causes cathode current (3 lines top of screen) which is transmitted by the beam current feedback to the beam current buffer where it is converted to a voltage and applied to the auto bias input pin.
2.
Auto bias IC outputs a reference voltage at its input pin which sets the voltage across the coupling capacitor. This coupling capacitor voltage is directly dependent on beam current.
3.
After the grid pulse is over, the program pulse matches the voltage from the beam current buffer. If the voltage from the beam current buffer, during the grid pulse, is the same as the voltage from the program pulse, the bias is correct and no bias adjustment is made for that vertical cycle.
F
The aging of the picture tube (CRT) not only affects the balance of the cathode cutoff voltage, which is corrected by the auto bias circuit, but it also affects the gain of the CRT. The Auto Bright circuit actively corrects for CRT gain changes by sensing any common bias change from the auto bias circuit and adjusts the screen voltage to hold the average bias voltage constant. The lower adjustment on the flyback transformer is used to set the auto bright voltage to the center of its range. This sets up a second control feedback loop to eliminate picture variation due to the aging of the picture tube.
G
The CRT is a 90° deflection type color picture tube with a 25KV EHT and has integral implosion protection.
8
H
Blanking is accomplished by setting the gain of the interface IC to zero during blank time. The Horizontal Blanking pulse is generated by amplifying the flyback pulse. The Vertical Blanking pulse is started by the vertical oscillator and ended by the counter in the auto bias IC via the "bias out" pulse. The Master Gain control, located on the remote PCB, sets the gain of the video signal when blanking is not active. The Beam Current Limiter circuit, which is designed to keep the FBT from overloading, will reduce the video gain if the average beam current exceeds .75mA.
I
The Sync Interface can be made to accept separate or composite sync. Two comparators are used to receive sync, one for vertical sync and the other for horizontal sync. Resistor dividers are used to protect the comparator IC from over voltage damage.
J
The Vertical Control circuit consists of:
1. Vertical sync circuit.
2. Vertical oscillator.
3. Linear ramp generator.
4. Output control and bias circuits for controlling the power driver.
The active components that make up these circuits, except for part of the bias circuit, are located in the deflection control IC (LA7851). The vertical sync circuit is capable of accepting either positive or negative going sync pulses without adjustment.
The vertical oscillator in the LA7851 is set at 45 Hz and will sync up to 65 Hz without adjustment. The deflection yoke is driven with a linear current ramp which produces evenly spaced horizontal lines on the raster. This linear ramp is generated by supplying a 1uF capacitor with a constant current. The vertical output voltage is held within range (biased) by a timer which partly discharges the 1uF ramp capacitor at the start of vertical retrace. The duration of the timer is controlled by the vertical output voltage and the vertical auto bias circuit.
K
The Vertical Auto Bias circuit greatly increases the range of the bias circuit built into the LA7851. It is made up of a negative peak detector and an amplifier which outputs current to the normal bias circuit, but with a much lower frequency response.
This then eliminates the need for adjustments during production and permits the use of 50Hz and 60Hz vertical sync with only a size adjustment on the remote control board.
K
The aging of the picture tube (CRT) not only affects the balance of the cathode cutoff voltage, which is corrected by the auto bias circuit, but it also affects the gain of the CRT. The Auto Bright circuit actively corrects for CRT gain changes by sensing any common bias change from the auto bias circuit and adjusts the scre en voltage to hold the
9
M
The Horizontal Control incorporates a variable sync delay and a phase locked loop to generate the horizontal timing. The H POS. adjustment on the remote control board sets the sync delay time which controls the picture position.
The phase locked loop uses the flyback pulse to generate a sawtooth wave which is gated with the delayed sync pulse to control the horizontal oscillator.
N
The Horizontal Driver supplies the high base current necessary to drive the horizontal output transistor which has a beta as low as three.
It also protects the horizontal output transistor since it is a transformer and cannot keep the base turned on for longer than its inductive time constant.
O
The Horizontal Output transistor is mounted to the rear frame which acts as a heat sink. The collector conducts 1,000 volt flyback pulses which should not be measured unless the equipment is specifically designed to withstand this type of stress. A linear ramp current is produced in the horizontal yoke by the conduction of the horizontal output transistor (trace time).
A fast current reversal (retrace time) is achieved by the high voltage pulse that follows the turn off of the horizontal output transistor. This pulse is due to the inductive action of the yoke and flyback transformer.
P
The main function of the Flyback Transformer (FBT) is to generate a
25,000 volt (EHT) potential for the anode of the picture tube. This voltage times the beam current is the power that lights up the phosphor on the face of the picture tube. At .75mA beam current the FBT is producing almost 19 watts of high voltage power. The FBT also sources the focus voltage and the filament power. The FBT has a built in high voltage load resistor which stabilizes the EHT, for the low beam current condition. This resistor also discharges the EHT, when the monitor is turned off, which improves the safety of handling the monitor.
Q
The Remote Control PCB houses the:
CONTROL DESCRIPTION CIRCUIT
1. H SIZE ----------- Horizontal raster size --------- Diode modulator
2. V SIZE ----------- Vertical raster size ------------- Vertical drive
3. V RAS. POS. --- Vertical raster position ------- DC current to V. yoke
4. H POS ------------ Horizontal picture position -- H. sync delay
5. M GAIN ---------- Master gain ---------------------- Video interface
10
R
The Horizontal Size Control circuit has four inputs:
# SIGNAL FUNCTION
1. Horizontal size ---------------------- Horizontal size control
2. Beam current ----------------------- Blooming control
3. Vertical linear ramp ---------------- (#4)-(#3)=Vertical parabolic
4. Vertical parabolic + V. linear ramp (Pincushion)
The horizontal size control circuit sums the four signals at one node to produce the diode modulator control voltage.
S
The Diode Modulator is a series element of the horizontal tuned circuit.
It forms a node between GND and the normal yoke return circuit.
If this node is shorted to GND, maximum horizontal size is present.
A diode is used to control the starting time of the retrace pulse at this node.
The reverse conduction time is dependent on the forward current because the current waveform at this node has to exceed the forward current in the diode.
A diode, placed in series with the yoke, is then used to control the retrace pulse amplitude across the yoke. The horizontal size, therefore, is controlled by controlling the current to this diode via the horizontal size control circuit.
T
A Voltage Doubler is used in the power supply for two reasons:
1. To improve the efficiency of the power supply.
2. To permit 120 volt and 220 volt operation. For the 220 volt
operation the voltage doubler is replaced with a bridge rectifier.
U
The Switching Regulator is synchronized to the horizontal pulse and drives a power MOSFET. Unlike most regulators that have a common GND, this power supply has a common V+ and current is supplied from V- to GND.
The MOSFET is connected to V- and signal ground (GND) through a transformer which is used as an inductor for series switchmode regulation.
An operational amplifier, voltage reference, comparator, and oscillator in the power supply controller IC are used to accomplished regulation by means of pulse width modulation.
11
The transformer has two taps on the main winding which are used to generate the +16 volt and +24 volt supplies. It also has a secondary which is referenced to V- and supplies the power supply. Since the power supply is generating its own power, a special start up circuit is built into the power supply controller IC that delays start up until its supply capacitor is charged up enough to furnish the current to start the power supply.
This capacitor is charged with current through a high value resistor from the raw dc supply. This is why the power supply chirps when an overload or underload occurs.
V
The Load consists of the video amplifiers and the horizontal flyback circuit.
The power supply will not operate without the load since the voltage that sustains the power supply comes from a secondary in the power transformer and depends on some primary current to generate secondary current.
W
& X
A separate +12V regulator for the video and the deflection circuits are used in this monitor to minimize raster and video interactions. This also simplifies PCB layout, since the video GND loops are separate from the deflection GND loops.
Y
The Over Voltage Protect circuit is built into the power supply and monitors the flyback transformer peak pulse voltage. This circuit will turn off the power supply and hold it off if the EHT exceeds its rated value. This circuit not only provides assurance that the X-ray specifications are met but also protects the monitor from catastrophic failure due to a minor component failure.
12
1492 & 2092 Monitor Block Diagram
GAME
VIDEO
SYNC
3
VIDEO
Interface
A
3
F.B.P.
V retrace
Beam limit
M. gain
H
SYNC
Interface
I
2
BLANKING
VIDEO
AMPS.
Bias
B
3
Beam
Current
Feedback
C
3
3
3
AUTO BIAS
IC
H. blank
V. blank
Auto
Bright
F
3
D
Beam current buffer
Program pulse
Grid pulse
E
3
CRT
G
V
DY
H
DY
ISOLATION
Transformer
(IN GAME)
V s
VERTICAL
CONTROL
I. V. Feedback
J
VERTICAL
OUTPUT
High Efficiency
L
VERTICAL
AUTO BIAS
K
EHT
HORIZONTAL
CONTROL
H s
Sync delay
H. Pos.
M
V. Size &
V. Ras. Pos.
REMOTE
CONTROLS
(PCB)
Q
H.
Driver
N
H.
Output
O
FBT
PINCUSHION
2
HORIZONTAL
Size Control
R
DIODE
Modulator
Beam Current
S
P
+127V
VOLTAGE
DOUBLER
Raw DC
320V
T
V-
LOAD
(VIDEO & DEFLECTION)
V
-200V
SWITCHING
REGULATOR
Sync
U
+16V
+27V
+12V
Zener
X
Deflection
Supply
OVER
VOLTAGE
PROTECT
Y
+12V
Regulator
W
Video
Supply
13
0
1
2
3
4
5
6
7
8
9
14
AA BB CC DD EE FF GG HH II JJ KK LL MM NN PP RR
8
8
604
Ω
018
G
6
8
6
.1uF
12.1K
023
1N4148
020
301
Ω
021
022
D
301
Ω
004
A
75
Ω
005
7
PN2222
S
909
Ω
054
R
VC
4
RED
INPUT
GND
VC
3
104
340
Ω
024
T
200
Ω
056
1.62K
055
U
412
Ω
057
2.7K
094
032
9
6.8K
15.8K
030 033
6
X
16 13
R o
G o
B o
B
BL
11
62K
016
*
017
3.92K
3.92K
013
003
1.8K
Q
R
10
+12V
3 5 12
TTL M
015
GAIN
Controls XRC5346A
036
GND
4
R
IN
2
J
R
R
1
340
Ω
038
M
G
IN
14
K
G
R
15
340
Ω
035
N
B
IN
7
L
B
R
8
340
Ω
031
O
12.1K
034
604
Ω
044
H
1N4148
042
301
Ω
043
041
E
301
Ω
B
026
75
Ω
027
G
VC
5
GREEN
INPUT
Red Video Amplifier
Green Video Amplifier
106
6.8K
1K
107
1N4148
105
GND
112
340
Ω
037
1.62K
040
Y
.01uF
12.1K
008
197
9
1.82K
C6
0VDC
47V 63uS
4.2-8.2VDC
5-10 17mS
+12V
GND
340
Ω
007
464
Ω
014
I
1N4148
012
2.7K
052
.1uF
025
+12V
.1uF
060
GND
4.42K
051
B
VC
6
301
Ω
010
011
F
C
301
Ω
001
75
Ω
002
BLUE
INPUT
PN2907
053
FG
P
1K
050
FRAME
GND
GND
VC
0
HORIZONTAL
SYNC
H s
TH
4 LINE
TTL INPUT
VC
1
81R
81G
3
GND
1N4005
FBP
1N4005
18
10
101
2.74K
C7
11
103
1.82K
C4
4K
14
C10
6,800pF
108
8
145
5
6
146
+
1/4
LM324
7
12
13
5K
15
4K
3
2
C9
+
1/4
LM324
1
17
16
5K
C11
6,800pF
110
4K
C12
12
13
+
1/4
LM324
14
20
19
5K
GND
C14
6,800pF
111
C15
V s
VC
2
VERTICAL
SYNC
Hs
13
13
7
8.9-9.8VDC
1V 4uS
Blue Video Amplifier
WITH GRID
392
B5
Ω
+12V
1.65K
B11
8
539
Ω
40.2K
B17
20 16
124-126VDC
270
Ω
B14
1N4148
86B
17
2SA
1370
606
Ω
B6
3.78K
B19
B20
1.27K
B8
12
14
3.3pF
1
3
10
SOT
NE592
7
B22
5
8
.1uF
096
5
68K
B1
66
Ω
B15
18
87B
1
.015uF
82B
20
19
510
Ω
B16
180
Ω
B2
2SC3467
4
8.0-9.2VDC
1-2V 4uS
2
510
Ω
89B
83B
27
Ω
3
B00
5.62K
WITH GRID
11
B3
1.8-2.3VDC
270
Ω
B18
+127V
15
.1uF
84B
32
Ω
B13
14
1000pF
88B
FDH400
90B
2SA1370
1.8K
92B
13
80-112VDC
Dark screen
1.5-2.4V
across
85B
1.8K
91B
93B
790
Ω
B9
836
Ω
B10
B12
1.2K
B4
3.32K
B7
GND
Bias Control Line
3
7.4-8.4VDC
81B
VERTICAL BLANKING
+12V
+10V
1.8K
6.8K
138
1.21K
100
MPS A64
129
PN2907
2
139
1 1/2
LM393
+
3
155
1N4148
102
HORIZONTAL
6.4-7.5VDC
8V 63uS
BLANKING
1N4148
6.8K
136
1N4148
134
1.8K
133
0
Ω
124
8
6
7
1.8K
135
1/2
LM393
4
+
5
.047uF
GND
132
1.9-
2.3V
1.8K
156
1.8K
137
1.62K
097
GND
D
098
3.0-3.8VDC
3V 17mS
.1uF
095
20
11
20
11
1N4005
200
Ω
C13
5
68.1K
C2
200
Ω
C16
4
11.5-12.5V
1.8K
046
GND
1.8K
047
270
Ω
045
270
Ω
048
.14-.16V
1K
22K
062
3
2
+
1/2
8
LM393
67
1
5
+
1/2
LM393
6
4
7
+10V
2.7K
154
270
Ω
061
078
6.8K
080
12K
176
1.8K
77
PN2222
153
+4.2V
200
Ω
C8
7
68.1K
C3
68.1K
C1
V. RETRACE
1
RC5
Horizontal
Size
10K
481
RC3
RC2
1K
058
.1uF
128
Vertical
Size
Vertical
Raster
Position
Hs
56pF
198
OUT
7812
GND
IN
130
+16V
1.8K
I1
500
Ω
482
750
Ω
486
1K
483
Horizontal
Position
20K
484
+12V
Master
Gain
1K
485
Remote Control
PCB 490
GND
+12V
VIDEO GAIN LINE
3
+12V
GND
RC4
7.2-8.1VDC
5V 63uS
RC8
RC6
RC7
RC1
LA7830
0
Ω
181
0
Ω
1
174
330
Ω
H1
8
HEAT
SINK
188
0 VDC
2-4V 17mS
1uF
10
330
Ω
H2
20
301
Ω
11
VERTICAL
POWER
AMPLIFIER
GND
192
1
18
+12V
1K
H12
1N4148
88K
H20
200K
H25
3904
H13
Vs
100uF
216
18
Ω
224
202
100uF
VERTICAL OUTPUT
Vo
Retrace
Booster
22K
H15
3906
2
22K
H16
17
18
34K
H10
H5
3.3
Ω
10uF
H24
H23
GND
22K
H14
H22
15
.01uF
207
118K
H4
9
.068uF
220
193
+12V
GND
10uF
068
0
Ω
175
.047uF
.1uF
206
VERT.
OSC.
5.7-6.6VDC
4V 17mS
187
Hp5,2
5.8-6.5VDC
4V 17mS or
127K
200
4
22K
H17
7
18
84K
H3
C
+9Hz
20 19
VERTICAL
V+
VERTICAL
± SYNC INPUT
VERTICAL
OSCILLATOR
500K
H19
-9Hz
200K
H18
.16-.23VDC
5V 17mS
17
B
RETRACE &
BIAS O/S
225
0
Ω
173
2
2.7K
I4
Horizontal
SYNC INPUT
PICTURE
POSITION
O/S
8
7
1 2
7.9-8.5VDC
4.4V 63uS
3
VERTICAL DRIVE
INPUT
COMP.
22-25VDC
25V 17mS
14,6
76.8K
H6
11
330pF
208
Vo
12.4 TO 14V
42V 17mS
3.0-3.8VDC
3V 17mS
4
.7-1.0VDC
.9V
17mS
.047uF
210
13
330
Ω
H7
12
.7-1.2VDC
.9V
17mS
5
56pF
204
1,000pF
205
6
22-25VDC
1V 16mS
11.5-12.5V
1N4742
223
RETRACE
BOOSTER
+27V
1N4005
190
+
200
Ω
, 2W
196
15
4.99K
H9
6-6.4VDC
7
.36-.4VDC
.6V
63uS
1.2VDC
25V 17mS
470uF,50V
191
16
4.75K
H8
DELAYED
SYNC O/S
3
8.2-9VDC
4.4V
63uS
TR .
SAW TOOTH
GENERATOR
4
.1-.3VDC
1.4V
63uS
5
16
V Ref.
MULTIPLIER
BIAS
3.6-4.1VDC
1.6V 63uS
6
0V
15 14
GND
13 12 11
X-RAY
PROTECT
+ comp.
-
LA7851
7
.2V
HORIZONTAL
OSCILLATOR DISCHARGE
63uS
8
4V 63uS
218
9
5.3-6VDC
7.5V
63uS
H. V+
10
17
2.05K
235
12K
I2
22K
I3
GND
+12V
Reverse
Hs
D
8.8K
I12
1,000 pF
226
9
25K
I5
6,10
330pF
227
11
1
6.8K
I13
45K
I6
6,800pF
228
230
+
1uF
+
18
1uF
233
10K
I7
13
.01uF
231
33K
14
I8
1K
15
H.Fo ADJ.
680
Ω
340
Ω
I9
6800pF
232
9.31K
I16 I15
+800Hz +400Hz
I10
G
F
170
Ω
I14
+200Hz
16
E
GND GND
NOTES: POWER SUPPLY VOLTAGES REFERENCED FROM V-
SCOPE GND MUST NOT BE CONNECTED TO GND AND V- AT THE SAME TIME.
0
Ω
160
+27V
GND
+127V
V-
36K
.33uF
183
203
2092
28K
203
10uF
201
+
1K
178
10K
184
10
6
Pincushion correction.
10K
G7
7 5
6
+
1/4
LM324
165
220K
G6
8
7
5
6VDC
4V 17mS
10K
G4
9
4
10K
G3
7.15K
9
10
+
1/4
LM324
172
8
5K
G5
8
6VDC
3V 17mS 2092
68uH
301
H.
Width
220uH
301
2.2K
1/2W
298
1N4005
308
H. Lin.
68uH
302
3,300pF
300
8VDC 23V
70V 250V 63uS
MAX. MIN. H. Size
.47uF
250V
305
2092
.33uF
305
2092
8.2nF
306
1N4005
310
432
.1uF
144
.1uF
122
.1uF
117
1
2
5.8-
6.4V
.047uF
121
3
1.2-
2.5V
.1uF
120
4
5.8-
6.4V
.047uF
118
5
1.2-
2.5V
6
5.8-
6.4V
.047uF
116
7
1.2-
2.5V
.5-.8VDC
.7V
17mS
+10V
AUTO BIAS IC
GND
CA3224E
Vcc
123
Red input
Red hold cap.
sw.
normal comp.
sw. in grid pls. pos.
