Crown D-Series Instruction manuals

crown
SECTION 7
MAINTENANCE
7.1 Introduction
Section 7 contains technical information required to
effectively and efficiently service and repair the Crown D-
150A Included are disassembly and reassembly
procedures, required test equipment lists, checkout
procedures, basic troubleshooting tips and a soldering
technique review. :
THIS INFORMATION IS INTENDED FOR USE BY
AN EXPERIENCED TECHNICIAN ONLY!
Use this information in conjunction with the Instruction
Manual, schematic/board layout diagrams, parts lists
and exploded view drawings (the latter located in Section
6 of this manual).
| EQUIPMENT REQUIREMENTS
Oscilloscope Capable of displaying a
| 10M Hz signal
Low-voltage resistance probe
(100mv range). High-voltage
resistance probe (1.5V range)
| Volt-ohmmeter
| (VOM)
| Freq. Counter
Sine/ Square wave available;
flat frequency response. THD.
‚19% maximum
| Signal Generator
| Circuit Breaker - 15 ampere rating
Peak reading meter (displays
rms equivalent to a sinu-
soidal peak for any wave
form)
| AC Line Voltage
| Monitor
APPLICATION
7.2 Required Test Equipment
Many of the service and repair problems with the D-150A
can be performed with a limited amount of test
equipment. However, in order to return the unit to its
“factory new” specifications, the following list of
required test
equipment is
recommended. The
“Requirements” column provides information to allow
intelligent selection of substitutes if the “Suggested
Supplier and Model” is not available or is considered
impractical to obtain,
Monitoring output during
service and testing
Check resistance values (low
voltage probe). Check semi-
conductor junctions for
opens or shorts (high volt-
age probe) Check DC
voltages
For accurate general
monitoring
Provide test signals for
service and checkout
In AC line to unit;
" protects circuitry from
overload if power supply
has shorted
Monitor Line voltage
SUGGESTED MODEL
Telequipment DS4A or
equivalent
Triplett 601 or
equivalent
Heath УМ ЗА
Wavetek 130-Series or
equivalent
Available from CROWN
7-1
EQUIPMENT REQUIREMENTS
Phase Meter |
100ту low range, flat fre-
quency response to 100K Hz
AC Voltmeter
| Filter 20-20K Hz bandpass, low noise
20Hz-20K Hz
Intermodulation Residual (.0029% or lower)
| Distortion Analyzer
7.3 Soldering Techniques
Note: Proper continuity between internal components
of any electronic device is the key to its successful
operation. Therefore, a brief review of the following
discussion on soldering techniques may be in order.
Because most service work involves component part(s)
replacement, hand-soldering with the use of a soldering
iron will be the only method covered, even though many
exist.
The difference between success and failure in service
repair is often determined by the thermal characteristics
of an iron and how well it matches the job at hand. One
would not use a large flat-head screwdriver to work on a
delicate Swiss watch. Likewise, the proper size iron and
tip should be used when soldering delicate electronic
parts in position.
Iron wattage classification is actually not a very good
method of choosing an iron. The reason for this is
because of the possible inefficiency of heat transfer to the
tip internally. A large wattage iron (125W) may, in effect
produce lower tip temperatures than another iron smaller
in wattage. Likewise, tip size and shape does not
necessarily work in proportion to temperature.
Therefore, it is impractical to compare soldering irons by
their wattage but more feasible to refer to them by their
maximum tip temperature.
Usually, the skilled service technician can pick the right
iran and tip for the job from experience o:
recommendation. In most cases, the miniature or small
electrical soldering iron will work well with delicate
semiconductor devices (Fig. 7.1). When the proper size
iron is used (usually around 700° F. tip temperature), a
joint 1s almost instantly heated (approx. 500-550°) and
application of iron and solder melting is simultaneous.
7-2
APPLICATION
Set output level for test-
ing; check noise level
Between preamplifier and
voltmeter in noise test
Check IM distortion
SUGG ESTED MODEL
Hewlett-Packard 400F
or equivalent
Information available
from CROWN
Information available
from Crown
Fig. 7.1 Miniature Soldering Iron
When clean metal is exposd to air a chemical reaction
takes place known as oxidation. When heat is applied to
metal, oxidation is speeded up and creates a non-metallic
film that prevents solder from touching the base metal.
By applying a small amount of solder to a hot iron tip, a
desirable process known as tinning occurs. The main
reason for tinning an iron is to help prevent it from
oxidizing as well as to aid in heat transfer. Tinning should
be performed prior to each use as well as after long idling
times.
To help prevent oxidation or remove existing oxidation
while soldering, a natural rosin flux core solder should be
used. Not only does flux aid in cleaning, but acts as a
catalyst in that it helps speed up the joint formation
without actually entering itself, into the bond. Never use
an acid flux except to clean a highly oxidized tip that will
not tin correctly. Crown recommends 63% tin/37% lead
composition with a rosin flux core of 2.5% (melting
temperature is approx. 361°F.).
Fig. 7.2 shows the correct and incorrect method of
applying rosin flux core solder to a joint. Never apply
solder to the iron tip directly and allow solder to run onto
the joint (flux is burned away and does not clean the
joints). Always apply heat to the connection and allow
the joint to melt the solder, not the iron. This insures
proper wetting and flow of the solder.
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Fig. 7.2 Correct and Incorrect Solder
Application
Problem: Unsoldered wire.
Characteristics: Properly assembled junction of wire, but
One of the main advantages of using solder to make
connections is that it is one of the few joining methods
responsive to visual examination. This permits 100%
inspection, while other methods require sampling and
lengthy electrical tests. With proper inspection of
materials used, soldering is the most reliable, time-
proved, and versatile form of electrical joining offering
the benefits of economy, dependability and speed.
A good solder joint will have the following recognizable
features: | |
a) Proper wetting - mixing of molecules to form a
singular, shiny bond of metal
b) Proper flow - feathering out of solder
c) Proper contour - outline of wire under solder
d) Proper fillet - solder filling in holes and crevices.
Because visual inspection is an important part of
recognizing a good solder joint, the following examples
have been provided to help with familiarization.
without any solder.
Fig. 7.3 Unsoldered Wire
Cause: Solder not applied.
Remedy: Correct amount of solder applied properly.
7-3
Problem: External strands.
Characteristics: One or more strands of wire outside terminal. This defect most common when cup-type terminals are
utilized.
ig. 7.4 External Strands
Cause: Poor assembly operation, too large diameter
Remedy: Correct diameter wire tinned prior to insertion.
wire used.
Problem: Cut strands.
Characteristics: Several strands of wire cut or broken and usually not soldered to terminal.
Fig. 7.5 Cut Strands
Cause: Improper wire stripping; wire flexed or bent Remedy: Use wire strippers similar to the one shown in
excessively during or after assembly. Fig. 7.6 . Care must be taken to avoid nicking or cutting.
Ig. 7.6 Wire Strippers
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Problem: Disturbed joint.
Characteristics: Rough appearance with questionable adhesion.
Fig. 7.7 Disturbed Joint
Use of holding vice or similar tool to help
Cause: Movement of wire/joint during cool-off stage. Remedy:
prevent movement.
Problem: Cold solder joint.
Characteristics: Joint with dull, frosty appearance;
often has poor adhesion as well as imperfect shaping.
Fig. 7.8 Cold Solder Joint
Cause: Too much heat applied (flux is boiled off before Remedy: Correct matching of iron/tip to specific job.
oxide removal action takes place). CUTE
| | Correct solder flux combination is also important.
Problem: Rosin joint.
TE
Characteristics: Joint 1$ separated by a thin coat of
flux producing high resistance to current.
Fig. 7.9 Rosin Joint
Cause: Solder applied previous to terminal reaching
minimum temperature (solder melting point).
When soldering individual component parts to printed
circuit boards, several procedures may be followed. The
following procedure complies to U.S. Government
standards and may be altered to suit a specific situtation.
|. Components leads should be bent to exact spacing of
mounting holes in PC board (Fig. 7.10) . This allows
leads to enter PC board at right angles and relieves stress.
Fig. 7.10 Component Lead Spacing
2. Leads should be bent down tight to pad.
3. Leads should be bent in the direction of the run
connected to the pad and clipped at a length
approximately %” (Fig. 7.11).
Fig. 7.11 Component Lead Bending
7-6
Remedy: Apply correct amount of heat; remove only
after good wetting and fillet is achieved.
4. Components should be held tight to the PC board
while clinching leads on other side (Fig. 7.12) and
soldered accordingly. Fig. 7.13 shows acceptable solder
joints.
Fig. 7.13 Acceptable Solder Joints
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When soldering to lugs (as on potentiometers), the
mechanical wire wrap should be a J hook with correct
insulation clearance as shown in Fig. 7.14.
Fig. 7.14 Soldering to a Lug
Turret terminals also utilize the “J” hook (Fig. 7.15).
Concentrate on good heat transfer to the terminal first,
then the wire. If two wires are to be soldered, be sure of
good solder flow to all three.
Fig. 7.15 Turret Terminal
Desoldering
In order to replace a component part, it 1s often necessary
to remove the old part by means of de-soldering. Several
methods are available, the most common being the
braided bare copper method. This wire is placed on the
lead(s) of the component to be removed with the iron
placed on top of the braided wire. This allows the solder
to heat up while simultaneously adhering to the braid.
When the braided wire is removed, the joint should be
clean. (See Fig. 7.16)
Fig. 7.16 Wire Braid Desoldering
Next, use points of small diagonals to lift ends of
component lead wires and remove the part. This
procedure is applicable to both PC board desoldering as
well as terminal and lug desoldering.
Note: Be sure that lifting of the component lead does not
also lift the copper foil pad from the board. Occasionally
a small amount of heat will be helpful.
Soldering is one of the most reliable methods of joining
electronic component parts and assemblies. When
properly used, it can be one of the most helpful tools in
service repair work.
7.4 Basic Troubleshooting
As is well known, time is an important factor in providing
efficient service repair. Therefore, several time-saving
troubleshooting steps are listed below. These hints may
or may not already be implemented in your service work.
If not, you may wish to experiment with them in order to
help improve your efficiency. After all, time is money!
A. Establishing Problems
User complaints about defective operation may not
always be clear or simple. Furthermore, the trouble the
user has experienced may be due to the system and not
the unit itself. If possible talk to the user about his
problem. This will usually be simpler than trying to
understand written complaints. À first hand account of
the problem can help in:
|) Getting the problem to re-occur on the service
bench.
2) Getting an understanding of the probable cause.
Some troubles will be obvious upon visual inspection.
When the trouble (or its symptoms) is not so obvious
ask: |
a) Exactly what was the problem; how was it
noticable?
b) How was the unit being used?
c) Has the system as a whole been caretully
examined for possible external problems?
d) How long had the unit been operating when the
problem occurred? Was it heat related?
If the user is unavailable or unable to explain the trouble
the next step is a thorough visual inspection.
B. Visual Inspection
A good visual inspection may often save hours of tedious
troubleshooting. Make a habit of proceeding in an
orderly manner to insure that no vital part of the
7-7
following procedure is omitted. The visual inspection can
be performed in 10 to 15 minutes. It is recommended both
as a preventive maintenance procedure and also for its
value in determining cause of malfunction.
1) Check that all external screws are tight and that
none are missing.
2) Check all fuses/ circuit breakers.
3) Check for smooth and proper operation of
switches, etc.