Green input Green hold cap.
19 sw.
18 comp.
10uF
126
2.5-
6.7V
Blue input sw.
comp.
6V Ref.
33K
152
.1-
.3V
8
CL
Start
Counter
FF Q
BIAS
15
8
20K
C5
2,9
H
B
10
6.3-
7.7V
9
GND
EN
21 H. Line
Counter
CL
Decoder sw. control
11
GRID
PULSE
5V Ref.
Auto
Bias
Active
14
13
PROGRAM
PULSE
12
8.0-9.0VDC
8.4V 17mS
22
21
10uF
20
Blue hold cap.
17
16
127
2.5-
6.7V
10uF
125
2.5-
6.7V
4.6-5.2VDC
1.9-2.3VDC
4V 17mS
3A
FUSE
245
.1uF
150
10
146
+
1/4
LM324
9
33K
141
33K
142
33K
143
246
Inrush
Current
Limit
25-.5
Ω
C-200
240
22K
148
22K
147
8
+127V
C -1.5V
D -3V
6.5-7.5VDC
1
+27V
FR205
*
193K
J1
J13
1
2SA1371E
J14
100K
249
251
250
10.6K
J5
2.33K
6
4.67K
.01uF
20
TZ160B-T3
160V Zener
150uF
250V
317
295
GND
.1uF
250V
294
+
1,000uF
215
INPUT
ERROR
AMP.
16.3-17.8VDC
+15V
16
15
+17V
INPUT
263
.1uF
262
14.8-16.3VDC
18
Ω
248A
2.2nF
254A
FR205
252
220Vo
2
253
CUT
FOR
220Vo
150uF
250V
256
2.2nF
254A
FR205
150uF
250V
257
254
220Vo
260
Ω
J16
130
Ω
J15
B
+3V
A
+1.5V
11K
J2
23.2K
1.8K
273
J3
100K
1/2W
247
7
8,14
90K
J6
100uF
286
6.5-7.5VDC
2
5
4
56K
J4
.5-.8VDC
3
6,800pF
56pF
274
4
3.4-4.2VDC
56pF
276
279
33.2K
J7
6,800pF
277
INPUT
COMP.
Output
Over
Voltage
Protect
}
INPUT
14
6-7VDC
+127V
.022uF
296
V-
.1-.5VDC
5
CONTROL &
FAULT SENSE
4uS
DELAY
COMP.
+
12
13
3.6-4.4VDC
6V 63uS
5.3-5.7VDC
9
5.7-6.3VDC
6
Rx
OUTPUT
.10-.17VDC
1V 63uS
Osc.
Current
SENSE
11
3.5-4.1VDC
3-4V 63uS
330pF
288
7
Cx
DRIVE
10
0VDC
48V 63uS
8
+7.5V
REF.
XRC5184
V-
280
9
2.4-3.6VDC
14V 63uS
V-
J PRA PINS: 3,10,15, & 19
239 255
+16V
+
1,000uF
131
FR205
20
248
.1uF
285
1.00M
J10
17
.1uF
261
3
SMXFR
5
9
4
1 2
258
191K
16
287
38.3K
J9
1,000 pF
291
1.00M
271
18
FR205
260
14.7K
J11
12
15.8K
J12
510
Ω
J8
13
2SK1446LS
18
Ω
MPSA64
270
1N4005
283
268
D
284
2,200pF
282
V-
1.2
Ω
292
+127V
FR205
266
1N4148
290
PC
2
241
115VAC
INPUT
PC
1
238
TC
10
8
Socket Board
PCB 428
TC
6
TC
3
GRID PULSE
*
412
TC
4
FDH400
407
FDH400
408
FDH400
410
100K
416
2SC3675
417
200K
420
1K 1/2W
RED
406
1K 1/2W
GREEN
411
8
6
1K 1/2W
404
BLUE
.015uF 250V
414
10K 1/2W
425
47
100K 1/2W
Ω
415
1/2W
47
Ω
1/2W
424 402
GND
11
12
10 9
470
Ω
1/2W
.68
Ω
405
403
2092
0
Ω
405
FIL.
5
1K 1/2W
422
330pF
423
7
1K
1/2W
413
1K 1/2W
418
4,700pF
421
1
CRT
TC1
431
EHT
VERTICAL
DEFLECTION
YOKE
NO DVM
1KV 63uS
TC2
YC1
18
1,000uF 35V
+
195
19
2SC3467
V
RAS. POS.
0 TO 7 VDC
1K
H11
180
GND
150
Ω
1/2W
182
.01uF
209
YC2
433
390
Ω
2SC4159E
, 2W
236
12.7VDC
33V 63uS
19
20
Horizontal Drive
Transformer
2
237
100
Ω
I11
2,200pF
234
1
3
4
157
FR205
293
+12V
GND
HORIZONTAL RASTER ADJ.
FR205
HR
314
HL
470
Ω
,1/2W
270
Ω
, 2W
VERTICAL LINEARITY
Z
309 303
312
2SD1651
304
+127V
10
9
6
8
FLYBACK
TRANSFORMER
EHT
FOCUS
GND
7
3
SCREEN
4
5
Beam
Current
FIL.
1
FIL.
V-
2
CPT1500
GND
297
0
Ω
289
PN2222
Beam current limiter circuit.
+6V 270
Ω
MPSA64
62K
071 D
65A
063
750
Ω
064
.1uF
069
065
GND
+
62K
070
10uF
066
3.3K
179
1.8K
159
.047uF
162
19
2092
36K
166
12K
166
H. Pincushion
Parabolic
2092
22K
167
1.82K
G17
20
28K
Blooming correction.
H. Width Adj.
+
+6V
100uF
169
G12
.01uF
163
100K
G10
62K
166A
50K
G9
8.87K
167
Linear
HORIZONTAL YOKE
433
YC3
127VDC
150V 300V
YC4
MAX. MIN.
H. Size
.01uF
1.5KV
306
HEAT
SINK
267
200pF
265
150
Ω
264
GND
CC1
CC2
4
3
10K
G2
10K
G1
H
SIZE
+12V
2
3
4
+
1/4
LM324
11
2, 12 GND
LEGEND
1
1
+6V LINE
19
6.8K
171
BF5ROM
125
Optional
244
Dual Posistor Optional.
246
No.
LTR.No.
X
X-
Y V
X
X-Y VDC
X-Y VDC
Vp-p TIME
WAVEFORM
BOARD PART No.
PART No. ON PRA.
PRA PIN No.
DC VOLTAGE
RANGE, USING
A DMM.
AC VOLTS
Peak to Peak
CYCLE
TIME
Measured with scope
38.3K
G11
*
164
6.8K
.1uF
161
G16
13
8VDC 22V
4V 12Vp-p 17mS
MAX. MIN. H. Size
44.2K
18
12
13
+
1/4
LM324
G13
14
16K
17
.01uF
2SC4159E
2.2K
15
G14
16
185
14
0
Ω
278
HEAT
SINK
186
G15
168
CERONIX
NONE
SCALE:
DRAWN BY:
F. H.
DATE & REV.
1/8/88
1/16/88
3/11/88
750uH
316
2.7uF
315
12265 Locksley Lane
Auburn, California 95602-2055
5/21/88
11/12/90
2/12/98
DRAWING
NUMBER
1N4937
311
.022uF
630V
307
CERONIX MODEL 1492 MONITOR CIRCUIT
2ED0114-E
AA BB CC DD EE FF GG HH II JJ KK LL MM NN PP RR
15
0
1
2
3
4
5
6
7
8
9
VIDEO INTERFACE CIRCUIT DESCRIPTION (+ & - Analog)
The video interface circuit is a general purpose RGB type input circuit. This circuit connects the external video signal to the video amplifiers. It can accept positive going analog, negative going analog, and 4 line TTL. The particular mode of operation is selected by placing solder bridges on the foil side of the PCB. The solder bridge patterns are given in appendix A. Simplified video interface circuit:
Black Level (5.6V)
1. NEGATIVE GOING ANALOG MODE.
+12V
RED channel shown
Saturated Color (1V)
16
VIDEO
AMPS
7.5V BIAS LINE
2.2V
R,G,&B
VIDEO
INPUTS
20
301
Ω
604
Ω
2
21 18
3
62K
6.3V
C5346
36
-Analog Black Level (-A BL)
200
Ω
3.6K
Connections Installed
ALWAYS NORMALLY
Q & Y S & X
MG
12 MASTER
GAIN&
BLANKING
16
R
In the negative analog mode, the video signal has a black level which is the -A BL voltage.
The saturated color is the lowest input voltage (.9V-1.1V). To prevent input line ringing master gain voltage.
Saturated Color (1.6V or 3.2V)
2. POSITIVE GOING ANALOG MODE.
Black Level (.27V)
15.8K
11
7.5V BIAS LINE
+12V
RED channel shown
16
VIDEO
AMPS
+ANALOG ENABLE
33
R,G,&B
VIDEO
INPUTS
D
301
Ω
21
+12V
2
C5346
36
200
Ω
3.6K
Connection Installed
ALWAYS NORMALLY
Y
D,E,F,G,H,I,
J,K,L,P, & T
MG
12
MASTER
GAIN &
BLANKING
A
12.1K
23
75
Ω
05
301
Ω
04
340
Ω
J
3
340
Ω
24
38
M
In the positive analog mode, a bias current flows to the input which is set by resistor
33 at the +Analog Enable input. This current produces a voltage, across the parallel resistance
With a bias resistor of 15.8K, the bias current is .6mA. If the external source resistance is
300 ohms, the black level voltage at pin 2 is .27V. A black level voltage of .3V is set by screen when the video input connector is disconnected. The saturated color is the highest input voltage. There are two standard, saturated color,
16
VIDEO INTERFACE CIRCUIT DESCRIPTION (TTL)
3. 4 LINE TTL MODE.
+12V
7.5V BIAS LINE
RED channel shown
16
R,G,&B
VIDEO
INPUTS
INTENSITY
INPUT
15.8K
11
33
+ANALOG EN. &TTL
+12V
905
Ω
18 21
2
1K (Optional)
04
+12V
GND
200
Ω
2.7V
C5346
36
3.6K
Connections Installed
ALWAYS NORMALLY
None
A, B, C,
P, & T
MG
12
5
3.92K
03
1.87K
3.92K
13
VIDEO
AMPS
MASTER
GAIN &
BLANKING
15
In the 4 line TTL mode the red, green, and blue video lines will pass color when high.
The intensity of the color is set by the fourth TTL line. Saturated color is displayed when the intensity line is high or open, and when it is low, the displayed color is half intensity.
Although the R, G, and B lines are logic lines, the intensity line is an analog line.
To insure full saturated color, the TTL driver to the intensity line should have no other loads.
The, 1K to GND, input resistor on the color lines may be installed to keep the screen dark when no video input cable is connected. The logic 0 voltage at the input is 0 to .4V @ .6mA.
The logic 1 voltage at the input is 2.7V to 5.5V @ -2.1mA with the 1K pulldown and .6mA without.
Refer to the video interface schematic to the right for the following component description.
Both the blanking and the gain control is accomplished by the Master Gain line to the video programmable voltages for setting the max. MG voltage. The video gain is also affected by gain for the -Analog mode and provide protection to the video interface IC inputs in the programmed in. A clamp circuit is used in the -Analog mode to reduce the effect of line ringing. this clamping function. P is bridged to reference the clamp to GND for the +Analog and TTL override the chip resistor tolerance. The black level for the blue channel may be increased for each of the three input modes. These modes are selected by bridge points Q & Y .
17
VIDEO INTERFACE SCHEMATIC
To
Video
Amps.
P.S.
Master Gain line (MG)
S
909
Ω
054
T
U
200
Ω
412
Ω
056
1.62K
055
057
2.7K
094
1.5K
040
Y
4.2-8.2VDC
5-10 17mS
.1uF
+12V
GND
032
6.8K
15.8K
030 033
X
16 13 9 6 11
R o
G o
B o
B
BL
62K
016
*
017
3.92K
3.92K
013
003
1.87K
Q
10
+12V
3
R
5 12
TTL
Controls C5346
015
M
GAIN
036
GND
4
R
IN
2
R
R
1
G
IN
14
G
R
15
B
IN
7
B
R
8
J
340
Ω
038
M K
340
Ω
035
N
L
340
Ω
031
O
12.1K
340
Ω
023 024
12.1K
340
Ω
034 037
12.1K
340
Ω
008 007
R
VC
4
604
Ω
018
G
1N4148
020
301
Ω
021
022
D
301
Ω
004
A
75
Ω
005
RED
INPUT
G
VC
5
604
Ω
044
H
1N4148
042
301
Ω
043
041
E
301
Ω
026
B
75
Ω
027
GREEN
INPUT
464
Ω
014
I
1N4148
012
2.7K
052
.1uF
025
+12V
.1uF
060
GND
4.42K
051
301
Ω
011
010
F
301
Ω
001
C
75
Ω
002
PN2907
053
FG
FRAME
GND
P
1.00K
050
GND
B
VC
6
BLUE
INPUT
VC
0
HORIZONTAL
SYNC
TH
4 LINE
TTL INPUT
18
VIDEO AMPLIFIER CIRCUIT, FUNCTION, DESCRIPTION
The video amplifier, is a high speed push pull amplifier, which can swing as much as 92 volts.
The maximum dynamic output swing is limited to 60 volts. The rest of the output voltage range is reserved for bias adjustment.
+127V
SIMPLIFIED VIDEO AMPLIFIER CIRCUIT:
270
Ω
B14
2SA1370
66
Ω
B15
+12V
87B
VIDEO
INTERFACE
C5346
392
Ω
B5
606
Ω
B6
790
Ω
B9
40.2K
1.65K
B11
836
Ω
B10
1
+
NE592
B17
7
14
5.62K
B12
68K
B1
.015uF
82B
2SC3467
From Auto Bias control output
83B
27
Ω
B3
+7.9V line
The video amplifier's output voltage, With no input signal, is the black level which is the picture tube cut off voltage. This voltage is set for each of the three video amplifiers by the auto bias circuit. This black level voltage has a range of 80V to 112V.
The voltage swing at the output is 60 volts for a 4.3 mA current signal from the C5346.
For this same 4.3 mA current signal the voltage swing at the video amp. input is 1.32 volts and the
-input voltage swing at the NE592 is .75 volts. The reason for using the voltage matching resistor
B6
is that the C5346 minimum output voltage is 7.7 volts, and the bias voltage at the NE592 input is 5.3 volts.
VIDEO AMPLIFIER CIRCUIT DESCRIPTION
The control circuit for the video amplifier is located on the B PRA (B precision resistor array).
The B PRA includes all the resistors and the NE592. All of the parts labeled
Rxx
, xxG
, and xxB
, are components located on the circuit board, which are part of the red, green, and blue video amplifiers.
The video amplifier's stability and precise response to the input signal comes from a combination of the geometric layout of the B PRA and the high frequency response of the NE592.
The NE592 stabilization capacitor
B00
is an integral part of the B PRA conductor layout.
Resistor
B 4
is used to boost the NE592 drive current to the PNP transistor
87B
.
The NE592 bias circuit, at the input side, consists of
B 5
,
B6
, and
B 9
.
The negative feedback bias resistors are,
B11
,
B10
, and
B 12
with
B 17
as the output feedback resistor. Resistors
B19
and
B20
are connected to solder pads which, when bridged, permit the 1492 B PRA to be used on the models 1490 and 1491 monitors.
The NE592 gain is set by resistor
B8
. The drive signal from the NE592,
B22
pin 7, is coupled to the base of the NPN transistor
83B
through an impedance matching resistor
B2
.
This drive is also coupled to the base of the PNP transistor
87B
via a coupling capacitor
82B
.
The NE592 output voltage range is 6V to 10V, which is the reason for the 7.9 volt NPN bias line.
The 7.9 volt bias line is generated by buffering a voltage divider, formed by resistors
97 and
100
, with a PNP darlington transistor
98
. A capacitor
9 5
is connected to shunt the high current spikes to GND. This line is common to all three video amplifiers.
The AC current gain is set by resistor
B3
for the NPN output transistor and by
B13 for the PNP output transistor which is AC coupled via a capacitor
84B
. On a positive output transition of the video amplifier, the current of the PNP transistor can go as high as 32mA and on a negative transition the current drops to 0mA
19
8
6 7
VIDEO AMPLIFIER SCHEMATIC
8.9-9.8VDC
1V 4uS
Blue Video Amplifier
WITH GRID
392
B5
Ω
+12V
1.65K
B11
8
539
Ω
B20
1
3
10
40.2K
B17
20
124-126VDC
270
Ω
B14
16
1N4148
86B
5
68K
B1
66
Ω
B15
17
2SA
1370
18
87B
1
.015uF
82B
20
19
510
Ω
B16
606
Ω
B6
1.27K
B8
12
14
SOT
NE592
7
B22
8
3.78K
B19
3.3pF
B00
5
.1uF
096
5.62K
180
Ω
B2
2SC
3467
4
8.0-9.2VDC
1-2V 4uS
2
510
Ω
85B
83B
27
Ω
WITH GRID
B3
11
3
1.8-2.3VDC
270
Ω
B18
+127V
15
.1uF
84B
32
Ω
B13
14
1000pF
88B
FDH400
90B
2SA
1370
13
80-112VDC
Dark screen
1.5-2.4V
across
85B
2.2K
92B
PART OF
AUTO BIAS
2.2K
790
Ω
B9
836
Ω
B10
B12
GND
1.2K
B4
3.32K
B7
91B
93B
BIAS CONTROL LINE
3
7.4-8.4VDC
81B
+12V +12V
+12V
VIDEO INTERFACE
MG
VERTICAL and
HORIZONTAL
BLANKING,
Master Gain, &
Beam limiter
1.21K
100
MPS A64
D
098
1.62K
097
GND
.1uF
095
GND
R G B
VIDEO SOURCE (external)
For low output distortion, the PNP transistor is biased with a 6 mA current. The NPN transistor and resistor
B 17
conduct the PNP bias current to GND. Diode
86B
balances the
PNP base to emitter voltage. Resistors
B1
and
B14
set the voltage across
B 15
which define the video amplifier output stage bias current. A quick way to check this current, is to measure the voltage drop across the 510 ohm
85B
. The permissible voltage range is listed on the schematic as 1.5-2.4V. The PNP and NPN collector resistors
B16
and
85B help stabilize the amplifier and provide some arc protection. Resistor
B 18
is used to decouple the video amplifiers from the +127V line. Capacitor
96
is used to decouple the +12 volt line close to the video amplifiers. If this capacitor or the 7.9V line capacitor
095
is open, the video may be unstable and distorted. Resistor
B7
is the auto bias output load resistor.
If there is a problem with the video, first check the output waveform of the video amplifier, with the oscilloscope, if ok the problem is not in the video section. If not ok, check the input waveform at B PRA pin 8, if not ok there, check the video interface, If ok at the video amplifier input, refer to this section to help with analyzing the video amplifier problems.