4) Inspect line cord for possible damage to cap, jacket
and conductors.
5) Remove protective covers as outlined in
disassembly instruction (Section 7.6).
6) Check that all attaching parts for internal circuits
are tight and that none are missing.
7) Inspect all wiring for charred insulation, or
discoloration as evidence of previous overheating.
8) Check that all electrical connections are secure.
This includes wire terminals, screw and stud type
terminals, and all soldered connections.
9) Check for obvious destruction of internal structural
parts. Distortion in any of these parts could mean that
the unit has been dropped or subjected to severe shock.
7.5 Discharging Instructions
The D-150A amplifier employs very large-storage
capacitors in the main power supply (C2, C3). For this
reason, at any time the covers are removed it is necessary
to discharge these large capacitors in order to avoid
possible damage to the unit and also to prevent shock
hazard. This is best performed by placing a 50 ohm/ 10
watt resistor across capacitor terminals shown in Fig.
7.17. Always use extreme caution while handling the
discharge device.
Fig. 7.17 D-150A Discharge Points
7-8
7.6 Disassembly for Inspection, Service,
Testing, Adjustment and Repair
The extent of disassembly required will depend upon the
extent of inspection, service, testing, adjustment and
repair to be performed. Illustrations referred to in
parenthesis (index numbers) are located in the parts list
(Section 6) of this manual.
The D-150A amplifier is specifically designed for easy
servicing. It may be partially disassembled and still be
made operational for bench testing and servicing. This
may be accomplished by removing the front panel,
transformer cover and wrap-around, and the board
electronics cover (Section A).
These steps provide easy access to nearly all major
components of the amplifier. Those that are not now
accessible for servicing can be removed following the
procedures given for replacing individual assemblies.
Caution: DO NOT attempt component replacement or
other repairs with power applied. Always follow
discharging instructions (Section 7.5) to prevent possible
circuit damage or serious shock.
A. Removal of Front Panel, Transformer Cover and
Wrap-Around, and Board Electronics Cover
1. Remove four socket head screws (7), two from each
end of the rack ears (6), and remove the six phillips
front panel mounting screws (30).
3. Remove two screws (15) from the top of the trans-
former cover (14), and remove the transformer cover
and the transformer wrap-around (13).
4. Remove two screws (33) from the top of the board
electronics cover (17) and remove the cover.
5. Reverse the above sequence of actions to reassemble
the amplifier covers.
B. Removal of Control Plate Assembly
|. Remove board electronics cover (17) as described
in paragraph À, Step 4.
2. Remove two screws (42) from top of control plate
assembly.
3. Carefully lift control plate assembly and turn nearest
edge (where screws were removed) upward until bottom
of control plate is accessible. Do not place unnecessary
strain on wiring connected to main PC board.
4. Input jacks (39) are now accessible for replacement.
C. Replacement of Components on Main PC Board
I. Remove board electronics cover (paragraph A, Step
4). Both component and solder sides of board are now
accessible. |
2. Carefully unsolder and replace (with identical parts)
any defective components.
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Caution: Use normal soldering precautions. DO
NOT use excessive heat; heatsink adjacent components
to prevent damage.
3. The IC is a plug-in component.
4. Resistors R128, R228 (selected bias resistors) are
plug-in components.
3. Disconnect four Faston connectors from terminals
of bridge DM-1 (66).
6. Reconnect four Faston connectors to terminals of
bridge DM-1.
7. Replace front panel (paragraph A, Step 2).
8. Replace transformer cover and transformer wrap-
around (paragraph A, Step 3).
D. Replacement of Input Level Potentiometers (R 105,
R205) G. Replacement of Filter Capacitors, C2 and C3
|. Remove board electronics cover, paragraph A, Step
4.
2. Remove front panel, paragraph A, Step 2.
3. Unsolder and tag for identification all leads to the
terminals of input level potentiometer (27).
4. Remove control nut (2) using a 4” nut driver and
remove defective R105 and R205 from the front panel
(5).
5. Solder leads removed in Step 3 to terminals of new
input level potentiometer (27).
6. Place new potentiometer in position and replace
control nut (2).
7. Replace the front panel.
8. Replace board electronics cover, paragraph A.
Replacement of Thermal Switch, SW-1
1. Remove front panel (paragraph A, Step 2).
2. Remove board electronics cover (paragraph A, Step
2). |
2. Remove board electronics cover (paragraph A, Ste
4).
3. Disconnect two Faston connectors from terminals
of thermal switch SW-1.
4. Remove two each, screws (51), hex nuts (45), star
washers (46), solder lugs (50) and remove thermal
switch SW-1 from the chassis.
5. Place new thermal switch SW-1 (49) in position and
replace hardware removed in Step 4.
6. Reconnect two Faston connectors to terminals of
new thermal switch SW-1.
7. Replace board electronics cover (paragraph A, Step
4).
8. Replace front panel (paragraph A, Step 2).
F. Replacement of Bridge, DM-1
|. Remove transformer cover and transformer wrap-
around (paragraph A, Step 3).
2. Remove front panel (paragraph A, step 2).
1. Remove front panel (paragraph A, Step 2).
2. Remove transformer cover and transformer wrap-
around (paragraph A, Step 3).
3. Remove one Faston connector from filter capacitor
(C2 or C3) terminal.
4. Remove two screws, (60), one solder lug (62), two
panel washers (65) and two fiber shoulder washers (64)
from the filter capacitor terminals.
5. Remove defective filter capacitor (C2 or C3) from
the chassis.
6. Place new filter capacitor in position and replace
hardware removed in Step 4.
7. Reconnect Faston connector to filter capacitor
terminals.
8. Replace transformer cover and transformer wrap-
around (paragraph A, Step 3).
9. Replace front panel (paragraph A, Step 2).
Replacement of Output Inductors, L101 and L201
1. Remove front panel (paragraph A, Step 2).
2. Remove board electronics cover (paragraph A, Step
4).
3. Unsolder one end of brown coil wire from the out-
put binding post terminal and the other end from the
adjacent driver transistor terminal. |
4. Remove hex nut (52), nylon washer (53) output coil
toroid core and brown wire (54).
5. Place new output coil toroid core and new brown
wire in position and replace hardware removed in Step
4.
6. Solder one end of brown coil wire to the output
binding post terminal (55) and the other end to the
adjacent driver transistor terminal.
7. Replace board electronics cover (paragraph A, Step
4).
8. Replace front panel (paragraph A, Step 2).
7-9
|.
Replacement of Driver and Output Transistors
|. Remove front panel (paragraph A, Step 2).
2. Remove board electronics cover (paragraph A, Step
4).
3. Unsolder and tag for identification all wires and
component leads connected to transistor terminals.
DO NOT unsolder leads attached to solder lugs mounted
on transistors.
4. Refer to detail drawings of output and driver transis-
tor and remove hardware shown and the defective
transistor.
5. Coat both sides of the insulator (86,91) between the
transistor case and the chassis with a heat-conducting
compound (Z5 silicon compound).
6. Install new transistor and tighten screws and hex
nuts snugly to assure good heatsinking.
7. Resolder wires and component leads removed from
transistor terminals in Step 3 above.
8. Replace board electronics cover (paragraph A, Step
4). |
9. Replace front panel (paragraph A, Step 2).
Replacement of Power Transformer, T-1
I. Remove front panel (paragraph A, Step 2).
2. Remove transformer cover (14) and transformer
wrap-around (13) (paragraph A, Step 3).
3. Disconnect seven transformer wires that pass through
the hole in the chassis beside the transformer base.
a. Two red wires; remove Faston connectors from
DMI terminals and remove Faston connectors from
the red wires.
b. One yellow wire; unsolder from solder lug (62)
at junction of capacitors C2 and C3. |
c. One black and one white wire; unsolder from
terminal strip (68).
d. One black/red wire and one black/white wire;
unsolder from terminal strip (68).
Input Signal
Type of Test/ Adjustment Characteristics
|. Quiescent DC offset None
2. Bias Adjustment None
3. Power Test (one channel driven)1 volt; 1K Hz
sine wave
7-10
4. Pull all wires back through hole in chassis.
5. Remove hardware securing transformer T1 to the
chassis:
a. Remove four hex nuts (70).
b. Remove four star washers (71).
c. Remove pilot light assembly (73, 74).
d. Remove terminal strip (68).
e. Remove rubber grommets (81).
f. Remove four transformer mounting screws (72).
6. Remove defective transformer T1 (75).
7. Cut leads on new transformer T1 to same length as
those on the transformer being replaced.
8. Place new transformer TI in position on the chassis
and replace, in reverse order, all item removed in Step
5.
9. Pull
bottom side of chassis.
10. Connect seven transformer wires to destinations
shown in Step 3 (also see Section 7.10).
I'l. Replace transformer cover and transformer wrap-
around (paragraph A, Step 3).
12. Replace front panel (paragraph A, Step 2).
7.7 Reassembly
Reassembly 1s essentially the reverse of disassembly. Ifin
doubt about types and sizes of attaching parts, refer to
the appropriate illustration in Section 6.
7.8 Electrical Checkout and Adjustment
Procedures
The following chart outlines an orderly checkout and
adjustment procedure for the D-I50A. The
equipment required to perform the various procedures is
listed in Section 7.2.
Comments
A. DC millivolt meter is connected to amplifier output.
Input level controls are fully counterclockwise while off-
set controls (R105, R205) are ‘adjusted for zero volts at
output. |
В. Input level controls are at twelve o'clock (or ajusted
for maximum DC offset). Offset controls (R 103, R203)
are adjusted for zero volts at output.
Positive output, base-emitter junction should be between
.3V and .35V. It is altered by selected resistors R128,
R228; they are typically between 92 and 240 ohms.
Into 8 ohms, 28Vrms (98 watts) should be obtainable.
before signal clip. Into 4 ohms, 26.5 Vrms (175 watts)
should be obtainable before signal clip.
all transformer wires through chassis hole to
Crow
4. Protection Circuitry | volt; LKHz Into 2 ohms, 39Vrms should be obtainable before signal
sine wave clip without a load.
5. High Frequency | volt; TOK Hz Into an 8 ohm load, a 30 volt peak-peak square wave
square wave signal should exhibit no ringing.
| volt; 20K Hz Into an 8 ohm load, a 27Vrms signal should exhibit no
sine wave ringing.
6. Intermodulation Distortion .5V £2%: 60Hz- — (See Fig. 7.18) When using the Crown IMA, typical
7K Hz signal readings will be as follows:
summed in 4:1 0dB = .0049% (20 volts out)
ratio through -25dB = .01%
through -40dB = .03%
Note: All distortion readings must be below .01;.
7. TOC 2.5V peak-peak ¡OC lights should illuminate once for every rise time and
.5Hz square wave once for every fall time (twice every full cycle). Test
generator rise time must be less than 1.0 microsecond.
8. Signal to Noise (See Fig. 7.19) Signal to Noise should be 115dB below
rated output with meter bandwidth of 20Hz to 20K Hz.
9. Quiescent AC Power 30 watts at idle as monitored by wattmeter on AC line:
250 watts full rated output.