20
SOCKET BOARD , DEGAUSSING CIRCUIT, AND LEGEND DESCRIPTION
TC
10
8
432
Socket Board
PCB 428
TC
6
FDH400
1K 1/2W
RED
407
FDH400
406
1K
1/2W
8
10
GREEN
411
6
408
FDH400
1K
1/2W
404
BLUE
11
12
410
TC
3
GRID PULSE
*
412
.1uF 250V
414
10K 1/2W
470
Ω
1/2W
403
9
.68
Ω
405
2092
0
Ω
405
5
1K
1/2W
422
7
1K
1/2W
413
1
431
EHT
TC
4
100K
416
2SC3675
417
47
Ω
425
100K 1/2W
415
47
Ω
1K
1/2W
418
330pF 2,200pF
423 421
EHT
FOCUS
SCREEN
FBT
200K
420
424 402
FIL.
TC1
GND
FIL.
FIL.
TC2
The primary function of the socket board is to connect the main board to the CRT and to protect the main board against arc related voltage spikes which originate in the CRT.
The tube socket has built in spark gaps which direct part of the arc energy to the tube ground (aquadag) through a dissipation resistor
403
. The remaining high voltage from an arc is dropped across current limit resistors: Resistors
404
,
406
, and
411
and diodes
407
,
408
, &
410
protect the video amplifiers by directing the arc energy to capacitor
414
. Since arcing does not normally occur in rapid succession, capacitor
414 is left to discharge by the leakage current of diodes
407
,
408
, &
410
and zener
{
CC1
CC2
BF
5ROM
125 diode
412
is not normally used. The grid pulse transistor is protected by a low pass filter made up of resistors
422
&
425
and capacitor
423
. The auto bright transistor
417 is protected by resistors
416
&
420
and by a low pass filter comprised of resistors
413
,
418
, &
415
and capacitor
421
. Resistors
402
&
424 reduce the arc energy from the tube ground to signal GND.
3A FUSE
The current gain of the auto bright control loop is set by resistor
420
.
The filament current is fine tuned by resistor
405
.
The degaussing coil
432
is energized when power is turned on.
It then rapidly turns off due to the heating of posistor
244
.
245
Legend Description
241
PC
2
115VAC
INPUT
No.
Represents the 1492 board part number. The parts list gives the
CERONIX PART NUMBER which is indexed to the board part number.
244
PC
1
238
LTR.No.
Part numbers of the resistors on the PRA indicated by LTR.
LEGEND
X
X-
Y V
X
X-Y VDC
X-Y VDC
Vp-p TIME
{
PRA pin number. To determine which PRA the pin number belongs to, look for the nearest PRA part number on that line.
DC voltages are measured to GND except in the power supply where V- is the reference. Use a DVM for DC measurements.
WAVEFORM
{
TIME is the cycle time of the waveform.
The waveform is normally checked with a oscilloscope.
It has a P-P voltage amplitude of
Vp-p
.
No.
LTR.No.
BOARD PART No.
PART No. ON PRA.
X
X-
Y V
X
X-Y VDC
X-Y VDC
Vp-p TIME
WAVEFORM
PRA PIN No.
DC VOLTAGE
RANGE, USING
A DMM.
AC VOLTS
Peak to Peak
CYCLE
TIME
Measured with scope
CAUTION: When making measurements on the power supply be sure that the other scope probe is not connected to GND.
21
BLANKING AND MASTER GAIN CIRCUIT, FUNCTION, DESCRIPTION
Blanking in this monitor is accomplished by reducing the video gain to zero during the vertical and horizontal blank time. During video time, the gain is set by the master gain control which is located on the remote control PCB. If the overall beam current exceeds .75mA for more then ten frames, the beam current limiter circuit will reduce the video gain to protect the FBT.
SIMPLIFIED GAIN CONTROL CIRCUIT:
+12V
1K
MASTER GAIN
485
1K
58
GAIN SELECT
RESISTORS
VIDEO GAIN LINE
HORIZONTAL BLANKING
FLYBACK PULSE
0VDC
47V 63uS
SIGNAL
CONDITIONING
CIRCUIT
PN2222
104
VIDEO INTERFACE
C5346
36
+12V
3.6K
200
Ω
+7.5V
One of three input circuits.
+
Video
Amp.
To
CRT
BIAS ACTIVE
HIGH Z
+2V
5
Vertical Bias O/S
+2V
6
+
1/2
LM393
155
7
VERTICAL BLANKING
2
1N4148
134
3
1/2
LM393
+
.047uF
132
1
63
BEAM CURRENT LIMITER
+6V
PN2222
MPSA64
D
65
Total
beam current
10uF
66
From FBT
The video P-P voltage amplitude at the cathodes, is the video input signal amplitude times the master gain control setting times the video amplifier gain. The gain select resistors set the maximum video gain via the master gain line. For a greater range of brightness,
(highlighting) the video system is allowed to supply high peak video currents which could damage the FBT if sustained. The beam current limiter circuit insures that the long term maximum beam current is not exceeded.
Horizontal blanking is achieved by amplifying the flyback pulse (FBP) with transistor
104
.
Vertical blanking starts as soon as the LA7851 starts the vertical retrace sequence and is terminated by the auto bias, bias active signal. A comparator is used to sense the vertical bias
O/S, at pin 16 of the LA7851, which goes low when vertical retrace starts. Capacitor
132 holds the vertical blanking active, between the vertical bias O/S pulse, and the bias active pulse.
When the bias active line goes high, the capacitor
132
is reset and vertical blanking ends, after the bias active line returns to it's high impedance state.
22
BLANKING AND MASTER GAIN CIRCUIT DESCRIPTION
The master gain control
485
is connected to the video gain line through a 1K resistor
58
. The voltage range of the video gain line is programmable via resistor
094 and solder bridges at
S
,
T
, &
U
which may connect resistors
54
,
55
,
56
, and
57
to the video gain line. This arrangement permits a variety of input signals and picture tubes to be used with the same monitor PCB.
Horizontal blanking ( ) is added to the gain line by transistors
104
. This transistor pulls down on the gain line through diode
102
when the flyback pulse is high.
Capacitor
197
is charged by diodes
105
,
106
and resistor
112
such that, as soon as the flyback pulse starts going positive the NPN transistor
104
turns on and horizontal blanking starts. The time constant of capacitor
197
and resistors
112
and
107
is chosen such that the capacitor will lead the FBP on the downward slope and turn the horizontal blanking transistor off just at the end of the FBP.
Vertical blank time is started when a low going pulse from the LA7851 pin 16 causes the output, pin 7, of the dual comparator
155
to go low. Capacitor
132
is discharged through resistor
135
at this time. After the end of the LA7851 pulse, the capacitor
132 holds the output, pin 1 of the comparator, low until the bias active pulse recharges the capacitor
132
through diode
134
. During the high time of the bias active pulse, the second comparator output is still low, because of the voltage drop across the diode
134
.
The end of vertical blank time occurs when the bias active line returns to it's high impedance state. The capacitor
132
holds the charge from the bias active pulse until the next vertical blank time.
The video gain line will source up to 32mA during blank time, which is the reason for buffering the vertical blank comparator with a PNP transistor
139
and E-B resistor
129
.
Resistors
137
and
138
supply a voltage that is midrange relative to the LA7851 pulse for maximum noise immunity. Resistors
133
and
136
also supply another midrange voltage for the bias active pulse and the, vertical blanking, hold capacitor to work against.
Resistors
124
and
156
are used as jumpers.
The beam current limiter circuit uses the base to emitter voltage of a darlington transistor
65
to set the maximum beam current. The beam current is converted to a voltage across resistor
G17
. This voltage is applied to a long time constant RC circuit, resistor
70
and capacitor
66
, before it is sensed by the darlington transistor.
Resistor
65 A
has been added to protect the darlington transistor from arc energy.
The sharpness of the limiting response is set by resistors
64
and
71
.
Transistor
63
then, reduces the video gain by pulling down on the master gain line upon excessive beam current.
23
BLANKING AND MASTER GAIN SCHEMATIC
VIDEO GAIN LINE
4.2-8.2VDC
5-10 17mS
1K
058
RC2
Remote control PCB
+12V
MASTER
GAIN
1K
485
GND
VERTICAL BLANKING
1.8K
129
MPS2907
2
139
1
1/2
LM393
+
3
155
1N4148
102
HORIZONTAL
6.4-7.5VDC
8V 63uS
BLANKING
1N4148
6.8K
136
1N4148
134
1.8K
133
GND
+10V
0
Ω
124
8
6
7
1.8K
135
1/2
LM393
+
5
4
.047uF
132
6.8K
138
1.9-
2.3V
1.8K
156
1.8K
137
PN2222
104
106
6.8K
107
1N4148
105
1K
.01uF
112
197
H
B
GND
TO AUTO BIAS IC
FROM AUTO BIAS SUPPLY
(BIAS ACTIVE)
From auto bias IC pin 13
1.9-2.3VDC
4V 17mS
(VERTICAL BIAS O/S)
From LA7851 pin 16
3.0-3.8VDC
3V 17mS
(FLYBACK PULSE)
From FBT pin 8
0VDC
47V 63uS
GAIN SELECT RESISTORS
S
909
Ω
054
T
U
200
Ω
412
Ω
057 056
1.62K
055
+12V
1.62K
040
10K
094
GND
M
GAIN
C5346
036
VIDEO INTERFACE IC
FBT
BEAM CURRENT LIMITER CIRCUIT.
+6V 270
Ω
MPSA64
PN2222
071
D
62K
065A
065
+
063
750
Ω
064
GND
62K
10uF
066
070
+6V
1.8K
GI7
EHT
Return
24
Board No.s 001 to 100 REPLACEMENT PARTS LIST Models 1492 and 2092
CERONIX
PART No.
DESCRIPTION
CERONIX
PART No.
DESCRIPTION
025
026
027
028
029
030
031
032
017
018
019
020
021
022
023
024
009
010
011
012
013
014
015
016
001
002
003
004
005
006
007
008
041
042
043
044
045
046
047
048
049
050
033
034
035
036
037
038
039
040
CPR0128
CPR0124
CPR0140
CPR0128
CPR0124
CPS1754
CPR0129
CPR0144
CPR0128
CPD1251
CPR0140
CPR0131
CPR0011
CPR0018
CPR0132
CPD1251
CPR0128
CPR0144
CPR0129
CPC1039
CPR0128
CPR0124
CPR0050
CPR0013
CPR0129
CPC1039
CPR0145
CPR0144
CPR0129
CPI1409
CPR0129
CPR0129
A1
A1
B1
B1
B1
C1
A2
A2
C2
C2
C2
C2
A2
B1
B2
B2
B2
B2
B1
B1
B1
B2
A2
A2
A2
B1
BB8
BB8
BB8
BB6
BB7
BB6
BB6
BB6
AA7
A2
A2
A2
A2
B3
B2
B2
B2
B2
BB9
BB9
CC6
AA9
AA9
BB7
BB7
AA8
AA8
AA8
AA7
AA7
CC8
BB9
BB9
AA6
BB7
AA5
AA6
AA7
BB7
AA6
BB7
AA7
301 ohm ±1%, .25W
75 ohm ±1%, .25W
3.92K ohm ±1%, .25W
301 ohm ±1%, .25W
75 ohm ±1%, .25W
6 Conductor Header.
340 ohm ±1%, .25W
12.1K ohm ±1%, .25W
Optional input filter capacitor.
301 ohm ±1%, .25W
1N4148 10mA, 75V Diode
3.92K ohm ±1%, .25W
464 ohm ±1%, .25W
1.8K ohm ±5%, .25W
62K ohm ±5%, .25W
Optional -BL adjust resistor.
604 ohm ±1%, .25W
1N4148 10mA, 75V Diode
301 ohm ±1%, .25W
Optional input filter capacitor.
12.1K ohm ±1%, .25W
340 ohm ±1%, .25W
.1uF ±5% @ 50V
301 ohm ±1%, .25W
75 ohm ±1%, .25W
0 ohm Jumper
6.8K ohm ±5%, .25W
340 ohm ±1%, .25W
.1uF ±5% @ 50V
15.8K ohm ±1%, .25W
12.1K ohm ±1%, .25W
340 ohm ±1%, .25W
XRC5346A Custom Video IC
340 ohm ±1%, .25W
340 ohm ± 1%, .25W
CPR0136
CPD1251
CPR0128
CPR0132
CPR0004
CPR0011
CPR0011
CPR0004
C2
D1
D1
D1
D1
B2
C2
C2
C2
BB5
BB8
AA8
AA8
AA7
DD8
CC8
CC9
DD8
1.62K ohm ±1%, .25W
Optional input filter capacitor.
1N4148 10mA, 75V Diode
301 ohm ± 1%, .25W
604 ohm ±1%, .25W
270 ohm ±5%, .25W
1.8K ohm ±5%, .25W
1.8K ohm ±5%, .25W
270 ohm ±5%, .25W
CPR0009 D1 CC9 1K ohm ±5%, .25W
.01
.01
.01
.01
.01
.05
.01
.01
.01
1.51
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
.05
.01
.01
.01
.01
.22
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
90B
91B
92B
93B
094
095
096
097
82B
83B
84B
85B
86B
87B
88B
89B
098
099
100
074
075
076
077
078
079
080
81B
066
067
068
069
070
071
072
073
059
060
061
062
063
064
065
065A
051
052
053
054
055
056
057
058
CPR0141
CPR0012
CPQ1301
CPR0126
CPR0136
CPR0127
CPR0130
CPR0009
CPR0011
CPR0009
CPR0013
CPR0500
CPC1040
CPQ1308
CPC1037
CPR0050
CPD1251
CPQ1309
CPC1005
CPR0006
CPD1250
CPQ1309
CPR0011
CPR0011
CPR0012
CPC1039
CPC1039
CPR0136
CPQ1302
CPC1039
CPR0004
CPR0015
CPQ1303
CPR0007
CPQ1302
CPR0018
CPC1101
CPI1410
CPC1101
CPC1039
CPR0018
CPR0004
CPR0134
D1
C1
C2
D2
D2
D2
D2
C2
CC8
CC8
CC8
AA5
AA5
AA5
BB5
EE3
D2
D2
D2
D2
E1
E2
D1
E2
D1
D1
D1
D1
E2
E1
E1
E1
E1
E1
E1
E2
RR5
DD8
GG2
PP5
RR5
PP5
CC8
DD9
DD8
PP5
PP5
PP5
RR5
EE9
EE8
E1
C3
A3
A3
C3
B3
C3
C3
C3
C3
C3
C3
C3
C4
B3
A3
B3
A4
A4
DD8
CC1
CC1
CC2
DD1
CC1
CC1
DD2
CC2
DD2
DD2
DD2
DD2
BB5
DD3
BB2
CC3
DD3
B4 CC3
4.42K ohm ±1%, .25W
2.7K ohm ±5%, .25W
PN2907 .6A, 40V, .6W, PNP
909 ohm ±1%, .25W
1.62K ohm ±1%, .25W
205 ohm ±1%, .25W
412 ohm ±1%, .25W
1K ohm ±5%, .25W
.1uF ±5% @ 50V
270 ohm ±5%, .25W
22K ohm ±5%, .25W
PN2222A .6A, 30V, .5W, NPN
750 ohm ±5%, .25W
MPSA64 .3A, 30V, D-PNP
62K ohm ±5%, .25W
10uF ±20% @ 50V
LM393 Dual Comparator
10uF ±20% @ 50V
.1uF ±5%, @ 50V
62K ohm ±5%, .25W
270 ohm ±5%, .25W
1.8K ohm ±5%, .25W
1K ohm ±5%, .25W
6.8K ohm ±5%, .25W
Blue Video Amplifier
.015uF ±10% @ 250V
2SC3467AE .1A, 200V, 1W, NPN.
.1uF ±10% @ 250V
0
Ω
Jumper
1N4148 10mA, 75V Diode
2SA1370E .1A, 200V, 1W, PNP
1000pF ±20% @ 500V
510 ohm ±5%, .25W
FDH400 .1A, 200V, Diode
2SA1370E .1A, 200V, 1W, PNP
1.8K ohm ±5%, .25W CF
1.8K ohm ±5%, .25W CF
2.7K ohm ±5%, .25W
.1uF ±5% @ 50V
.1uF ±5% @ 50V
1.62K ohm ±1%, .25W
MPSA64 .3A, 30V, D-PNP
1.21K ohm ±1%, .25W
.01
.01
.03
.19
.01
.01
.01
.05
.05
.01
.08
.01
1.12
.07
.16
.07
.01
.01
.19
.03
.01
.01
.01
.01
.01
.01
.01
.01
.06
.01
.04
.31
.04
.05
.01
.01
.05
.01
.01
.05
.01
.08
.01
25
Board No.s 101 to 200 REPLACEMENT PARTS LIST Models 1492 and 2092
CERONIX
PART No.
DESCRIPTION
CERONIX
PART No.
DESCRIPTION
125
126
127
128
129
130
131
132
117
118
119
120
121
122
123
124
109
110
111
112
113
114
115
116
101
102
103
104
105
106
107
108
141
142
143
144
145
146
147
148
133
134
135
136
137
138
139
140
149
150
151
152
CPD1252
CPD1251
CPD1252
CPQ1303
CPD1251
CPD1251
CPR0013
CPC1028
CPC1028
CPC1028
CPR0009
C5
C5
D5
DD7
DD7
BB4
6800pF ±10% @ 100V
6800pF ±10% @ 100V
1K ohm ±5%, .25W
CPS1756
CPR0506
CPC1036
CPC1039
CPC1036
CPD1251
CPR0011
CPR0013
CPR0011
CPR0013
CPQ1301
CPR0050
CPR0016
CPR0016
CPR0016
CPC1039
CPD1252
CPI1405
CPR0015
CPR0015
CPC1039
CPC1036
CPC1039
CPI1402
CPR0050
CPC1101
CPC1101
CPC1101
CPC1039
CPR0011
CPI1407
CPC1104
CPC1036
CPR0011
CPC1039
CPR0050
CPR0016
A5
A5
B5
B5
B5
B5
B4
C5
D4
C5
A5
B5
B5
C6
C6
C6
C6
C7
C7
C6
A6
B6
C5
C5
C6
C6
B7
C7
C7
C7
A7
A6
A7
B7
A6
B6
B6
B6
B5
B5
B5
A6
C6
D6
C6
DD5
AA4
DD5
AA4
BB4
BB4
BB4
DD6
EE7
EE7
EE7
EE6
EE6
EE6
FF7
CC3
FF7
FF6
FF6
EE3
AA3
EE3
JJ6
BB4
BB4
BB3
BB4
BB3
CC4
CC3
AA3
GG6
GG7
GG7
EE5
DD5
GG6
GG6
GG6
GG5
1N4005 1A, 600V, R-Diode
1N4148 10mA, 75V, Diode
1N4005 1A, 600V, R-Diode
PN2222A .8A, 40V, .5W, NPN
1N4148 10mA, 75V, Diode
1N4148 10mA, 75V, Diode
6.8K ohm ±5%, .25W
6800pF ±10% @ 100V
"TC" 10 Conductor Header
"C" PRA (Auto Bias)
.047 uF ±5% @ 50V
.1 uF ±5% @ 50V
.047uF ±5% @ 50V
.1uF ±5% @ 50V
.047uF ±5% @ 50V
.1uF ±5% @ 50V
CA3224E Auto Bias IC
33K ohm ±5%, .25W
33K ohm ±5%, .25W
.1uF ±5% @ 50V
1N4005 1A, 600V, R-Diode
LM324 Quad Op. Amp.
22K ohm ±5%, .25W
22K ohm ±5%, .25W
.1uF ±5% @ 50V
0 ohm Jumper
EE8 33K ohm ±5%, .25W
.03
.03
.01
0 ohm Jumper.
10uF ±20% @ 50V
10uF ±20% @ 50V
10uF ±20% @ 50V
.1uF ±5% @ 50V
1.8K ohm ±5%, .25W
NJM7812FA 12V, 1A, Regulator.
1000uF ±20% @ 35V
.047uF ±5% @ 50V
1.8K ohm ±5%, .25W
1N4148 10mA, 75V, Diode
1.8K ohm ±5%, .25W
6.8K ohm ±5%, .25W
1.8K ohm ±5%, .25W
6.8K ohm ±5%, .25W
.05
.01
.30
.22
.04
.01
.01
.01
.01
.01
.01
MPS2907 .6A, 40V, .6W, PNP .06
0 ohm Jumper
33K ohm ±5%, .25W
.01
.01
.01
.01
.05
.02
.31
.01
.01
.05
.04
.05
1.95
.01
.04
.04
.04
.29
.68
.04
.05
.04
.01
.01
.01
.03
.02
.01
.02
.05
.05
.01
.01
189
190
191
192
193
194
195
196
197
198
200
161
162
163
164
165
166
166
166A
167
153
154
155
156
157
158
159
160
167
168
169
170
171
172
173
174
175
176
177
178
179
CPR0050
CPR0050
CPR0144
CPR0050
CPR0009
CPR0024
180
181
182
183
183A
184
185
186
187
CPQ1308
CPR0050
CPR0351
CPC1041
CPR0050
CPR0143
CPQ1307
CPM2037
CPC1036
188 CPM2036
188A CPM2037
CPI1405
CPR0144
CPR0017
CPR0018
CPR0168
CPR0015
CPC1032
CPC1102
CPR0504
CPR0013
CPR0142
CPR0050
CPQ1303
CPR0012
CPI1410
CPR0011
CPR0393
CPS1755
CPR0011
CPR0050
CPC1039
CPC1036
CPC1032
CPR0018
CPD1252
CPC1109
CPI1401
CPR0377
CPR0050
CPC1104
CPR0391
CPC1032
CPC1000
CPR0157
C6
C6
C7
D7
EE9
DD9
BB3
CC4
PN2222A .6A, 30V, .5W, NPN
2.7K ohm ±5%, .25W
LM393 Dual Comparators
1.8K ohm ±5%, .25W
.05
.01
.31
.01
D5
D5
D5
E5
D7
C2
F3
G3
D4
E4
E4
F4
F4
G4
MM4
F3
D2
E2
E2
E2
E2
MM7
LL0
NN8
MM7
NN7
NN8
E2
E3
E3
E3
E3
E3
E3
E2
F3
F3
E3
D3
D3
D3
D3
E3
NN7
NN7
NN7
NN7
NN7
NN7
PP8
MM7
MM8
NN5
GG4
GG1
GG2
EE8
E3
E4
E3
E3
E3
F3
E4
E3
NN5
MM7
MM2
GG1
NN3
MM5
NN6
PP8
PP8
GG3
F4
E4
E4
GG1
MM2
JJ2
BB4
EE4
HH2
2SC3467F .1A, 200V, 1W, NPN
.16
0 ohm Jumper
150 ohm ±10%, .5W, CC
.33uF ±5% @ 50V
0 ohm Jumper
10.0K ohm ±1%, .25W
.01
2SC4159E 1.5A, 180V, 15W, NPN .36
Heat Sink, H. Width output
.047uF ±5% @ 50V
Heat Sink, V. Deflection out
GG1 Heat Sink (2092 Option)
KK1
KK1
HH1
GG2
390 ohm ±5%, 2W
"RC" 8 Conductor Header
1.8K ohm ±5% (Blooming adjust)
0 ohm Jumper
.1uF ±5% @ 50V
.047uF ±5% @ 50V
.01uF ±5% @ 50V
1N4005 1A, 600V, R-Diode
470uF ±20% @ 50V
LA7830 Vert. Def. Output
3.3 ohm ±5%, 1W
0 ohm Jumper
1000uF ±20% @ 35V
200 ohm ±5%, 2W
.01uF ±5% @ 50V
.04
.26
.01
62K ±5%, .25W (2092 Option) .01
LM324 Quad Op. Amp.
12.1K
Ω
±1%.25W (Pin. Adj) 1492
.31
.01
36K
Ω
±5%, .25W (Pin. Adj) 2092 .01
62K
Ω
±5%, .25W (H. Ras. Adj.) .01
8.06K
Ω
±1%.25W (Pin. Adj) 1492 .01
22K
Ω
±5%, .25W (Pin. Adj) 2092 .01
.01uF ±5% @ 50V .04
100uF ±20% @ 25V
"G" PRA (H. Width Control)
6.8K ohm ±5%, .25W
7.15K ohm ±1%, .25W
0 ohm Jumper
0 ohm Jumper
0 ohm Jumper
12.1K ohm ±1%, .25W
0 ohm Jumper
1K ohm ±5%, .25W
3.3K
Ω
±5% .25W (Max. iBeam adj.)
56pF ±5% @ 100V
127K ohm ±1%, .25W
.01
.05
.04
.04
.05
.92
.01
.01
.01
.01
.01
.01
.01
.01
.01
.01
.05
.08
.01
.11
.04
.13
.11
.01
.02
.19
.67
.03
.01
.22
.04
.04
.03
.01
26
Board No.s 201 to 300 REPLACEMENT PARTS LIST Models 1492 and 2092
CERONIX
PART No.
DESCRIPTION
CERONIX
PART No.
DESCRIPTION
240
241
242
243
244
245
246
247
232
233
234
235
236
237
238
239
248
248A
249
250
251
224
225
226
227
228
229
230
231
215
216
217
218
219
220
222
223
207
208
209
210
211
212
213
214
201
202
203
203
204
205
206
CPC1101
CPC1043
CPR0017
CPR0163
CPC1000
CPC1005
CPC1058
CPC1032
CPC1002
CPC1032
CPC1036
CPS1759
CPR0503
CPC1104
CPC1102
CPI1400
CPC1036
CPR0502
CPD1257
CPR0002
CPC1102
CPC1026
CPC1025
CPC1028
F5
G5
F5
D6
D6
F5
F5
F5
F5
F5
F5
F5
F5
E5
E5
E5
E5
E6
F5
F6
D6
D6
D6
E6
E6
E6
MM5
GG2
MM5
MM5
JJ1
JJ2
HH2
HH2
II1
NN2
JJ2
HH2
JJ6
GG3
KK3
II1
KK4
JJ2
GG3
GG3
HH4
HH4
II4
10uF ±20% @ 50V
1.0uF ±5% @ 50V
36K ohm ±5%, .25W 1492
28.0K
Ω
±1%, .25W 2092
56pF ±5% @ 100V
1000pF ±20% @ 500V
.1uF ±5% @ 50V
.01uF ±5% @ 50V
330pF ±10% @ 100V
.01uF ±5% @ 50V
.047uF ±5% @ 50V
Vertical Deflection Bias Adj.
Vertical Deflection Bias Adj.
4X .062 Dia. Bead Pins (YC)
"H" PRA Vertical Control
1000uF ±20% @ 35V
100uF ±20% @ 25V
LA7851 V. & H. Control IC
.047uF ±5% @ 50V
"I" PRA Horizontal Control
1N4742 12V ±5%, 1W, Z. DIODE
18 ohm ±5%, .25W
100uF ±20% @ 25V
1000pF ±5% @ 100V
330pF ±5% @ 100V
6800pF ±10% @ 100V
CPC1100
CPC1032
CPC1027
CPC1100
CPC1003
CPR0138
CPQ1307
CPT1505
CPS1753
CPR0426
CPS1758
CPS1758
CPRO427
CPR0425
CPRO430
CPR0366
CPD1264
CPR0002
CPQ1310
CPR0019
F2
F2
F3
F3
F1
F1
F1
F2
F6
F7
F7
E7
E6
F6
F6
F6
G1
G2
G2
G2
G2
G3
H3
LL9
GG9
LL9
HH8
KK6
JJ6
HH6
HH6
HH6
II4
JJ4
JJ4
JJ4
MM3
KK4
MM3
NN3
GG9
GG9
GG9
GG9
1uF ±20% @ 50V
.01uF ±5% @ 50V
6800pF ±5% @ 100V
1uF ±20% @ 50V
2,200pF ±20% @ 1KV
2.05K ohm ±1%, Hfo adjust.
2SC4159E 1.5A, 180V, 15W, NPN
Horizontal Drive Transformer
"PC" 2 Conductor Header
Optional AC noise capacitor.
C-200-7, 25-.5
Ω
Inrush Current Limiter
Optional AC line capacitor.
"CC" .093 Dia. Bead Pins
"CC" .093 Dia. Bead Pins
BF5ROM125 Posistor (Optional)
SS1-3A 3 AMP FUSE
Dual Posistor (Optional)
100K ohm ±5%, .5W, CF
FR205 2A, 600V, F-Diode
18 ohm ± 5%, .25W
Optional 127V line control.
2SA1371E .1A, 300V, 1W, PNP
100K ohm ±5%, .25W
.01
1.26
.22
.05
1.48
.28
.22
.01
.04
.68
.05
.01
.05
.06
.06
.03
.04
.04
.06
.04
.03
.01
.36
.60
.21
.04
.17
.01
.01
.03
.03
.05
.04
.03
.04
.04
.02
.02
.96
.25
.01
.04
.01
283
284
285
286
287
288
289
290
275
276
277
278
279
280
281
282
291
292
293
294
295
296
297
298
298
300
267
268
269
270
271
272
273
274
259
260
261
262
263
264
265
266
252
252A
253
254
254A
254B
255
256
257
258
CPI1403
CPC1032
CPC1003
CPD1252
CPQ1302
CPC1039
CPC1102
CPR0169
CPC1002
CPR0050
CPD1251
CPC1026
CPR0376
CPD1264
CPC1037
CPD1256
CPC1034
CPT1500
CPR0356
CPR0353
CPC1035
CPD1264
CPC1003
CPD1264
CPD1264
CPC1003
CPR0050
CPD1264
CPC1105
CPC1105
CPT1503
CPR0050
CPD1264
CPC1039
CPC1039
CPD1264
CPR0351
CPC1006
CPD1264
CPM2027
CPQ1304
CPR0050
CPR0002
CPR0147
CPR0501
CPR0011
CPC1028
CPC1000
CPC1000
CPC1027
CPR0050
GG8
GG7
GG8
GG9
GG7
GG9
HH8
HH8
KK6
J3
I2
I3
I3
KK8
KK7
G3
G3
G3
G3
H3
H3
H3
H3
G4
G4
G3
H4
J3
J3
J3
I4
I5
G5
G5
G5
I3
H3
I3
I4
G3
I4
I3
I3
LL7
KK7
KK9
MM4
II5
II5
JJ6
PP3
PP6
PP6
PP6
II6-8
HH6
JJ9
KK8
KK9
JJ7
HH9
KK7
II8
RR4
HH7
HH7
II7
HH7
HH8
PP8
HH8
KK5
KK6
JJ6
JJ5
KK9
KK8
KK6
LL8
KK8
G2
H2
H2
H1
H2
J1
I1
J1
H1
H1
H1
H2
J2
J2
J2
I2
I2
I2
J3
J3
FR205 2A, 600V, F-Diode
2,200pF ±20% @ 1KV
FR205 (220V Option)
FR205 2A, 600V, F-Diode
2,200pF ±20% @ 1KV
0 ohm Jumper
FR205 (220V Option)
150uF ±20% @ 250V
150uF ±20% @ 250V
Switch Mode Transformer
0 ohm Jumper
FR205 2A, 600V, F-Diode
.1uF ±5% @ 50V
.1uF ±5% @ 50V
FR205 2A, 600V, F-Diode
150 ohm ±10%, .5W, CC
200pF ±10% @ 1KV, NPO
FR205 2A, 600V, F-Diode
HEAT SINK , Power Supply
2SK1446LS 450V, 7A, MOS FET
0
Ω
Jumper, to ground PS H. S. 267
18 ohm ±5%, .25W
1.0 Meg ohm ±1%, .25W
"J" Power Supply PRA
1.8K ±5%, 127V line adjust.
6800pF ±10% @ 100V
56pF ±5% @ 100V
56pF ±5% @ 100V
6800pF ±5% @ 100V
0 ohm Jumper
Power Supply Fo Adjustment.
XRC5184 Custom P. S. IC
.01uF ±5% @ 50V
2200pF ±20% @ 1KV
1N4005 1A, 600V, R-Diode
MPSA64 .3A, 30V, D-PNP
.1uF ±5% @ 50V
100uF ±20% @ 25V
191K ohm ±1%, .25W
330pF ±10% @ 100V
0 ohm Jumper
1N4148 10mA, 75V, Diode
1000pF ±5% @ 100V
1.2 ohm ±5%, 1W
FR205 2A, 600V, F-Diode
.1uF ±10% @ 250V
TZ160B-T3 160V ±5%, 1W, Z-Diode
.022uF ±5% @ 630V
Flyback Transformer
2.2K
Ω
±10%, .5W, CC 1492
1K
Ω
±10%, .5W, CC 2092
3,300pF ±5% @ 200V
.01
.06
.03
.04
.07
.18
.08
10.64
.07
.07
.06
1.91
.04
.03
.04
.08
.05
.05
.01
.03
.01
.04
.03
.04
.04
.03
.01
.04
.88
.88
2.10
.01
.04
.05
.05
.04
.01
.01
.68
.01
.03
.03
.03
.06
.01
.07
.04
.04
.08
.94
.01
27
Board No.s 301 to 490 REPLACEMENT PARTS LIST Models 1492 and 2092
CERONIX
PART No.
DESCRIPTION
420
421
422
423
424
425
426
413
414
415
416
417
418
419
406
407
408
409
410
411
412
401
402
403
404
405
405
307
308
309
310
311
312
313
314
301 CPT1523
301 CPT1506
302
303
304
305
CPT1506
CPR0392
CPQ1305
CPC1050
305 CPC1059
306 CPC1030
306 CPC1055
315
316
317
CPC1034
CPD1252
CPR0365
CPD1252
CPD1253
CPD1264
CPR0050
CPC1044
CPT1504
CPC1105
I6
I6
J6
J6
H6
H7
I6
H7
G7
H6
H6
H6
G5
G5
G6
F7
PP7 220uH Horz. Width Coil. 1492
PP7 Horz. Linearity Coil 2092
PP6 Horz. Linearity Coil
NN4 270 ohm ±5%, 2W
NN3 2SD1651 5A, 1.5KV, NPN
RR7 .47uF ±5% @ 250V 1492
RR7 .33uF ±5% @ 250V 2092
RR6 .01uF ±3% @ 1.6KV 1492
RR6 8,200pF ±3% @ 1.6KV 2092
RR8 .022uF ±5% @ 630V
RR6 1N4005 1A, 600V, R-Diode
NN4 470 ohm ±5%, .5W, CF
RR7 1N4005 1A, 600V, R-Diode
RR8 1N4937 1A, 600V, F-Diode
NN4 FR205 2A, 600V, F-Diode
0 ohm Jumper
I6
I7
J7
PP8 2.7uF ±10% @ 100V
PP7 Horizontal Width Coil
II5 150uF ±20% @ 250V
TUBE SOCKET BOARD
CPS1750
CPR0350
CPR0352
CPR0353
CPR0375
CPR0050
CPR0353
CPD1250
CPD1250
CRT SOCKET
NN1 47 ohm ±10%, .5W, CC
NN1 470 ohm ±10%, .5W, CC
NN0 1K ohm ±10%, .5W, CC
PP1 .68 ohm ±5%, 1W 1492
PP1 0
Ω
Jumper 2092
NN1 1K ohm ±10%, .5W, CC
MM0 FDH400 .1A, 200V, Diode
MM0 FDH400 .1A, 200V, Diode
427
CPD1250
CPR0353
CPR0353
CPC1040
CPR0355
CPR0019
CPQ1306
CPR0353
CPR0029
CPC1003
CPR0353
CPC1002
CPR0350
CPR0354
CPS1769
CPS1768
CPS1758
MM0 FDH400 .1A, 200V, Diode
NN0 1K ohm ±10%, .5W, CC
PP1 1K ohm ±10%, .5W, CC
MM1 .015uF ±10% @ 250V
NN1 100K ohm ±10%, .5W, CC
MM1 100K ohm ±5%, .25W, CF
MM1 2SC3675 .1A, 1.5KV, NPN
PP1 1K ohm ±10%, .5W, CC
MM1 200K ohm ±10%, .25W, CF
PP1 2200pF ±20% @ 1KV
PP1 1K ohm ±10%, .5W, CC
PP1 330pF ±10% @ 100V
NN1 47 ohm ±10%, .5W, CC
NN1 10K ohm ±10%, .5W, CC
10 Conductor Cable
10 Conductor Cable, Double length.
.093 Dia. Bead Pin
.08
.02
.01
.02
.03
.04
.01
.60
.60
.60
.04
1.48
.36
.38
.26
.37
.32
.63
.88
.03
.07
.07
.07
.07
.01
.67
.07
.07
.07
.83
.99
.02
.01
.03
.07
.03
1.54
.07
.07
.07
.03
.01
.07
.03
.03
CERONIX
PART No.
DESCRIPTION
REMOTE CONTROL BOARD
485
486
487
CPA4102
CPR0400
483
481
CPR0401
CPR0402
484 CPR0403
482 CPR0405
CPR0007
CPS1767
Remote PCB Assembly.
FF2 1K ohm White Pot
FF2 1K ohm Blue Pot
FF1 10K ohm Yellow Pot
FF2 20K ohm Orange Pot
FF1 500 ohm Black Pot
FF1 750 ohm ±5%, .25W
"RC" 8 Conductor Cable
4.75
.17
.17
.17
.17
.17
.01
.87
PCB ASSEMBLIES
CPA4100
CPA4103
CPA4101
1492 Main PCB Assembly
2092 Main PCB Assembly
CRT P.C. Board Assembly
105.00
115.00
7.50
28
29
1
2
3
4
5
6
7
A B C D E F G H I J
GND
GND
GND
VIDEO INPUT CONN.
VC
006
340R, 031
3.92K, 003
8 7 6 5 4 3 2 1
340R,038
270R, 045
1.8K, 046
1.8K, 047 1 2 3 4 5 6
H
S
V
S
R G B
270R, 048
1K, 050
4.42K, 051
2.7K, 052
2907
053
909R, 054
1.62K, 055
205R, 056
412R, 057
1K, 058
.015uF, 82B
9
C5346
12
036
14 16
15.8K, 033
12.1K, 034
340R, 035
1 2 3 4 5 6 7 8 11 13
4 3
2222
063
.1uF, 69
750R, 064
A64
065
067
5 6
2 1
072
LM393
7
+
8
10uF
068
073
074
075
6.8K, 080
076
1.8K, 077
1K, 078
"B" PRA
.1uF, 84B
604R, 044
18
158
2 3 4 5 6 7 8
RC
REMOTE C.