(100 MICROVOLT SCALE) |
a
AC VOLTMETER 7 |
20-20 KHz RETURN UNGROUNDED- WRAPPED AROUND OUTPUT CABLE
LOW NOISE |
FILTER
D-150 A
EITHER
(LEVEL CONTROLS; MINIMUM ) re | CHANNEL
(INPUTS DISCONNECTED) = ое
OUTPUT
EITHER OUTPUT
CHANNEL
Fig. 7.18 IM Distortion Test Set-up
7-11
AC | SIGNAL | DIGITAL |
sioner | [outers | GENER ATOR COUNTER |
| 20-20 KHz |
| LOW NOISE
| FILTER
| POWER |!
| SUPPLY |
MONITOR |
| & VARIAC |
EITHER
CHANNEL
D-150A
AMPLIFIER
Fig. 7.19 Signal to Noise Test Set-up
7.9 Troubleshooting Hints
Symptom Defect
Blows Fuse |. Rectifier block shorted, DM 1
2. CI shorted
3. Leaky or shorted filter capacitors C2, C3
4. Bootstrap supply AC wire frayed and shorts to
positive supply trace on Main Board
Shorted power transformer TI
A shorted power device in both positive and negative
output stage QI110, QI114, Q210, Q214
7. Fuse blown due to external problem - wrong size fuse
inserted
>
8. Pinched wires in power supply
No Output Stage Bias |. No bias resistor R128, R228
2. Bias resistor connector to circuit board not soldered
3. L100, L200 open
4. C-E short of bias transistor Q111, Q211
High Bias (amplifier heats up) I. Amplifier instability-high frequency oscillation
(check Q106, Q206)
2. Shorted output terminal post
DC offset (see offset section)
4. Leaky output device (may pass signal and show okay
with continuity test) Q110, Q114, Q210, Q214
‘о
7-12
Symptom
Negative Offset
-Both Channels-
Positive Offset
-Both Channels-
Positive Offset
-Single Channel-
Negative Offset
-Single Channel-
Small DC Offsets
Negative half of Signal missing
Positive half of Signal missing
Oscillation (Full waveform)
Oscillation (Positive half)
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Defect
Defective IC op amp (UA739)
DS shorted
QI101, Q201 leaky or shorted
Defective IC op amp (UA739)
D4 shorted
Defective 1C op amp (UA739)
Q100, Q200 leaky or shorted
QI01, Q201 open
Q106, Q206 open, leaky or shorted
Q105, Q205 open leaky or shorted
Positive predriver, driver or output device leaky or
shorted Q107, Q207, Q109, Q209, Q110, Q210
Q111, Q211 shorted
Defective 1C op amp (UA739)
Mono switch hot wire shorted to ground
Negative predriver, driver or output device leaky or
shorted О112, Q212, Q113, Q213, Q114, Q214
О101, Q201 base to collector leakage
Broken ground on input level control (R105, R205)
Input jack hot lead and ground pin not shorted
together (level controls full up with no input jack)
D100, D200 leaky or shorted
Q112, Q212 open
Violet/ white wire from main board to output board
open or not soldered
Bootstrap supply
a. C4 open
b. DI! or D2 shorted
c. Green AC wire not soldered correctly
QI101, Q202 open
Loss of positive supply voltage (+45V)
D3 shorted
Q108, Q208 open, leaky or shorted
Q107, Q207 open
R132, R232 open
Yellow/ white wire from main board to output
board open or not correctly soldered
R106, R206 open
C116, C216 open
Defective IC op amp (UA739)
Defective driver, Q109, Q209
C113, C213 open
7-13
Symptom
Oscillation (Negative half)
Protection Circuit - No current limiting
-Excessive limiting
-Current limiting oscillation-
-Flyback pulses from inductive loads -
Clipping (negative) Both Channels
Clipping (positive) Both Channels
Clipping (positive) Single Channel
Clipping (negative) Single Channel
High IM (Load Related)
Low dB IM
7-14
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Defect
Defective 1C op amp (UA739)
C112, C212 defective
Defective driver, Q113, Q213
Current limiting transistor open
a. Positive (Q103, Q203)
b. negative (Q104, Q204)
D101, D107, D201, D207 open
R119, R118, R219, R218 open
C108, C109, C208, C209 open
D101, D107, D201, D207 shorted
Q104, Q103, Q204, Q203 shorted
Loose output hardware
Negative feedback capacitor, in limiting transistor
circuit defective, positive C107, C207, negative C110,
C210
C108, C109, C208, C209 open
D5 leaky or open
Q2 leaky or open
Defective IC op amp (UA739)
D4 open or leaky
D3 open or leaky
Defective IC op amp (UA739)
D1 or D2 open (positive portion of signal will clip at
a 60Hz rate)
C4 open or changed in value
Open or leaky predriver, Q107, Q207
Shorted or leaky limiting transistor О103, Q203
Open output emitter resistor R132, R232 |
Defective IC op amp (UA 739)
Q102, Q202 defective
Open or leaky predriver Q112, Q212
Shorted or leaky limiting transistor Q104, Q204
L100, L200 open
Open output emitter resistor R134, R234
Q115, Q116, Q215, Q216 on IOC board defective
R9 (1 ohm) open
Defective IC op amp (UA739)
C101, C201 open
С114, C214 open
Q106, Q206 defective
Defective predriver or driver device Q107, Q207,
Q112, Q212, Q109, Q209, Q113, Q213
Low output Bias
‚ С102, C202 open
C104, C204 open
crown
Symptom Defect
High IM (Not Load Related) |. R115, R215 changed in value
2. R109, R209 changed in value
3. C105, C205 changed in value
4. C106, C206 changed in value
120Hz in output waveform 1. Power Supply filter capacitor(s) open, C2, C3
2. C5 open
3. Power Supply filter capacitor mounting hardware
loose
High noise 1. Input jacks not isolated from chassis ground
2. Noisy zener diode, D3
3. Broken ground on input jack, in input cable or on
input level control (R105, R205)
4. Oscillation (C101, C201 open)
7.10 Voltage Conversion Instructions
Often Crown products are purchased in one country and E Е El |:
later transported to another requiring an AC mains 100v Г |
conversion. For this reason the following AJ LI IS Pel
chart/explanation as well as a world-wide voltage map x © |
(in the rear of this manual) is provided. SÉ IP
3 3 [a2
The D-150A power supply may be connected for any of 1200 | |
five voltages. Converting from one to another can be В Це
accomplished with a soldering iron and a pair of wire
strippers. Observe the following instructions: Z
1. Remove the two rack ears from the front panel. =
200
2. Remove the front panel/ bottom cover (See Section AU bel
7.6A). a
Tia |»
za la
3. Position the front panel to gain access to the \
transformer leads. Locate the two terminal strips 200 OO
(terminals A,B,C, D and E).