81B
1nF, 88B
H400, 90B
0
Ω
, 160
+
10uF
066
62K, 070
270R, 071
7 6
8
165
9
5
100uF
+
169
.1uF, 161
.01uF, 163 none, 62K, 164
4 3 2 1
LM324
12
1 2 3 4 5 6 7
12K, 36K, 166
8.1K, 22K, 167
8 9
"G" PRA
14
62K, 166A
14
10nF, 168
16
170
3467
83B
0
Ω
, 85B
2.7K, 094
.1uF, 095 .1uF, 096
510R, 89B
1370
87B
4148, 86B
1370
91B
1.8K, 92B
7.15K, 172
6.8K, 171
1 2 3 4 5 6 7 8
.015uF, 82G
3467
83G
1.62K, 097
A64
098
0
Ω
, 85G
1.21K, 100
1 2 3 4 5 6 7 8 11
.015uF, 82R
3467
83R
2907
139
7812, 130
4148, 102
4005, 101
11
GND
0
Ω
, 85R
11
6.8K, 107
2222
104
4148, 106
4148, 105
4005,103
1 2 3 4 5 6 7 8 9
12
123
14
9 8 7 6 5 4
CA3224
3 2 1
+
10uF
125
16
1,000uF
131
18
+
10uF
126
+16V
20
13
"B" PRA
+
10uF
127
22
18
81G
.1uF, 84G
510R, 89G
1370
87G
4148, 86G
13
"B" PRA
.1uF, 84R
510R, 89R
1370
87R
4148, 86R
"C" PRA
18
81R
14 16
H400,90G
1370
91G
1.8K, 92G
H400, 90R
1nF, 88R
1370
91R
115
1nF, 88G
1.8K, 92R
20
GND
TC
2
3
4
5
8
9
6
7
10
114
1K, 112
+24V
200R
+24V
0
7 6 5 4 3 2
LM324
1
8
146
9 12 14
22K, 147
22K, 148
33K, 143
33K, 142
33K, 141
Ω
, 140
.1uF,150
33K, 152
2222
153
2.7K, 154
0
Ω
,151
6.8K, 138
1.8K, 137
6.8K, 136
1.8K, 135
4148, 134
1.8K, 133
8 7 6 5
LM393
155
1 2 3 4
1,000uF
1.8K, 156
215
390R
196
47nF,187
56pF, 198
157
1
2 3 4 5 6
7 8
9
+
100uF
216
1 2 3
+
100uF
225
188
6 7 8
9
1
3467
180
20
1.0uF, 202
1 2 3 4 5 6 7 8 9
HORIZONTAL
DRIVE XFR.
CPT1505
4
+
10uF
201
18
LA7851
470uF
3
191
7
LA7830
6 5 4
192
3 2
"I" PRA
+
1uF
230
237
2
14
*
241
20
G
2SC4159, 236
AC POWER
PC
238
CC
C-200,240
5ROM
2SC4159
185
56pF, 204
330pF, 208
1nF, 205
.1uF, 206
10nF, 207
"H" PRA
16 14
218
14
C
E
B
1
12
47nF, 210
16
16
214
222
+
1uF
233
H. HOLD
SEL. RES.
2.05K, 235
211
212
20
H
I
20
242
243
244
3 AMP
FUSE
245
10nF, 209
Vo Vr
H. WIDTH
COIL, 1492
CPT1523
LINEARITY
COIL, 2092
CPT1506
301
LINEARITY
COIL
CPT1506
302
270R
303
186
1,000uF
195
Hr
*
246
Optional Dual
Posistor.
100K, 247
FR205,248
18
Ω
, 248A
1371
250
100K, 251
1 2 3 4 5 6 7 8 9
YC
213
6.8nF,274
*
249
Ho
2.2K
2SD1651, 304
298
253
220 VAC
Input
"J" PRA
10nF, 281
2.2nF, 282
56pF, 275
56pF, 276
279
6.8nF, 277
3.3nF
300
.47uF for 1492
.33uF for 2092
305
.01uF for 1492
8.2nF for 2092
7
8
1
2
5
6
3
4
16
15
14
C5184
13
12
280
11
10
9
.022uF
307
306
470R, 309
+
150uF
250V
256
+
150uF
250V
257
14 16
.1uF,285
A64
284
+
100uF
286
1
10
SWITCH MODE
TRANSFORMER
150R, 264
200pF, 265
FR205,266
18R, 270
1.00M, 271
272
330pF,288
2
FLYBACK
TRANSFORMER
9
4005, 308
2.7uF
H. Width Coil
3
297
8
20
4
7
4005, 310
4937, 311
CPT1504
316
315
1.2
Ω
292
22nF
296
5
6
G
D
S
+
258
.1uF, 262
FR205,263
2SK1446
FR205 , 312
0 ohm, 313
150uF @ 250V
268
317
267
0
Ω
, 269
FR205,293
+127V
.1uF, 294
TZ160B, 295
160V
ZENER
GND
1
2
3
4
5
6
7
30
Block Diagram Review
GAME
VIDEO
SYNC
3
VIDEO
Interface
A
3
F.B.P.
V retrace
Beam limit
M. gain
H
SYNC
Interface
I
2
BLANKING
VIDEO
AMPS.
Bias
B
3
Beam
Current
Feedback
C
3
3
3
AUTO BIAS
IC
H. blank
V. blank
Auto
Bright
F
3
D
Beam current buffer
Program pulse
Grid pulse
E
3
CRT
G
V
DY
H
DY
ISOLATION
Transformer
(IN GAME)
V s
VERTICAL
CONTROL
I. V. Feedback
J
VERTICAL
OUTPUT
High Efficiency
L
VERTICAL
AUTO BIAS
K
EHT
H s
H. Pos.
HORIZONTAL
CONTROL
Sync delay
M
V. Size &
V. Ras. Pos.
REMOTE
CONTROLS
(PCB)
Q
H.
Driver
N
H.
Output
O
FBT
PINCUSHION
2
HORIZONTAL
Size Control
R
DIODE
Modulator
Beam Current
S
P
+127V
VOLTAGE
DOUBLER
Raw DC
320V
T
V-
LOAD
(VIDEO & DEFLECTION)
V
-200V
SWITCHING
REGULATOR
Sync
U
+16V
+27V
+12V
Zener
X
Deflection
Supply
OVER
VOLTAGE
PROTECT
Y
+12V
Regulator
W
Video
Supply
31
AUTO BIAS AND AUTO BRIGHT CIRCUIT, FUNCTION, DESCRIPTION
The auto bias circuit is a control system that forms a closed loop for controlling the CRT bias voltage. It generates a set of conditions where the current near the cutoff voltage of each gun is measured, and then adjusts the bias voltage of the video amplifiers, to set the correct black level voltage for each gun. This color balance adjustment is necessary, since each gun in the color picture tube can have a different cutoff voltage, which also, will change as the CRT ages.
If the picture tube gain changes, the auto bias circuit would adjust all three guns in the same direction to maintain constant black level. This effect reduces the auto bias voltage range which is needed for the cathode differential voltage adjustment. To prevent this occurrence a second control loop is added to the system. This second control loop is called the auto bright circuit and corrects for CRT gain changes. The auto bright circuit senses any common bias voltage change and controls the screen grid (G2) to hold the common bias voltage constant.
SIMPLIFIED PICTURE TUBE VIDEO BIAS CONTROL CIRCUIT: (One channel shown)
VIDEO
INTERFACE
+
Video
Amp.
CA3224E
R
G
B
CRT
Beam
Current
Buffer 5K
.1uF
122
123
Red input
SW normal
A
B
C
Red hold cap.
10uF
+
127
4.2V
Auto Bright
Amplifier
+
LM324
8
*
G1 G2
FBT
Screen adj.
LM324
+ comp.
R
33K
4.2V
200
Ω
C8
.047uF
V ref.
G
33K 22K
GREEN CHANNEL
100K
B
33K
68.1K
BLUE CHANNEL
2.7K
+10V
V sync
H sync
Grid pulse
Counter, Decoder
Control Logic
Program
Pulse
*
Adjust, FBT bottom pot, for 4.6V at pin 8.
Note; All XX92 boards have a solder connection on;
C thick films, with a solder connection in the middle.
The auto bias circuit performs all of its sensing and bias corrections during the sixteenth to the twenty first horizontal cycle, after the vertical blanking has started. Before the sixteenth cycle, the SW in the auto bias IC is open ( SW in "C" position).
During the 16,17, and 18 horizontal cycle, the CRT is brought out of cutoff by the grid pulse. The resulting beam current produces a voltage at the beam current buffer output.
This voltage is applied to the coupling capacitor
122
. At the other side of the coupling capacitor is the channel input, which is clamped to V ref. (SW in "A" position). The voltage amplitude of the amplifier output with the cathode current information is then stored in the coupling capacitor
122
during this time.
During the next three horizontal cycles (19, 20, and 21), the SW is switched to pass current to capacitor
127
which is the bias voltage storage capacitor. At the same time a program pulse is applied to resistor
C8
which, if the bias was correct during the previous cycle, exactly balances the voltage stored in the coupling capacitor and no difference is sensed at the channel input. The channel amplifier, in this case, does not output current and the voltage of capacitor
127
stays unchanged.
If the CRT cathode is too far into cutoff, less beam current flows, the beam current buffer puts out a smaller negative pulse, less voltage is stored in the coupling capacitor, the program pulse amplitude (which is constant) is now larger than the stored (beam current) voltage and the channel amplifier will add current to the bias voltage, storage capacitor
127
, correcting the low bias voltage which caused the cathode to be too far into cutoff.
After the program pulse is over, the SW is switched to the open position again and the next time the bias voltage can be adjusted is during the next vertical blank time.
32
AUTO BIAS AND AUTO BRIGHT CIRCUIT DESCRIPTION
The beam current feedback circuit uses a PNP video transistor
91R
to direct most of the beam current to the auto bias circuit while passing the voltage waveform, from the video amplifiers to the CRT cathodes. Diode
90R
and capacitor
88R
insure that no video waveform distortion occurs. An additional benefit of this circuit is that it protects the video amplifiers from the destructive arc energy. Resistors
92R
and
93R
divide energy due to CRT arcing, between the video amplifier transistors and the beam current feedback transistor
91R
. The beam current is filtered by capacitor
108
and resistor
C10
and is buffered by an operational amplifier, which translates the beam current into a low impedance voltage. This voltage is applied to a coupling capacitor
122
through a
200 ohm resistor
C8
. The 200 ohm and the 68.1K resistor
C3
forms the program value which sets the black level voltage via the action of the program pulse.
Capacitor
121
is used to stabilize the transconductance amplifier which is used at the channel input of the auto bias IC
123
. The auto bias IC stores the bias voltage of this channel in capacitor
127
at pin 21. This voltage is buffered by an internal amplifier, with output at pin 20, which is connected to the Red video amplifier bias input.
Resistor
141
,
142
, and
143
are part of the auto bright circuit. They are used to sum the bias voltage of each of the three channels via a voltage node at the auto bright amplifier,
146
pin 9. The resulting output voltage then controls the screen grid via transistor
417
. Resistors
413
and
418
protect the CRT from excessive current during arcing. Capacitor
423
supplies a low AC impedance to GND to insure that the CRT gain is constant during each horizontal line.
Resistor
420
defines the current gain of, and stabilizes, the auto bright control loop.
Resistor
148
and capacitor
150
act as a low pass filter to reduce the chance of damaging the amplifier
146
due to CRT arcing. Resistors
415
, and
416
protect the auto bright control transistor
417
. The grid pulse is generated by a discrete transistor
153
to protect the auto bias IC from possible arc energy.
Pullup resistor
154
supplies the grid pulse voltage during the grid pulse time.
The auto bias IC (CA3224E) is designed for a supply voltage of +10V and since the video amplifier requires +12V, three diodes
101
,
103
, and
145
are used to supply this IC. Resistors
C4
and
C7
form a voltage divider which supplies the bias voltage to the LM324
146
. The green and blue channel circuits are identical to the red channel and are controlled by the timing logic in the same way. Refer to the waveforms at the bottom left of page 34 for the timing relationship. The vertical retrace pulse, from the LA7851, starts the 21 count auto bias state counter. The grid pulse becomes active between the 15 and 18 horizontal cycle and the program pulse is active between the 18 and 21 horizontal cycle. These two pulses in conjunction with the internal control of the transconductance amplifier output switch are what measure and set the video bias.
33
10K
425
VIDEO
INTERFACE
1K
330pF
421
422
+
Video
Amp.
AUTO BIAS AND AUTO BRIGHT SCHEMATIC
1000pF
88R
FDH400
90R
2SA1370
2.2K
92R
+4.2V
10
9
AUTO BRIGHT CIRCUIT
2SC3675
+
1/4
LM324
8
22K 100K
148 416
146
.1uF
417
100K
22K
150
420
R
G
B
100K
415
91R 147
Red BEAM CURRENT
2.2K
93R
Red video BIAS control line.
1K
418
G1
1K
413
CRT
G2
4,700pF
423
Green, Blue
Video BIAS
LINES
Green &
Blue BEAM
CURRENT
18
14
15
10
To CRT Grid #1
+12V Video Supply
1N4001 1N4001
1N4001
+10V
101 103 145
2.74K
C7
11
1.82K
C4
4K
C10
6,800pF
108
4K
C11
6,800pF
110
4K
C14
6,800pF
111
V. Retrace
V. Blanking
H. Blanking
Bias active
Grid pulse
Program pulse
8.0-9.0VDC
8.4V 17mS
1
+10V
2.7K
154
5
6
146
+
1/4
LM324
7
12
13
3
2
16
13
19
C9
+
1/4
LM324
GND
5K
5K
C12
12
+
1/4
LM324
5K
C15
PN2222
14
20
200
Ω
C8
68.1K
C3
200
Ω
C13
68.1K
C2
200
Ω
C16
68.1K
C1
Grid pulse
.5-.8VDC
.7V
17mS
153
1
17
V. RETRACE
18
GND
H
7
5
4
1
B
AUTO BIAS CIRCUIT
.1uF
144
.1uF
122
1
2
5.8-
6.4V
AUTO BIAS IC
GND
CA3224E
Vcc
123
Red input
Red hold cap.
sw.
normal comp.
22
21
10uF
+
20
127
2.5-
6.7V
.047uF
121
3
1.2-
2.5V
33K
141
.1uF
120
4
5.8-
6.4V
.047uF
118
5
1.2-
2.5V
.1uF
117
.047uF
116
33K
152
8
20K
C5
2,9 sw. in grid pls. pos.
Green input Green hold cap.
sw.
19
18 comp.
10uF
+
126
2.5-
6.7V
33K
142
6
5.8-
6.4V
Blue input Blue hold cap.
17 sw.
7
1.2-
2.5V
comp.
16
.1-
.3V
8
9
10
6.3-
7.7V
11
6V REF.
CL
START
COUNTER
FF Q
GND
BIAS
15
14
5V REF
EN
21 H. LINE
COUNTER
CL
DECODER sw. control
GRID
PULSE
AUTO
BIAS
ACTIVE
PULSE
13
PROGRAM
12
10uF
+
125
2.5-
6.7V
4.6-5.2VDC
33K
143
To vertical blanking
1.9-2.3VDC
4V 17mS
34
VERTICAL AND HORIZONTAL SYNC CIRCUIT DESCRIPTION
The 1492 Monitor has a separate input for horizontal and vertical sync. The horizontal sync pulse is normally positive going. The horizontal deflection control circuit will sync on the rising edge of this pulse. If horizontal sync is negative going, the picture is shifted to the left, and may be out of range of the horizontal picture position adjustment circuit.
To sync on the falling edge of horizontal sync, a solder bridge is installed on the I PRA.
The vertical deflection circuit will sync on either a negative or positive sync pulse, provided that the pulse width is between two and twenty horizontal cycles long. Both the vertical and horizontal sync lines are joined for composite sync operation.
VERTICAL AND HORIZONTAL SYNC CIRCUIT
VIDEO +12V
DEFLECTION +12V
1K
1.8K
46
GND
1.8K
270
Ω
45
270
Ω
48
22K
62
3
2
+
8
1/2
LM393
67
5
+
1/2
LM393
6
4
1
7
78
6.8K
80
12K
176
1.8K
77
56pF
198
10uF
+
68
1.8K
I 1
12K
I 2
8.8K
22K
I 12 I 3
1
19
Horizontal
Sync input
LA7851
Deflection
Control IC
Vertical
Sync input
47
.14-.16V
270
Ω
61
.047uF
187
GND
HORIZONTAL
SYNC
H s
V s
VC
1
VC
2
VERTICAL
SYNC
This sync interface incorporates a dual voltage comparator
67
and a resistive input circuit for high reliability. For TTL level sync signals, the resistive inputs are seven to one attenuators comprised of resistors
45
,
46
,
47
, and
48
. The comparators are biased to .15 volts by resistors
61
,
62
which permit direct connection to an RS170 sync source by removing resistors
45
and
48
.
The horizontal sync signal from the comparator output is pulled up by resistor
80
and attenuated by resistor
176
and
I1
, for correct drive amplitude. It is differentiated by capacitor
198
and applied to the horizontal sync input, pin 1, of the LA7851.
Bias resistors
I2
and
I3
set up the correct voltage for positive edge triggering.
By adding resistor
I12
, the LA7851 is programmed for negative edge triggering.
This is used when the horizontal sync pulses are negative going. Resistor
I12
is connected by adding a solder bridge to the I PRA solder pads above pin 6.
The vertical sync signal from the second comparator is coupled to the LA7851, vertical sync input, via a coupling capacitor
68
. Resistor
77
and capacitor
187
form a low pass filter to eliminate false triggering by horizontal sync pulses in the case of composite sync.
Resistor
78
and capacitor
77
compliments the comparator open collector output by acting as a pullup. These resistors also form a voltage divider which insures that the capacitor
68
is not reverse biased and provide the proper vertical sync drive amplitude.
The LA7851 vertical sync input circuit is designed to accept either positive or negative sync pulses, but will not work with a sync signal that is close to a square wave.
35
VERTICAL DEFLECTION CIRCUIT, FUNCTION, DESCRIPTION
The LA7851 IC and the H PRA have all the active components to control the vertical deflection.
LA7830 is a high efficiency vertical yolk driver IC. Together they form a compact and efficient vertical deflection system.
+12V
.1uF
18 V.
OSC
.047uF
V. Auto Bias on H PRA
22K 22K 200K
118K
.01uF
22K
17
+12V
+
10uF
76.8K
H6
301
Ω
1uF
202
16
S Q
FF
R Q
5V
COMP.
V
SYNC
19
+ or -
VERT.
SYNC
LA7851
218
3.4V
AMP.
15
VERT. YOLK
+ 1000uF
220uF
+
330
Ω
330
Ω
+24V LINE
7
3
CONTROL
V
SIZE
500
Ω
3.3
Ω
193
6
RETRACE
BOOSTER
LA7830
192
OUTPUT
2
4
The vertical oscillator supplies the start time for the vertical cycle and when vertical sync is present, sync supplies the start time to the vertical oscillator. The linear vertical ramp current which is necessary for linear vertical deflection is generated by supplying a capacitor
202
with a constant current from resistor
H6
, at a voltage node (pin 16).
The voltage at this node is held constant by a system of amplifiers which drive the deflection yoke. The yoke current sensing resistor
193
is connected to the other side of this capacitor
202
and supplies the ramp voltage which balances the current from
H6
during trace time.
To generate the other half of the deflection yoke sawtooth current (vertical retrace), a flip flop is set by the vertical oscillator which partly discharges the capacitor
202 and causes the drive voltage across the yoke to reverse. The amount of discharge of capacitor
202
determines the vertical output voltage for the next cycle and is controlled by a timer at pin 17. The time out of the timer is controlled by the vertical output voltage from two different paths. One path is through the 34K and 118K resistors which supplies the higher frequency component for the timer and stabilize the vertical amplifier. The other path is through the vertical auto bias circuit which detects the minimum vertical output voltage over many vertical cycles and supplies a second current source to the timer. This second current source has a wide dynamic range and will hold the vertical output voltage well within operating limits for both 50Hz and 60Hz with no need for manual adjustment.
To better understand the LA7851 bias control loop, imagine the vertical output voltage goes up, the time out shortens which causes the capacitor
202
to be less discharged. This raises the voltage on capacitor
202
and lowers the vertical output voltage. This type of vertical bias control system has the advantage of only correcting the bias during retrace which means that it will not cause current ramp distortion during vertical trace time.
The vertical yoke driver LA7830 is the power output stage for the vertical amplifier.
It has a built-in voltage booster circuit to reduce vertical retrace time without the power losses associated with a high vertical supply voltage.
36
VERTICAL DEFLECTION CIRCUIT DESCRIPTION
LA7830
Remote Control PCB
HEAT
SINK
188
VERTICAL
GND
192
POWER
AMPLIFIER
VERTICAL
0 VDC
2-4V 17mS
VERTICAL
SIZE
500
Ω
482
750
Ω
RC8
RC6
0
Ω
181
0
Ω
1
330
Ω
330
Ω
20
1
18
1K
H12
+12V
88K
H20
200K
22K
H15
22K
H16
VERTICAL
RASTER
POSITION
1K
483
486
DEFLECTION +12V SUPPLY
174
8
H1
1uF
10
H2
301
Ω
11
1N4148
H25
3904
H13
3906
H22
RC3
VIDEO +12V SUPPLY
VERTICAL SYNC Vs
The vertical sync, input circuit (LA7851 pin 19), is coupled to the sync interface circuit with a 10uF capacitor
6 8
. The oscillator cycle is terminated if the voltage at pin 19 goes up or down more than one volt from its DC bias voltage, which enables synchronizing on positive or negative sync pulses.
For composite sync, capacitor
187
limits the P-P horizontal component to less than .4 volts.
202
H5
3.3
Ω
10uF
H24
H23
22K
H14
.01uF
207
GND 15
193
+12V
GND
V. RTN.
+12V
GND
216
10uF
068
100uF
GND
0
Ω
175
.047uF
.1uF
206
VERT.
OSC.
5.7-6.6VDC
4V 17mS
187
Hp5,2
5.8-6.5VDC
4V 17mS or
20
VERTICAL
V+
19
VERTICAL
± SYNC INPUT
127K
200
4
22K
H17
7
18
84K
C
H3
+5Hz
VERTICAL
OSCILLATOR
The charge current to (the vertical oscillator capacitor)
206
comes from +12V through a combination of five resistors. This resistor network is made up of
200
,
H17
,
H3
,
H18
, and
H19
.
[Solder connection B decreases Vfo by 6Hz and connection C increases Vfo by 5Hz. See page 56 for the location of the solder connections on the H PRA. This adjustment is only used if Vfo is outside the range of 39Hz to 48Hz. The normal vertical sync, frequency range, of the LA7851 is 44Hz (Vfo) to 70Hz.
] Upon vertical sync, or when the oscillator waveform reaches 6 volts, the capacitor
2 06
is rapidly discharged by a transistor and a resistor, inside the LA7851, to 2 volts at which time the cycle starts over. Note the voltage and waveform block above pin 18.
During the discharge time of
206
the retrace and bias one shot (O/S) is triggered. This O/S consists of the flip flop and comparator mentioned in the function description. The time duration of the O/S is set by capacitor
207
and two low pass filters which are connected to the vertical output.
The higher frequency filter is made up of resistors
H10
,
H4
and capacitor
2 20
. The lower frequency filter is the Vertical Auto Bias circuit.
The V. Auto Bias senses the lowest point of the vertical output waveform with resistors
H12
,
H13
And diode
H25
. This voltage Stored by
H24
is converted to a current by transistor
H23
and resistors
H14
&
H20
. This current is reflected from the +12V line via resistors
H15
,
H16
and transistor
H22
.
This current then adds to the charging current of the bias O/S capacitor
207
. The retrace and bias
O/S outputs a low pulse, which is conducted by a diode to pin 16 and discharges capacitor
202 through resistor
H5
which causes the system to retrace. The pulse duration determines the extent of the
2 02
discharge which has to be made up by resistor
H6
during trace time. This balance between the
2 02
charge during trace time and discharge during retrace is what keeps the vertical output waveform at the proper DC level.
Pin 16 is the minus input of the vertical amplifier that extends to the LA7830 for its output stage. The other input of the vertical amplifier is tied to V ref. (3.5V).
37 t t o t r
T
VERTICAL DEFLECTION SCHEMATIC
OUTPUT
Vo
Retrace
Booster
2
18
34K
H10
17
3
VERTICAL DRIVE
INPUT
COMP.
22-25VDC
25V 17mS
4
.7-1.0VDC
.9V
17mS
5
6
RETRACE
BOOSTER
22-25VDC
1V 16mS
7
1.2VDC
25V 17mS
+
H4
9
.068uF
220
V. RTN.
+12V
GND
500K
H19
-6Hz
200K
H18
B
.16-.23VDC
5V 17mS
14,6
330pF
208
Vo
12.4 TO 14V
42V 17mS
76.8K
11
H6
3.0-3.8VDC
3V 17mS
V. BOOST
V. OUTPUT
.047uF
210
13
330
Ω
H7
12
.7-1.2VDC
.9V
17mS
17
RETRACE &
BIAS O/S
16
V Ref.
15 14
GND
LA7851
218 e f s t
Vertical size is dependent on
H6
,
202
,
193
,
H1
,
H2
, and
482
. The vertical yoke current is converted to a voltage across resistor
193
and applied to the ramp generating capacitor
202
through resistor
H1
and
H2
.
The ramp waveform on the
H1
side of the capacitor
202
is constant for any vertical size because of the constant current from resistors
H6
. For minimum vertical size, the feedback voltage is present on both resistors
H1
and
H2
. For maximum vertical size
H1
is grounded and twice the amplitude across the current feedback resistor
1 93
is required to generate the ramp waveform.
Retrace is started by partly discharging the ramp capacitor
202
through resistor
H5
.
The vertical amplifier responds to the discharge of cap.
202
by outputting a high voltage across the yoke which reverses the yoke current. When the yoke current reaches the new value dictated by the voltage on
202
, the vertical cycle starts over.
56pF
204
+27V
1N4005
190
+
220uF,35V
191
+27 V LINE
YC1
VERTICAL
YOKE
18
1,000pF
205
11.5-12.5V
1N4742
223
220
Ω
, 2W
196
1,000uF,35V
+
195
2SC3467
V
RAS. POS.
0 TO 7 VDC
19
GND
1K
H11
180
.01uF
209
YC2
150
Ω
, 1/2W
182
433
The vertical amplifier consists of a differential amplifier in the LA7851 with the
+ input at pin 16 and the - input is connected to an internal reference voltage (3.5V).
The output of this amplifier is connected to the power driver stage which is located in the
LA7830. Resistors
H7
,
H11
and capacitors
208
,
209
, &
2 10
stabilize the LA7830 during trace time and capacitors
2 04
and
2 05
provide stabilization during retrace. The retrace booster doubles the 27 volt line voltage during retrace by connecting pin 7 of the LA7830 to the
27 volt line. This raises capacitor
1 91
27 volts which then applies 54 volts to pin 3 of the
LA7830. Pin 3 is the retrace booster input and is connected to the vertical output stage. After the retrace cycle is over, capacitor
191
is recharged through diode
190
.
The vertical raster position control
483
sets the NPN transistor
1 80
base voltage. The emitter resistor
1 82
supplies current to the yoke through transistor
180
. The magnitude of this DC current directly effects the vertical raster position.
The yoke return blocking capacitor
195 provides a voltage such that the vertical amplifier can drive the yoke with a + and a - current.
38
HORIZONTAL DEFLECTION CIRCUIT DESCRIPTION
+12V
+
REMOTE
CONTROL
PCB
18
Ω
224
100uF
216
1N4742
223
100uF
+
225
HORIZONTAL
POSITION
20K
RC7
484
GND
Hs
FROM SYNC
INTERFACE
0
Ω
173
56pF
1.8K
198
I 1
7.2-8.1VDC
5V 63uS
Horizontal
SYNC INPUT
2
2.7K
I 4
8
1
12K
I 2
22K
I 3
7
+12V
Reverse
Hs
D
8.8K
I 12
GND
PICTURE
POSITION
O/S
2
7.9-8.5VDC
4.4V 63uS
DELAYED
SYNC O/S
3
8.2-9VDC
4.4V
63uS
TR.
SAW TOOTH
GENERATOR
4
.1-.3VDC
1.4V
63uS
5
3.6-4.1VDC
1.6V 63uS
218
LA7851
MULTIPLIER
BIAS
6
0V
1,000 pF
226
9
25K
I 5
6,10
330pF
227
1
11
6.8K
I13
45K
I6
160
Ω
, 2W
196
4.75K
H8
6800pF
228
+
230
1uF
+
18
1uF
233
10K
I 7
The horizontal control circuit's functions are:
1. To provide the horizontal output circuit
with a stable frequency with or without
incoming horizontal sync.
2. To be able to adjust the picture position,
horizontally, with respect to the raster.
3. To operate stability through periods of
missing horizontal sync pulses.
4. To keep the picture from drifting within
the operating temperature range.
All of these functions except for the picture position adjustment are accomplished by the phase locked loop (PLL). Delaying the horizontal sync with an adjustable timer produces the picture position adjustment.
The horizontal sync input circuit (pin 1) will trigger the picture position O/S on either the rising edge, or the falling edge, of the horizontal sync pulse. To accomplish the edge triggering, the sync pulse is differentiated by capacitor
198 into two short pulses, one for the rising edge and one for the falling edge of the sync pulse.
Which edge is the trigger depends on the bias voltage at pin 1. For positive edge triggering , the bias voltage is set to 7.8 volts by resistors
I2
I 2 and
I3
. For negative edge triggering, the bias voltage is set to 4.1V by connecting
I 12
via a solder bridge on the I PRA
The picture position O/S clamps timing capacitor
226
to 8.2 volts until horizontal sync triggers this O/S. The voltage on the timing capacitor drops at a rate set by the horizontal position control
484
and resistor
I 4
. When the voltage, at pin 2, drops below 4 volts the delayed sync O/S is triggered and capacitor
226 is reset to its clamped voltage. The delayed sync
O/S functions the same as the picture position
O/S with the exception that it is not adjustable.
The flyback pulse, connected to pin 4 through resistor
I6
, starts the negative slope of the saw tooth generator. When the sawtooth wave, which is produced by a current to capacitor
228
, drops to 3 volts, the sawtooth generator switches back to the positive slope part of the wave till the next FBP.
During the active part of the delayed sync pulse, the multiplier gates current to capacitor
231
which is dependent on the sawtooth voltage at the delayed sync pulse time.
capacitor
230
sets the "0" voltage for the multiplier which is the average value of the sawtooth waveform.
If the delayed sync pulse occurs when the sawtooth is at a low voltage part of its cycle, capacitor
231
discharges and the oscillator frequency lowers. If the delayed sync pulse occurs at the top part of the sawtooth wave no current flows to capacitor
231
.
This action, phase locks the horizontal oscillator to the incoming sync pulses.
39
4.99K
H9
GND
6-6.4VDC
X-RAY
PROTECT
HORIZONTAL DEFLECTION CONTROL SCHEMATIC
+24V
10
FLYBACK
TRANSFORMER
12
+ comp.
-
11
.36-.4VDC
.6V
63uS
EHT
+127V
9
6
8
FOCUS
7
.2V
HORIZONTAL
OSCILLATOR
DISCHARGE
63uS
8
4V 63uS
9
5.3-6VDC
7.5V
63uS
H.
V+
10
17
1.87K
235
13
.01uF
231
33K
I 8
14
1K
I 9
15
6800pF
232
I 10
HFo ADJ.
680
Ω
340
Ω
9.31K
I 16 I 15
+800Hz +400Hz
170
Ω
I 14
+200Hz
16
G F E
7
3
2
2435322 297
4
5
SCREEN
BEAM
CURRENT
FIL.
1
FIL.
The voltage on capacitor
231
controls the horizontal oscillator frequency via
I8 I
. in the case of missing horizontal sync pulses, the multiplier does not sink current and flywheel capacitor
233
holds the horizontal frequency constant. Resistor
I7 7
permits small rapid changes of the control voltage at pin 7 for locking of the oscillator to horizontal sync.
The horizontal oscillator capacitor
232 charges to its upper voltage limit through resistors
I10
,
I16
,
I15
,
I 14
and
235
. This capacitor is then discharged to the lower voltage limit through the action of discharge pin 9 and resistor
I 9 9
. The free running frequency (Hfo) may be adjusted by making solder connections on the I PRA. (see page 56 for the I PRA layout)
In some cases where there are many missing horizontal sync pulses, it is necessary to adjust the Hfo closer than ±200 Hz. For fine tuning the
Hfo, resistor
2 35
is replaced with a pot.
The horizontal phase locked loop then consists of an oscillator which sets the flyback timing.
The flyback pulse is then compared to the incoming sync pulse and the difference voltage holds the oscillator at the sync frequency.
The duty cycle of the horizontal drive transistor is generated by comparing the oscillator waveform against a fixed voltage.
This fixed voltage is set by resistors
H8 and
H 9
.
2SC2344
270
Ω
2W
157
236
12.7VDC
33V 63uS
19
HORIZONTAL
DRIVE
TRANSFORMER
2
2SD1651
20
100
Ω
I
11
.01uF
234
1
237
3
4
GND GND
304
The horizontal output transistor
304 conducts about three amps of horizontal flyback transformer primary current and deflection yoke current. This transistor has a beta as low as three. To supply the high base current a horizontal output transistor drive transformer is used. The drive transformer
237
builds up energy during the on time of the drive transistor,
236
which is the off time of the horizontal output transistor
304
.
Capacitor
2 34
and resistor
I 11
damps the drive transformer primary waveform.
The flyback transformer's main function is to supply EHT to the CRT. It also supplies the focus and screen grid voltages which are taps on the EHT supply. There are three low voltage secondaries. One supplies the filament current. Another supplies sync and EHT information to the power supply. The third secondary supplies sync for the horizontal PLL and drives the horizontal blanking circuit.
40
HORIZONTAL RASTER WIDTH CONTROL CIRCUIT DESCRIPTION
The purpose of the horizontal width control circuit is to:
1. Provide a convenient means for adjusting the horizontal raster size.
2. Correct pincushion distortion in the vertical axis.
3. Correct horizontal raster distortion caused by periods of high beam current.
The horizontal width control circuit is comprised of two main parts; The control circuit and the diode modulator (DM). The control circuit combines four signals in the monitor to produce the width control circuit. These signals are:
1. Horizontal size From the H. Size Pot.
2. Vertical current (Iv) From the 3.3 ohm vertical current feedback resistor.
3. Vertical parabolic + Iv From the vertical yoke return.
4. Beam current From the EHT return on the FBT.
The diode modulator controls the horizontal yoke current which affects the horizontal size. This is accomplished by controlling the start time of the flyback pulse in the diode modulator node at the cathode of
311
. The start time of this pulse is then a function of the forward current of the diode
311
. This is because the current in the pulse across capacitor
306
must exceed the current in the diode
311
before the pulse in the diode modulator node can start. The current used to control the start time of the pulse comes from the voltage across inductor
316
from the previous horizontal pulse and is controlled by the control circuit.
The horizontal size voltage from the remote control PCB
490
is applied directly to the control amplifier summing node (LM324 Pin 12) by resistor
G11
. For pincushion correction, the vertical parabolic voltage is needed, but it is not directly available since the vertical current,voltage (Iv) is part of the vertical parabolic voltage with respect to GND. The + Iv from the current sensing resistor
193
, is inverted by an Op Amp and resistors
148
and
1 72
. Resistor
G 3
level shifts the inverted Iv to + 6V. The (vertical parabolic + Iv) is AC coupled by capacitor
1 83
and resistor
G6
.
It is then amplified by an Op Amp connected as a voltage follower. Resistor
G7
protects the Op Amp against arc related voltage spikes. The inverted Iv (-Iv) and (parabolic voltage +Iv) are added to the amplifier node by resistors
1 67
and
166
which then makes up the pincushion correction signal.
The beam current from the FBT is converted to a voltage by resistors
G17
, adj.
159
& adj.
179
and is filtered by capacitor
162
. Resistor
G12
then connects the signal to the width control amplifier node which accomplishes the blooming control function. The control amplifier converts the current at the summing node (LM324 Pin 12) to a voltage across capacitor
315
, via feedback resistor
G13
.
A power transistor
185
is necessary since up to 2 watts may be dissipated by the control amplifier.
Resistor
G15
and capacitor
163
&
168
set the AC gain of the control Op Amp for stable operation.
Resistor
G14
stabilizes the complete control amplifier by reducing the overall gain. Resistors
G 9
,
G 10
,
1 64
and
166A
provide adjustment for setting the horizontal size range. The fourth Op Amp of the LM324 and resistors
G 1
and
G 2
are used to generate a +6 volt ref. voltage for the control circuit. Resistor
1 71
stabilizes this +6V line with a load to GND. Capacitor
161
decouples the deflection +12 volt supply by the LM324
165
. Components
G4
,
G5
,
178
,
201
, and
203
are used to correct a slight nonlinearity in the vertical deflection yoke via the vertical control circuit.
The diode modulator (DM) incorporates diode
311
to control the voltage on the DM main node
(cathode of
311
) during the flyback pulse time. If the diode
311
has low forward current, the DM node voltage will be high during flyback time and the horizontal size will be small. The forward current in the diode
311
comes from the current buildup in inductor
316
during flyback time and the voltage across the capacitor
315
during trace time. If the voltage is large across the capacitor
315 during trace time, most of the inductor current is discharged before the next retrace cycle and the horizontal size is small. This condition can be checked by connecting a DVM to the vertical heat sink
(GND) and to the heat sink
186
(collector
185
). The voltage for minimum horizontal size is about 22V.