=
a ©
4. Determine the correct connection from Fig. 7.20 and T $ Tx
solder the leads accordingly. al ie
240V
5. For all connections 200VAC and above, the line fuse La] LJ le le)
F1 is changed from 6.25 amps to 3 amps.
6. Carefully check all connections, then repeat steps |
and 2 in reverse.
Fig. 7.20 Voltage Conversion
7-15
7.11 Block Diagram Circuit Theory
The following discussion refers to the block diagram in
Fig. 7.21.
The input amplifier is the initial stage of circuitry that
establishes the fixed gain of the D-150A. The input bias
compensation stage, directly related to the input stage,
helps control any DC drift that may occur with a unique
temperature-controlled circuit.
The IOC (Input Output Comparator) circuitry works in
conjunction with the error correcting signal of the main
op amp. Any time a small “non-linearitv” exists in the
amplifier, an error signal appears at the output of the
main op amp (via the fedback loop of the unit). This
produces an abnormally high value, exceeding the
“window” of the IOC and illuminating the LED. Since
transient overload can happen rapidly, a pulse stretching
circuit is added so the eye can detect the LED lighting.
The signal translator stage combined with the last voltage
amp form the voltage amplification stages of the D-150 A.
Virtually no voltage amplification is performed beyond
these stages.
Current amplification circuitry consists of basically three
stages: the Predriver, the Driver and the output
transistor stage. Connected to these stages, is the
protection circuitry which is activated when a
predetermined amount of voltage and/or current is
drawn across the output stage sense resistors. This
protection signal is then in turn fed back to the limiting
circuit which limits any increase in the bias servo voltage
to the power devices.
The power supply is a continuous-duty type. The main
DC supplies are full-wave capacitor input type with
heavy duty, chassis heat-sinked diodes. The input
amplifiers are powered by zener-regulated power
supplies. The bias regulators are also powered by zener-
regulated current sources with the result that line voltage
variations do not cause noise or distortion due to mis-
biasing.
INPUT
COMPENSATION N FOSITIVE POSITIVE
> DRIVER | OUTPUT
STAGE STAGE
a
: ]
- LAST
INPUT SIGNAL №. BIAS PROTECTION
AMP | TRANSLATOR VOLTAGE SERVO CIRCUIT
CH.1 af,
INPUT | | T4
ie ;
NEGATIVE NEGATIVE
DRIVER >> OUTPUT
STAGE STAGE
INPUT
OUTPUT
COMPARATOR
CH.10UT
$ 10K / r
>
$ --d
§
Co | ¡MONO
L - - | =
= ST. 7 MONO --Q
LS
CH.20UT
INPUT
IAS :
POSITIVE POSITIVE
COMPENSATION > ORIVER > OUTPUT
STAGE STAGE
4
, |
ao E > | 7
INPUT e SIGNAL __ > VOLTAGE BIAS PROTECTION L — |
CH. 2 AMP TRANSLATOR AMP SERVO CIRCUIT
INPUT” +
Рот PL x j 4
| NEGATIVE N NEGATIVE
1 era DRIVER OUTPUT
|
INPUT
STAGE STAGE
QUTPUT
COMPARATOR
Fig. 7.21 D-150A Block Diagram
7-16
crown
7.12 Theory of Operation |
The following explanation refers to schematic diagram
MI-261E located in Section 6. However, each circuit
under discussion is reprinted below in order to aid in
circuit familiarization. Only channel 1 is shown for
simplicity.
A. Input Stage
After entering the unbalanced 7” input jack, the input
signal level is adjusted to a desired input amplitude
through RI0S and then applied to the dual IC
operational amplifier (IC1A, IC1B). Thisopampisa low
noise, large gain bandwidth type which results in usage of
feedback cirucit loops throughout and ultimately,
extremely low distortion values. The direct input signal is
applied to the non inverting input (pin 5) of ICI A and the
feedback signal is applied to the inverting input (pin 6).
Both signals entering СТА will be in phase with each
other because of the feedback path and will thus produce
an output (pin 1) of almost zero. The IC op amp will
always try to keep a zero potential difference between
both inputs. Any type of non-linearity will cause the op
amp to produce a large output, and therefore a
substantial size correction signal in order to rétain the
small output level.
HOV
©
IRPUT/OBFSET ||
dai
== D4 Rig? > R102
55 > pao 250K LOG q
= > 4 I
css Do
SS ser = @100 р |
<
<
4 R137 ¢
© RIM 1808 <
< IK
ый
1.750
las C108
TT ar ;
A108 <
SEE NOTE < S ouTPUT
| OFFSET
=m SR Ee SER Ee SE cof AE AS
An
Fig. 7.22 Input Stage
B. Voltage Amplification
The operation of the D-150A front-end circuitry (IC op
amp through QI05) is to basically provide voltage
amplification. However, the signal translator transistor
(Q101) provides no voltage amplification itself, but
rather converts the ground referenced input signal to a
signal with a reference to the negative supply (-45V). The
result is higher voltage swing capabilities from QI05
(final voltage amplifier).