Capacitor
315
supplies a voltage for the inductor
316
to work against similar to the 1,000uF capacitor
195
in the vertical yoke circuit. For max. horizontal size, the voltage across
3 15
is about 8V, and the diode
311
, current before retrace is high. Diodes
3 08
and
3 10
clamp the DM node to GND to keep the yoke current stable during trace time. Inductor
3 01
is an additional width coil and
3 02 is a horizontal linearity coil. Capacitor
300
and resistors
298
keep the coils from ringing after retrace. Capacitors
306
and
307
form the normal Cp. The raster may be shifted by making solder connections: left
HL
or right
HR
with increased effect
Z
. These solder connections introduces a DC current in the horizontal yoke via diode
193
or diode
312
. Resistor
303
limits the maximum current and resistor
309
permits fine adjustment.
41
HORIZONTAL RASTER WIDTH and POSITION CONTROL SCHEMATIC
VERTICAL
CONTROL
+12V
+
VERTICAL
OUTPUT
RC5
HORIZONTAL
SIZE 10K
481
GND
VERTICAL
LINEARITY
-
VERTICAL
YOKE
Remote Control
PCB 490
127VDC
1,000uF
195
+127V
FR205
H. RAS POS. CONTROL
HORIZONTAL RASTER ADJ.
FR205
FBT Pin 9
.01uF
163
100K
G10
Width
Adj.
166A
293
12K, 2W
+12V
4
289
36K
203
10uF
+
201
1K
178
10K
G3
6
8
.33uF
183
Pincushion correction.
10K
G7
220K
G6
3.3K
179
7
19
10K
184
10
7.15K
9
10
+
1/4
LM324
172
8
5
+
1/4
LM324
6
165
7
1.82K
G17
6VDC
4V 17mS
6VDC
3V
17mS
10K
9
5K
8
2092
36K
166
5
G4
+6V LINE
G5
12K
166
Horizontal
Pincushion
Parabolic
2092
22K
167
8.87K
167
Linear
2.2K
20
28K
Blooming correction.
159
.047uF
162
+
+6V
100uF
G12
169
GND
3.3
Ω
193
50K
G9
HR
314
HL
433
2092
68uH
301
Z
470
Ω
,1/2W
270
Ω
, 2W
309 303
312
HORIZONTAL YOKE
YC3
YC4
50V 170V
MAX. MIN.
H. Size
H.
WIDTH
220uH
301
H. LIN.
68uH
302
8VDC 23V
70V 250V 63uS
MAX. MIN. H. Size
2.2K
1/2W
298
3,300pF
300
.47uF
250V
305
2092
.33uF
305
1N4005
308
1N4005
310
BEAM
CURRENT
FBT Pin 4
HORIZONTAL
OUTPUT
FBT Pin 10
.01uF
1.5KV
306
2092
8.2nF
306
4
10K
G2
3
10K
G1
2
3
2, 12
4
H
+12V
+
1/4
LM324
11
SIZE
GND
1
+6V
6.8K
171
1
38.3K
G11
*
164
6.8K
19
.1uF
161
G16
13
8VDC 22V
4V 12Vp-p 17mS
MAX. MIN. H. Size
44.2K
18
12
13
+
1/4
LM324
G13
14
16K
17
.01uF
2SC2344
2.2K
15
G14
16
185
14
0
Ω
278
HEAT
SINK
186
G15
168
GND
750uH
316
2.7uF
315
1N4937
311
.022uF
630V
307
42
AC line
SIMPLIFIED POWER SUPPLY CIRCUIT FUNCTION DESCRIPTION
+127V
+
GND
Res.
FLYBACK
DIODE
266
+
LOAD
H Dy & EHT
VIDEO
GND
User supplied
Isolation
Transformer
+
Error Amp.
Comp.
C5184
DRIVER
FET
258
SECONDARIES
268
V
REF.
OSC.
ENABLE
V(-200V)
280
V292
The switching regulator includes the power FET
268
which passes current from
V- to GND through the inductor
258
. During the time the FET is on, the current in the inductor is increasing and the inductor is storing energy. When the FET is turned off, the stored energy in the inductor continues supplying current to GND.
But in this case, the current path is from V+ to GND, instead of V-to GND.
During this part of the cycle, the current in the inductor is decreasing.
Under normal conditions, the current will decrease to zero and the voltage will ring.
FET drain voltage
Current in inductor
Voltage across
292
Current in diode
266
Flyback pulse
As can be seen from the waveforms, the largest number of changes occur when the FET is turned off. Also, the FET drain voltage switches fast due to the high inductor current. To minimize video interference from the power supply, the power supply is synchronized to the horizontal oscillator such that horizontal blanking is coincident with the FET turn off time.
The C5184
280
is the series regulator IC. All of the control circuits that are built into this IC work together to produce one output signal, which is the FET drive signal. This signal can take on many shapes depending on the load conditions of the power supply. The waveforms for normal operation are shown above.
For the shorted +127V to GND condition, which also occur right on power up,
The waveforms are:
FET Gate Drive
FET Drain Voltage
Current added to the +127V line
Inductor Current
Current supplying GND
Current from V-
The first FET pulse is a full on pulse which causes current to flow in the inductor.
After the FET is turned off the current in the inductor drops much more slowly than normal since the inductor is discharging into a much lower than normal voltage.
If the FET were turned on for full power in the next cycle with current still flowing in the flyback diode, a current spike of 6A would occur, which is a power spike of
2,000W. The reason for this is that the diode stores charge when current flows which turns into reverse current for a short time when the voltage is reversed across the diode.
43
SIMPLIFIED POWER SUPPLY CIRCUIT DESCRIPTION
The FET drive waveform avoids this problem by sensing flyback diode conduction.
If the flyback diode conduction is sensed, the low current start mode is selected.
this mode turns the FET on, to a current of .1A, for not more than 4uS. If before or during the low current FET on time, the flyback diode breaks free, and the FET drain voltage goes down, the flyback diode voltage comparator will signal the regulator to permit the FET to be turned on for a full power cycle.
The cycle after the last low power cycle in the waveform above is an example of this condition. The flyback diode voltage comparator inputs are located at pins 12 & 13 of the C5184. The two resistor dividers
J10
,
J11
and
J12
,
271
connect the comparator across the flyback diode. The comparator enables the FET drive only after a 10% voltage drop is measured across this diode.
Another fault condition exists when the FET exceeds 1.6A drain current.
This condition can occur if the oscillator frequency is too low, the FET drain is shorted to GND or V+, the transformer has a shorted secondary, or the core is broken.
In these cases the voltage across the FET source resistor
292
exceeds 1.6V which is sensed by the over current comparator at pin 11. If pin 11 exceeds 1.6V, the FET drive is set to 0V for the rest of the cycle. In some cases, this condition can produce an output waveform which looks normal, but the voltage across the load
(+127V to GND) would be low or unstable. A quick check for this condition is to check the peak voltage across the FET source resistor. CAUTION; Whenever connecting a scope ground to V-, be sure that the other scope probe or common grounded devices are not connected to the monitor GND.
Most of the power supply fault conditions cause the power supply to chirp because the source of +17V for the regulator IC is generated by the power supply.
A special circuit is built into the regulator IC, which permits charging the +17V line filter capacitor with only a very low load from the IC. This circuit turns the rest of the IC on only after the voltage at pin 15 reaches 17V. If the transformer does not supply at least 12V to this line before the filter capacitor discharges to 12V, the regulator IC turns off. The reason for the audible chirp, is that, the power supply is not full on for each cycle which produces a frequency low enough to hear.
A 19V to 20V @ 1A, DC, isolated power supply is a tool necessary for trouble shooting
CERONIX monitors. When trouble shooting the power supply, it can be connected to
V- and the +17V line to keep the power supply running while checking the voltages and waveforms to find the fault. It can also be used to supply the GND to +24V line for checking the horizontal circuit. If the horizontal circuit does not work, the power supply will chirp. Without the horizontal circuit working, there is not enough load on the power supply for transformer action to keep the regulator IC
+17V line up to the minimum of +12V. A quick check for this condition is to clip a 2-4K@10W power resistor from GND to +127V line. If the chirping stops, the horizontal is probably not working.
The heart of the power supply is the oscillator which supplies the basic timing.
The FET drive is always low during the negative slope of the oscillator or, when synchronized, after the start of the sync pulse. The low to high transition of the
FET drive, pin 10, is determined by the voltage at the output of the error amplifier.
If the 127V line goes up in voltage, the error amplifier voltage goes up, which then intersects the oscillator waveform at a higher voltage and causes the FET on time to start later and be shorter. This negative feedback accomplishes the control loop of the power supply.
The regulator IC has a built in reference voltage which is used by the error amplifier set and hold the +127V line constant. Solder connections on the J PRA are used to adjust the +127V line in steps of ±1.5V.
The over voltage protect circuit, when activated, turns off the regulator IC until power is disconnected. This circuit is connected to the rectified flyback pulse, which outputs a voltage that is proportional to the EHT. The circuit's main purpose is to protect the user against excessive x-ray which is caused by excessive EHT.
44
SWITCH MODE POWER SUPPLY CIRCUIT DESCRIPTION
127V
The series regulator IC
280
, controls current to the monitor GND by pulse width modulation.
A PNP transistor
250
, has an emitter current, that is directly proportional to the 127V line voltage due to resistor
J1
and adjustment resistors
J13
&
J14
. This current is transmitted to the power supply V- line, and is applied to a resistor
J5
,
J15
, &
J16
. The voltage across these resistors is compared to a reference voltage by the error amplifier. If the +127V line goes up the output of the error amplifier voltage goes up. The pulse width modulation, which controls the + 127V line voltage, is accomplished by turning the FET drive on at some particular voltage along the rising slope of the oscillator waveform. This particular voltage is the error amplifier output voltage.
Oscillator waveform without sync:
Oscillator waveform with sync:
Error Amp. V.
FET drive, C5184 pin 10:
Fet Drive
With Sync
The FET drive is always off during the negative slope of the oscillator, or just after the sync pulse.
Since the FET drive pulse is started by the error amplifier voltage and terminated by the end of the oscillator cycle, a control system via pulse width modulation has been established. The oscillator waveform is produced by charging capacitor
277
with a constant current set by resistor
J7 to a voltage of 5V and then discharging the capacitor with double the charging current to 2.5V.
Adding the flyback pulse, via capacitor
288
to this waveform synchronizes the oscillator, since the oscillator frequency is set below the horizontal frequency.
Resistors
J2
,
J4
and capacitor
274
limit the error amplifier's AC gain, to hold the control loop stable. Capacitor
275
holds the error amplifier stable. Capacitor
281
reduces power supply noise, but, if too large, will cause the power supply to be unstable.
The 127V line is adjusted by making solder connections on the J PRA
(refer to page 56 for the layout)
A
A
and B are used to
FR205
252
2,200pF raise the 127V line up to 4.5 volts in steps of 1.5 volts. Connections
C
and
D
lower the 127V line as much as 4.5V. The 127V line
220Vo
252A should be adjusted if below 125.8V or higher than 128.2V.
Resistors
273
and
249
are used for monitors with special
246
253
127V line voltages.
CUT
FOR
220Vo
+
150uF
256
100K
1/2W
247
The FET
268
works together with the transformer
258 to provide a low resistance current path from V- to GND.
This low resistance coupled with no large voltage times current products is what makes the power supply efficient.
INRUSH
CURRENT
LIMIT
2,200pF
254A
FR205
250V
+
150uF
7
8,14
90K
Resistor
292
provides a means for sensing the FET current.
In the low current mode, it is used to set the 100mA current
25-.5
Ω
GL200
240
257
250V
J6 and in the full on mode it is used to sense the max. current.
Resistors
264
,
270
and capacitor
265
reduce power supply
254
+
100uF
286
220Vo electrical noise. Transistor
284
and diode
283
short the
FET drive to V- when the monitor is turned off to protect the
3A FUSE
245 255
FET from conducting current with a still large drain voltage.
Resistors
J10
,
J11
,
J12
and
271
provide a means for checking flyback diode
266
conduction via a comparator.
To deguassing coil and posistor.
If the comparator measures low flyback diode voltage the
FET is turned on to the .1A low current mode. This mode is necessary during power up, since initially the +127V line
PC
2
241
115VAC
INPUT
PC
1
238 is 0V and no reverse diode voltage exists. The over voltage protect circuit has a trip voltage of 8V
Vand when it is activated, it shuts down the power supply. The EHT is measured by rectifying the flyback pulse, with diode
290
, from a secondary winding of the FBT. Capacitors
291
,
285
and resistors
287
,
J9
are connected as a low pass filter to smooth out the simulated EHT voltage which is then applied to the C5184 at pin 14. Resistor
J8
protects the IC current sense input from voltage spikes and resistor
251
protects the PNP transistor from momentary overvoltage damage due to line spikes. Zener diode
295
protects the horizontal and video circuits from overvoltage due to power supply failure. If the +127V line exceeds 160V, the zener diode
295
shorts to GND the +127V line.
45
127V
C -1.5V
2.33K
D -3V
4.67K
193K
J1
J13 J14
*
17V
249
1
2SA1371E
250
100K
251
2
10.6K
J5
6
.01uF
20
TZ160B-T3
160V
295
SWITCH MODE POWER SUPPLY SCHEMATIC
+24V
+127V
+16V
+27V
FR205
150uF
250V
317
.1uF
250V
294
+
1,000uF
215
.1uF
263
262
+
+16V
1,000uF
131
.1uF
261
FR205
260
GND
6.5-7.5VDC
1
INPUT
ERROR
AMP.
16.3-17.8VDC
+15V
+17V
INPUT
16
15
14.8-16.3VDC
18
Ω
248A
260
Ω
J16
130
Ω
J15
1.87K
273
B
+3V
11K
J2
23.2K
J3
A
+1.5V
6.5-7.5VDC
2
5
4
56K
J4
.5-.8VDC
3
6,800pF
56pF
274
4
3.4-4.2VDC
INPUT
COMP.
Output
Over
Voltage
Protect
}
14
INPUT
6-7VDC
+127V
.022uF
296
V-
56pF
.1-.5VDC
5
CONTROL &
FAULT SENSE
4uS
DELAY
COMP.
+
12
13
3.6-4.4VDC
6V 63uS
5.3-5.7VDC
276
33.2K
9
5.7-6.3VDC
6
Rx
OUTPUT
.10-.17VDC
1V 63uS
J7
6,800pF
277
FROM
FBT
Osc.
Current
SENSE
11
3.5-4.1VDC
3-4V 63uS
7
Cx
DRIVE
10
330pF
288
0VDC
48V 63uS
8
+7.5V
REF.
XRC5184
V-
280
9
V-
2.4-3.6VDC
14V 63uS
J PRA PINS: 3,10,15, & 19
FR205
3
SMXFR
5
9
4
248
1
2
258
20
.1uF
285
1.00M
J10
17
MPSA64
2,200pF
282
D
191K
16
287
38.3K
J9
1.00M
271
18
270
1N4005
283
284
V-
268
1.2
Ω
292
+127V
1,000 pF
291
14.7K
15.8K
J11 J12
12
510
Ω
J8
13
2SK1446
18
Ω
GND
FROM
FBT
FR205
266
1N4148
290
Heat
Sink
267
200pF
265
150
Ω
264
POWER
SUPPLY
LOW VOLTAGE
SECONDARIES
VOLTAGE CURRENT
17VDC 7mA
CIRCUIT SUPPLIED
POWER SUPPLY CONTROL
16VDC
27VDC
250mA
250mA
VIDEO AND INPUT
V. &H. DEFLECTION
DIODE FILTER CAP.
NOISE CAP.
248
260
263
100uF
1,000uF
1,000uF
286
131
215
NONE
.1uF
.1uF
261
262
At the input to the power supply is a voltage doubler which outputs between 240 to 425VDC depending on the AC line voltage. It has a three amp fuse
245
to protect the PCB traces, an inrush current limiter
240
to protect the rectifier diodes
252
,
254
, and optional capacitor
241
and inductor
246
which can be used to reduce conducted noise from the monitor AC input. For 220VAC operation the voltage doubler is replaced by a full wave rectifier by adding diodes
253
,
255
and cutting the 220Vo trace.
256
&
257
are the raw DC filter capacitors. Resistor
J6
supplies the power supply start current and resistor
247
balances the series connected filter capacitors for 220VAC operation.
46
OSCILLOSCOPE
Equipment setup for repairing the Model 1492 Monitor
+127.0
DVM
VARIABLE
TRANSFORMER
ISOLATION
TRANSFORMER
ISOLATED
+20V @.5A DC
POWER
SUPPLY
115
VAC
CERONIX Model 1492
ISOLATED +20V POWER SUPPLY CIRCUIT.
1N4005
1A Std. Fuse
Power SW
115 VAC
60 Hz
20V @ 1A
Transformer
Triad #F-254 X
1N4005
1N4005
1N4005
1,000uF
35V
-7V
ADJ.
IN OUT
LM337MT
HEAT SINK
+20V
4.75K,1%
47K
10K
1uF
1A Std. Fuse
20 Volt
@.5 A
301R,1%
1N4749A
24V Zener
0V
47
Problem Solving Tools
SAFETY FIRST; Use only one hand when working on a powered up monitor to avoid electrical shock.
Always wear safety glasses.
Many of the failures that cause burnt components and boards are eliminated by the load sensitive switching mode power supply in the CERONIX monitor. This feature can cause problems with servicing the monitor if the proper trouble shooting approach is not used. The equipment setup, shown here, is necessary for efficient trouble shooting of the CERONIX monitors.
Problems that cause the power supply to chirp are:
1. Insufficient +127V line load.
2. Overloaded +127V, +24V, or +16V lines.
3. Shorted +127V, +24V, or +16V lines.
4. Power supply component failure.
5. Raw DC (+127V to V-) voltage too low.
1.
A quick check for the insufficient +127V load is to connect a 2K to 4K ohm 10 watt power resistor to GND and the +127V line. If the chirping stops, proceed to check the horizontal deflection circuit. First disconnect the board from the AC supply. Then connect the +20V supply,
0V line to GND, and the +20V line to +127V and +24V lines on the monitor. Now the complete horizontal and vertical circuits can be checked with the oscilloscope and DVM.
The flyback waveform will be about 140Vp–p instead of 1,000Vp–p which permits checking even the horizontal output transistor, collector, waveform.
2.
For the overloaded supply line problems, which often occur only when the +127V line is fully powered up, the +20 volt external power supply is used to keep the monitor power supply running.
To use the external supply, connect the 0V line to V- (anode of diode
254
) and the +20V line to the monitor power supply +17V line (cathode of diode
248
).
Connect the oscilloscope GND to V- and the probe to the FET drive (anode of diode
283
).
TAKE CARE NOT TO TOUCH THE OSCILLOSCOPE AND MONITOR CHASSIS DURING THIS
TEST, SINCE
THE VOLTAGE DIFFERENCE CAN BE AS HIGH AS 400 VOLTS.
Increase the AC supply, slowly, to the normal operating voltage while monitoring the +127V line to GND voltage with the DVM. The power supply overload condition can be seen on the scope as an almost square wave which can break up into short and long pulses as the AC line voltage is increased. The short pulses are the flyback diode current sense pulses. Sometimes the monitor will operate normally in this mode, in which case, watch for smoke and after a few minutes of operation disconnect the power connections and carefully feel around the conductor side of the board for hot spots. Overload conditions will not harm the power supply unless there is a problem in the power supply.
3.
If the +127V crowbar zener
295
is shorted, a fault exists in the power supply which permitted the +127V line to exceed +160V. First replace the zener. Never operate the monitor without the crowbar zener installed. Then with the external supply, the DVM, and the scope connected to the power supply (as in 2) slowly increase the AC line and observe the power supply
response. Do not exceed +145V on the +127 V line. If the monitor runs normally, a fault may still exist in the power supply power down circuit. Check parts
283
and
284
. If the crowbar zener is shorted and the FET is internally shorted, the C5184 IC
280
should also be replaced.
If there is no FET drive waveform, check the voltages and waveforms on the C5184 pins and compare them to the voltages and waveforms on the schematic.
Shorts on the +127V, 24V, and 16V lines other than the crowbar zener are not likely to be connected to the power supply even though the power supply chirps. By operating the power supply with the +20V external power supply many of these problems can be found using the same procedure as are used in trouble shooting monitors with linear power supplies.
4.
The power supply may chirp if: The transformer core is broken or a winding is shorted.
The 1.2 ohm current sensing resistor value is too high.
The +17V line is open. (goes away when ext. PS is used)
5.
There is a line voltage range of about 60% to 70% AC line voltage where a correctly
operating monitor will chirp.
48
SETUP AND CONVERGENCE PROCEDURE
1. Use a knife to brake free the magnetic rings on the yoke which are locked
with red varnish. Bring the adjustment tabs on each pair of magnetic rings
in line for the starting point.
2. Loosen the yoke clamp. Remove the yoke wedges and the tape from the CRT.
3. Connect a test generator to the video input and clip the red lead to the
+12V line (anode of diode
101
).
4. Turn the monitor on. Switch the test generator to red field.
Adjust the horizontal and vertical raster size, on the remote control board,
for under scan. Let the monitor run for at least half an hour.
5. Check the auto bright control voltage with a DVM connected to GND and pin 8
of the LM324
146
. The voltage range is 4.3V to 4.9V. If out of range,
adjust this voltage to 4.6V by using pliers to rotate the bottom knob on the FBT.
6. Degauss the picture tube and front part of the frame.
CAUTION: To avoid electrical shock , take care not to touch the yoke conductors
or push against the anode cap. Always keep one hand away from unit.
7. Adjust the yoke position, on the CRT neck, to the center of purity. One way to
locate this yoke position is to make a felt pen mark on the CRT neck at the
rear extreme of purity and another mark at the front extreme of purity.
Make a third mark between the two marks and set the yoke to this position.
Rotate the yoke to line up, the raster top line, with the top of the picture tube.
Tighten the yoke clamp. Tilt the yoke side to side and up and down while
watching the red field to verify that purity is good.
8. On the 13 inch CRT, use the purity magnets (closest to the yoke coils) to center
the raster horizontally. To accomplish this, find the rotational position
where spreading the tabs has the most effect on the horizontal position
and spread the tabs a minimum to center the raster horizontally. On the 20 inch
CRT, the purity magnets are often needed to optimize purity. The horizontal
raster position solder connections are used to adjust the raster position.
These solder connections are located on the foil side of the PCB next to the FBT.
Connection HR shifts the raster right, HL shifts the raster left and the range of this
shift can be increased by making solder connection
Z
under resistor
309
.
9. Check the purity with red field and with blue field while tilting the yoke side
to side and up and down.
10. Switch the generator to red/blue grid. Adjust the 4 pole magnets (center pair)
for convergence of the red and blue guns in the center of the screen.
11. Tilt the yoke up and down for the best convergence around the edge of the grid.
Insert the top yoke wedge. Tilt the yoke side to side for the best
convergence around the edge of the grid and insert the rest of the yoke wedges.
Secure the wedges with tape.
12. Switch the generator to white grid. Adjust the 6 pole magnets (Pair closest
to the socket board) for convergence of the green gun.
Step #10 and this step may have to be repeated for optimum convergence.
49
1492 & 2092 VIDEO INTERFACE PROGRAMS
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
F C
D A
P
T U
S
AA
AC Coin & Slot Service;
4 Solder Connections: Q, X, Y, & S.
Standard Board.
(1492)
X
O
L
N K
H
Q
I
Y
R
G
J M
B
E
F C
D A
P
T U
S
AA
Advanced Touch Systems; (1492)
Change 007 , 024 , & 037 from 340
Ω
to 205
Ω
±1%
Change 008 , 023 , & 034 from 12.1K to 7.15K ±1%,
12 Solder Connections: A, B, C, G, H, I, J, K, L, P, T, & Y.
X
O
L
N K
Q
I
Y
R
G
J M
H
B
E
F C
D A
P
T U
S
AA
Aeries International; (1492)
11 Solder Connections: D, E, F, G, H, I, M, N, O, P, & Y.
Standard Board.
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
T U
S
F C
D A
P
AA
NOTE: Solder connections S, T, & U, and resistor 094
set the video gain and may change due to
component variations.
Altec; (1492)
11 Solder Connections: D, E, F, G, H, I, M, N, O, P, & Y.
Standard Board.
HFo = 15,370 ±200Hz.
50
1492 & 2092 VIDEO INTERFACE PROGRAMS
Aristocrat; (1492)
Install three 100pF disc capacitors at 010 , 022 , & 041 .
Invert horizontal sync by adding a solder connection on the "I" PRA above pin 5.
Install posistor at 244 .
11 Solder Connections: D, E, F, G, H, I, M, N, O, P, & Y.
Before final test, clip out 045 , 270 ohm resistor, and add one solder connection AA by component no. 060 .
High resolution board.
Automation; (1492)
Change 002 From 75
Ω
to 130
Ω
..
Change 027 From 75
Ω
to 47
Ω
.
Change 094 from 2.7K to 10K.
Install posistor 244 .
11 Solder Connections: D, E, F, G, H, I, M, N, O, P, & Y
Before final test add solder connections B & C.
High resolution board.
X
O
L
N K
Q
I
Y
R
G
J M
H
B
E
F C
D A
P
T U
S
AA
Bally;
(1492)
12 Solder Connections: D, E, F, G, H, I, J, K, L, P, T, & Y.
Add a solder connection on the "I" PRA above pin 5.
Install posistor at 244 .
High resolution board.
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
T U
S
F C
D A
P
AA
NOTE: Solder connections S, T, & U, and resistor 094
set the video gain and may change due to
component variations.
Brunswick; (1492)
Change 007 , 024 , & 037 from 340
Ω
to 301
Ω
±1%
Change 235 , from Hfo set resistor to 3K pot.
Remove the 2.7K resistor at 094 .
Add a solder connection on the I PRA above pin 5.
11 Solder Connections: A, B, C, G, H, I, J, K, L, P, & Y.
Before final test, add the AA solder connection and cut out the 270
Ω
resistor at 045 .
Standard board.
51
X
O
L
1492 & 2092 VIDEO INTERFACE PROGRAMS
F C
Q
I
Y
N K
R
G
D A
J
M
H
B
E
P
T U
S
AA
By Video;
(2092)
Change 008 , 023 , & 034 from 12.1K to 2.67K,1%
Change 002 , 005 , & 027 from 75
Ω
to 2.7K, 5%, 1/4W
Change 203 from 36K, 5% to 24.3K, 1%.
Install posistor at 244 .
12 Solder Connections: A, B, C, G, H, I, M, N, O, P, T, & Y.
Before final test, clip out 045 , 270 ohm resistor, and add one solder connection AA by 060 .
For the 13" CRT monitor, Add solder connection
S, and omit T . do not change resistor 203
X
O
L
N K
H
Q
I
Y
R
G
J M
B
E
T U
S
F C
D A
P
AA
12 Solder Connections: Q, X, Y, & S.
N K
H
X
O
L
Q
I
Y
R
G
J M
B
E
F C
D A
P
T U
S
AA
Carson Valley Inn; (1492)
Change 200 from 127K to a 200K pot.
4 Solder Connections: Q, X, Y, & S.
High resolution board.
CAS Ltd.;
(1492)
Add a solder connection on the I PRA above pin 5.
Change 094 from 2.7K to 10K.
11 Solder Connections: D, E, F, G, H, I, M, N, O, P, & Y.
Standard board.
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
T U
S
F C
D A
P
AA
NOTE: Solder connections S, T, & U, and resistor 094
set the video gain and may change due to
component variations.
CEI; (1492)
Change 094 from 2.7K to 10K.
Install the posistor at 244 .
11 Solder Connections: D, E, F, G, H, I, M, N, O, P, & Y.
52
1492 & 2092 VIDEO INTERFACE PROGRAMS
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
F C
D A
P
T U
S
AA
Games of Nevada; (1492)
12 Solder connections: D, E, F, G, H, I, J, K, L, P, T, & Y.
High resolution board.
X
O
L
N K
H
Q
I
Y
R
G
J M
B
E
F C
D A
P
T U
S
AA
IGT; (1492)
Delete degaussing circuit.
4 Solder Connections: Q, S, X, & Y.
High resolution board.
X
O
L
N K
Q
I
Y
R
G
J M
H
B
E
F C
D A
P
T U
S
AA
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
T U
S
F C
D A
P
AA
NOTE: Solder connections S, T, & U, and resistor 094
set the video gain and may change due to
component variations.
Keevex; (1492)
Install posistor at 244 .
4 Solder Connections: Q, S, X, & Y.
Horizontal frequency is 17,182Hz
High resolution board.
Mast Keystone; (1492)
Change 002 , 005 , & 027 from 75
Ω
to 1K ±5%.
5 Solder Connections: A, B, C, P, & S.
Standard Board.
53
1492 & 2092 VIDEO INTERFACE PROGRAMS
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
F C
D A
P
T U
S
AA
RS 170;
(1492)
Change 007 , 024 , & 037 from 340 ohm to 140 ohm ±1%.
Change 008 , 023 , & 034 from 12.1K to 3.32K ±1%.
Remove 045 , 046 , 047 , & 048 .
Add a 2.2K resistor to hole by video connector 006 pin 5 and hole between resistors 050 & 051 .
12 Solder Connections: A, AA, B, C, G, H, I, J, K, L, P, & Y.
X
O
L
N K
H
Q
I
Y
R
G
J M
B
E
F C
D A
P
T U
S
AA
Semi-Conductor;
(1492)
Change 002 , 005 , & 027 from 75
Ω
to 27
Ω
±1%.
Change 007 , 024 , & 037 from 340
Ω
to 140
Ω
±1%.
Change 008 , 023 , & 034 from 12.1K to 3.32K ±1%.
Change 064 from 2.7K to 10K ±5%.
Install posistor at 244 .
11 Solder Connections: A, B, C, G, H, I, J, K, L, P, & Y.
High resolution board.
X
O
L
N K
Q
I
Y
R
G
J M
H
B
E
F C
D A
P
T U
S
AA
Syntec;
(2092)
Change 203 from a 36K ±5% to a 24.3K ±1% resistor.
Change 094 from 2.7K to 10K ±5%.
Delete degaussing circuit.
5 Solder Connections: Q, U, R, X, & Y.
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
T U
S
F C
D A
P
AA
NOTE: Solder connections S, T, & U, and resistor 094
set the video gain and may change due to
component variations.
United Tote;
(1492)
Change 002 , 005 , & 027 from 75
Ω
to 1K ±5%.
Change 008 , 023 , & 034 from 12.1K to 4.42K ±1%.
12 Solder Connections: A, B, C, G, H, I, M, N, O, P, U, & Y.
54
1492 & 2092 VIDEO INTERFACE PROGRAMS
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
F C
D A
P
T U
S
AA
Western Amusement (1492)
Change 094 from 2.7K to 10K, ±5%.
Install posistor 244 .
11 Solder Connections: D, E, F, G, H, I, M, N, O, P, & Y.
Standard board.
X
O
L
N K
H
Q
I
Y
R
G
J M
B
E
F C
D A
P
T U
S
AA
4 Line TTL; (1492)
Change 002 , 005 , & 027 from 75
Ω
to 1K ±5%.
Change, the video input connector, 006 from a 6 conductor
to a 7 conductor header.
5 Solder Connections: A, B, C, P, & S
X
O
L
N K
Q
I
Y
R
G
J M
H
B
E
F C
D A
P
T U
S
AA
X
O
L
N K
Q
I
Y
R
G
J
M
H
B
E
T U
S
F C
D A
P
AA
NOTE: Solder connections S, T, & U, and resistor 094
set the video gain and may change due to
component variations.
Solder Connections:
Solder Connections:
55
NOTES:
56
1.2K
B4
790
Ω
B9
1490-91
3.78K
B19
40.2K
7 6 5 4 3
2 1
NE592
1.27
K
B8
1.65K
B11
B17
5.62K
B12
836
Ω
B10
8 9 10 11 12 13 14
68K
27
Ω
B3
B1
606
Ω
B6
1490-91
392
Ω
B5
539
Ω
B20
B2
1
PNP drive cap.
2
NPN
E
3
7.9V
LINE
4
NPN
B
5
NE592
Output
6
GND
7
+12V
LINE
8
VIDEO
INPUT
9 10
GND
3.32
K
B7
11
AUTO
BIAS
270
12
GND
13
127V
LINE
Ω
32
Ω
B18
B13
B14
14
7.9V
15
PNP E
CAP.
16
PNP B
DIODE
17
PNP
B
66
Ω
B15
510
Ω
B16
18
PNP
E
19
PNP
C
20
AMP
Output
B
P/N CPR0500
VIDEO AMPLIFIER RESISTOR ARRAY "B"
200
Ω
C16
68.1K
C1
200
Ω
C13
68.1K
C2
68.1K
200
Ω
C8
C3
20K 1.82
K
C5
C6
2.74K 1.82
K
C7 C4
1
Program
PULSE
2
H.
Blank
3
Program
PULSE
4
BLUE i Beam
5
GREEN i Beam
6
Program
PULSE
7
RED i Beam
8
GND
9
NC
10
10.7V
LINE
4
11
4.2V
LINE
5
5.00K
C9
4K
C10
4K
C11
5.00K
C12
12
RED
Amp out
7
13
RED
Amp FB
6
14
RED i sense
15
GREEN i sense
LM324 Pin No.
16
GREEN
Amp FB
2
17
GREEN
Amp out
1
AUTO BIAS RESISTOR ARRAY "C"
4K
C14
5.00K
C15
18
BLUE i sense
19
BLUE
Amp FB
13
C
20
BLUE
Amp out
14
P/N CPR0503
10K
G1
10K
G2
1
H. SIZE
POT
2
GND
3
+6V
Source
3
4
+12V
LINE
5
7
220K
10K
G7
G6
5K
G5
10K
G4
Solder connection
A
reduces the horizontal raster size.
10K
G3
10K
G8
38.3K
G11
50K
G9
28K
G12
A
100K
G10
44.2K
G13
2.2K
G14
16K
G15
1.82
K
6.8K
G16 G17
6
Pincush.
Couple
Cap.
7 to Pin.
Buffer
5
8
8
9
V. LIN.
Correct.
10
LIN.
buffer node
9
11
NC
12
GND
13
DM
Buffer
12
14
DM control
V FB
15
DM amp
Output
14
16
NPN
B
17
Stability
Cap.
LM324 Pin No.
18
DM amp
Neg FB
13
HORIZONTAL WIDTH CONTROL RESISTOR ARRAY "G"
P/N CPR0504
19
+6V
LINE
1
20 i Beam
FB
G
57
Precision Resisitor Arrays (PRAs).
1
VERT.
SIZE
2
SYNC
INPUT
4
V. OSC.
RES.
5
VERT.
SYNC
19
Solder jumpers B and C are used to keep the vertical oscillator (with no sync) within the range of 43 to 47Hz.
B - Decreases Vfo. C - Increases Vfo.
330
Ω
H2
330
Ω
H1
H21
B
.5M
H
19
.2M
H
18
C
22K
H17
84K
H3
6
+12V
LINE
20
22K
H14
B
3906
E
H22
C
C
3904
E
H23 B
22K
H15
+
22K
H16
7
V. OSC.
CAP.
18
8
RAMP
CAP.
9
Output bias
Control
17
10uF
16V
H24
301
Ω
H5
10
RAMP
CAP.
88K
H20
1N4148
H25
118K
H4
1K
H12
76.8K
H6
.2M
H
13
330
H7
H26
4.99K
H9
4.75K
H8
34K
H10
1K
H11
11
BIAS
O/S
16
12
V. OUT
LA7851
15
13
LA7830
INPUT
14
+12V
LINE
15
GND
13 14
16
H. Duty
Cycle
11
17
BIAS
H.F. FB
18
TO
YOKE
LA7851 Pin No.
Vertical Control Resistor Array "H"
19
YOKE
Return
20
YOKE i sense
H
P/N CPR0503D
D - Inverts Horizontal Sync.
E, F, & G Adjust the Horizontal Oscillator Frequency.
E=Hfo +200 Hz, F=Hfo +400Hz, & G=Hfo +800Hz.
45K
I
6
1.8K
I
1
12K
I
2
1
FBP
2
H. Pos.
POT
3
H. Sync
Cap.
D
8.8K
I
12
22K
I
3
2.7K
I
4
H.
5
+12V
6
GND
7
H. Sync
Output
1
8
H. Pos.
O/S
2
6.8K
I
13
E F
340
Ω
I
15
680
Ω
I
16
G
9.31K
I
10
200
Ω
200
Ω
170
Ω
I
14
1/2
I
11
25K
I
5
9
PLL
O/S
3
1/2
I
11
10K
I
7
33K
I
8
1K
I
9
10
GND
11
PLL
SYNC
4 LA7851 Pin No.
13
PLL output
Cap.
7
14
OSC.
8
15
Osc. Discharge
9
16
Hfo
SET
17
H. +12V
Line
18
Flywheel
Cap.
19
H. Drive
Damper
20
Damper
Cap.
I
P/N CPR0502
Horizontal Control Resistor Array "I"
C - Decreases +127Vline by 1.5V
D - Decreases +127Vline by 3V
A - Increases +127Vline by 1.5V
B - Increases +127Vline by 3V
193K
J1
2.33K
1
+127V
SENSE
2
Old
+127V
SET
C
11K
R2
J2
23.2K
J3
3
V-
J14
D
56K
J4
J15
260
Ω
J16
10.6K
J5
A
B
45K
J6A
4
E. Amp.
-FB cap.
5
E. Amp
Output
2
6
E. Amp
+Input
1
7
1/2 Raw
DC
8
17V
V-, 100V to 300V below GND.
9
Osc.
Rx
1M
POWER SUPPLY. RESISTOR ARRAY "J"
J10
P/N CPR0501
45K
J6B
38.3K
J9
14.7K
J11
15.8K
J12
510
Ω
33.2k
J7
10
V-
C5184 Pin No.
12
FET i
Sense
11
13
FET
Source
14
+17V
15
15
V-
16
O.V.P.
LOAD
14
17
D
266
+ Comp.
13
Normally GND -200V.
Power Supply Resistor Array "J"
18
D
266
- Comp.
12
19
V-
20
V+
127V
J
P/N CPR0501
58
advertisement
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