The final voltage amplification transistor (Q105) is the
main source of voltage amplification in the D-150A.
R116 in the base circuit of this transistor serves two
purposes:
01 |
|) it provides collector current for О101
2) it allows the signal on the collector of QIOI.
to be developed across it and thus amplified.
As this development is in process, Q105 emitter voltage is
developed across R124. When this voltage reaches a
positive .6V, Q106 turns on and “pulls” the drive away
from the last voltage amplifier, thus acting as a current
limiter for Q105.
Rí07 i <
se < 8108
$ An
cos
<
< Rig
© IK
ow
wine C104
= arr
R115
к > se C185 R108
* > e 120PF 510
y Y > 1%
§ a D }
wes СТОБ
= 00PF
a105 © AAA
al ati
18K
1%
$
€ nié
aies | 2 ga
<
Ris < ae
31 < 9 —
} | |
“ой
Voltage Amplification Stage
7-17
crown
SECTION 8
SERVICE BULLETINS
Periodically, a situation may arise where Crown will feel
that it is necessary to change or update specific circuitry
by the addition or subtraction of component parts. This
information is automatically sent to all Crown Warranty
Service Stations. It should be kept with this manual,
preferably behind this page as indicated by the note at
bottom. Should there be any question pertaining to these
changes or updates, call or write the Crown Technical
Service Department.
PLACE ALL
SERVICE UPDATES
HERE
8-1
— 4
THERMAL T ey
SWITCH
ORN BLKWHT JP 00
— юг me
| +] |
INTERNAL FUSE F2 YEL | a ca
| | R10 10/160v D2
| AA A М в! +100V
LINE FUSE | 1 nm,
| ; > C5
F1 RED + A = | R110 D1 22e SF mov R210
L + 24K Î +70V 2.4K
7 == 6400/50v | — MM — A AAA
BLK
—\ AJ | | a D3
= RED 0102 0202
GAN + 45V 4— e + — + 45
= WHT rh 1 ™
<
7 mM aa ств | $ 25 2°
hal T + 1.45v p Pw N + 1.450
= —— $
POWER SUPPLY SHOWN WIRED FOR 120VAC LINE, = YELMHT
R4
En — m 33VAC 0709 Une Y D102 200K $ $ Nk x D202
< Te <a — - i VAA sv A a. он
0110 > 7 | эк J с?
D103 100/12v D203
a103 0203
Г + .34v | ‘ RY. N—4 >t 4 ) +—k e Т q р id 4 В
BTAS SETTING ; R117 4 = R217 5% > BIAS SETTING
111” | mS Tw m3 FW $ г HT La | | A gh "| |
BRN/WHT A 5% Sk + | | A ho | BRN/WHT
NA A N— €
| R118 = = C208 R218
| + Pre om м | E
> R132 | в № 5.6K +10V sex | p 5%.
RED E + 45V > 1 | pe —————— | || , FAN a И a dm — AA ii | : > R232
THERMAL Ti > SW < R125 ` € :
SWITCH > R120 _ и OFFSET INPUT OFFSET * R220 $ Ras > BW R233
ORN BLK/WHT 27" | 00 3 ге | ca Y ows oF oe 4 5107 > es = R202 } R207 R213 0205 Ÿ six $ ME 0.000 27
— e men 0.00v 1w > R106 260K LOG 250K LO R208 < 8.2K 1w г , BAN
RED + AA = in ата Nee eed) » ou X + 2.350 AN S a ¢ эк © в УФ 2,350 К D204 ¢ bean Nem = AA
| R121 R113 c200 R221 |
| = SL 00/50 | ena = 7 Y pro 25/18 BH == er = 0100 | 0200 = 0208 == 26/16v Ds Y a => ca13
NP ;
INTERNAL FUSE F2 YEL L101 5% R201 = L201
| ‘ [0 N | 3UHY | il AN il pr $ Ато! M $ || AAA il | JUHY —
<
| = oe Зо Yo | me 82 | gq w 7 EE wm | Wow m3 mt
LINE FUSE | — A $ Bw 120 5% $ > 175 | 175 M $ 5% 120 WS
RED + 1.75 + 1.75
FI — = À J cm TU NAN Q101 Ч. TS его! A | == |
L_ M сз = “01 $ he Too cmo c210 ol cz подв = CHANNEL?
x == 9400/50V CHANNEL 1 > == со LÀ co R100 A200 001 == = 0022 < 780 OUTPUT
MN He NM Nn A| [x | To" y | 100k Sa cm A 44 MN nN / me |
À SRN ] $ 29 > 3 L100 ated SEE NOTE $ 4 $ Y sEENOTE TPF T 0204 { 4 |
RI 128 R127 > >. >
" , 35" SEP 307 Jun | my | TS ame Su y Iw Sa pe
À w | — |
LA b> - 45V = | q ore .004v
POWER SUPPLY SHOWN WIRED FOR 240VAC LINE. ) . и
EE 33VAC | == Ne | |
| YOK > - C205 < R216
% 2 T ТОРЕ 510” 120PF == > 1%
Li я
NOTES: lee AD § 3m, Jl |
anz 64v 4 = Ww = - 64v
- THIS SCHEMATIC APPLIES TO AMPLIFIERS NUMBERED jp € == co or == €
SN8359 TO SN17875 (SELECTED UNITS). wont Lou va _ —|
>
- DC VOLTAGES ARE SHOWN FOR VARIOUS POINTS. THESE | + 1 ет» Г | |: mm
= 4 4
ARE THE NORMAL OPERATING VOLTAGES FOR ZERO air ss | as | 3 200 — — | ||
R136 Î , + }
INPUT. | < os | 310 #124 $ a = — . Iv Г $ Raa Зи
5W w + 4
- THE HEAVY CONTINUOUS TRACE FOLLOWS THE PRIMARY = 45V +— ¿ —d y ) A AH Mm 4 1 > gy
SIGNAL PATH THROUGH THE CIRCUIT. THE HEAVY | |.
BROKEN TRACE SHOWS FEEDBACK PATHS.
- WIRE COLOR CODES ARE GIVEN FOR THE MAIN POWER
SUPPLY AND SOME BOARD WIRES.
- ALL RESISTORS IN OHMS UNLESS OTHERWISE STATED.
- ALL CAPACITORS IN MICRO-FARADS UNLESS OTHER-
WISE STATED.
- COMPONENTS COMMON TO BOTH CHANNELS ARE
NUMBERED FROM 1 TO 99.
- CHANNEL ONE COMPONENTS ARE NUMBERED FROM 100
TO 199.
- CHANNEL TWO COMPONENTS ARE NUMBERED FROM 200
TO 299.
- FOR MONO CONVERSION TIE POINT A TO B AND C TOD.
- R108 AND R208 SHOULD BE 3.3K, WW WHEN IC! IS NA749.
Fig. 6.1 M1-261 Main Board Schematic
l—
CHANNEL 1
INPUT
R105
25K LOG
—ojos i — ——— _——]]Ál-——]] ]———]]—. —— "===" i—Ñ]]]ÑÚ
He
R205 < CHANNEL 2
26K LOG
* THERM. COUPLED TO
HEAT SINK
cron oso
Laboratory Power Amplifier
MI 261
NPC OUTPUTS
ia
390 —
5
Ce | о
MON TO NELS NUM
VN
R108, 208 ARE OMITTED WHEN IC-1 1S uA739; 3.3K WHEN
uA749 IS USED.
Fig. 6.2 MI-261 Foil Board Layout
Bl
THERMAL T1 vu + 46V
SWITCH
ORN BLKAWHT PP 0
| ee, а RED г 3svac
|| I a
| TT" 9400/50V
INTERNAL FUSE F2 YEL | J
‹ i = el R10 10/150V D2
| Í ' a AA KH „а +100V
| | Y YY И + vi
LINE FUSE — 1 Ф в tl CS
Fi RED | o ; = R110 & 0 2x TT 10/50v R210
| 4K
L ай em сю ен ным — 4 + |. cs . AAA TN +70V ZN. AA
== 8400/50 |
BLK x Da
; SN ST
— ‘ RED 102 0202
— GRN A +45V + + + = + — + 46V
<
— WHT 7 4 BLU cus 1 $ 53, eas
a -usy ; T + 1.450 p PW + 1.45v
= mi bh JM —
POWER SUPPLY SHOWN WIRED FOR 120VAC LINE. R4
a108 Y D102 200K $ < o Y ox T
TH 3IVAC Ч x 1 1 +sv a
= = —Ñ ANA E — И
— m
ano эк de C7
D103 atos J T 100/1724 0203 D203 :
+ ‚у ‹ К a в — | .
BIAS SETTING | Qn Ca > C107 | 4 = с217 | | c207 Sn e 3 BIAS SETTING
BANMWHT A | sm | 58K $ | 1 | 5% | | BRN/WHT
R118 R119 > C108 = = c208 > R219 R218
| | = 82 < НЫ R112 R212 | da 2 2 oe
< 6.6K 5.6
RED + “sy $ haz | tr ) | AAA +10У И 2 ae y AY || | —— S R232
oui EW < $ A
SWITGH n ho $ 220 I ER Y 0105 св == ыы я” во) J INPUT OFFSET INPUT OFFSET 0208 Y R220 > #25 $ EN R233
ORN BLK/WHT y 1/2NMF 5% a T > R202 : R207 nas q © 12wme 27
| — Xr + RED Mn nn == A = J WW |] © 2 a N 250K LOG 8.2¢ Ww | > 0.00v BAN zw
; py ГУТ D104 2.35 AAA Ро AA * 2.35 2 D204 or] = 26. Ann |
| | | 8121 X C109 ana 103 | Bons у coo К | en | AN
+ — - — = — iaa
| =F Shor o E | Be T= = m A к | Отв wr | А = a аи
INTERNAL FUSE F2 YEL | 3UHY o it 1 Jl A Il ЗОНУ
| { — Ci Y Y | = 2M « N Y Il
| I 7 | A122 4 > <
cm rss | | ih You | me E | 3 ‘ w $ SE? ве ¥ oo ms qe
F1 RED EA I 1 T | Ч % > La 1 + 1.75v À + 1.750 La! > 5% 5% A | >
Va 4 = > — —— AN 0101 0201 AA dé —k Lo
' 1 $ cH12 ey r A ™~ VV "azi
L i < 8128 =
= р — == == — == — - toc снАММЕС — < 760 p 0022 = C110 сго dn aden C212 2 R226 = CHANNEL 2
BLK = 9400/50V OUTPUT Г 001 + c104 R100 R200 | 001 == T= 0022 < 760 OUTPUT
== Ра НИ Mu MM sf (I d m 47PF р101 100K D201 À x Mn
= sem € ww E J DU Emo = dd Tw | —T—
GRN R129 R128 > R127 L100 > > >
WHT 7 Z se. 2 5MHY Dos Y | f ore 2— Y 020 . L200 $ ma;
{7 A BLU mM [ m= our | 820K
- pte - 45у .004v .004v
POWER SUPPLY SHOWN WIRED FOR 240VAC LINE. | mM / N =v
e 33VAC 1 |
+ D5
RUG Ш = R209 «
ET Y mE 35
LP) q 1% < 1% S 1%
| D ) $ ox “В” 1 A |
NOTES: an | | + Зы = {| | us
€ == oo sor €
- THIS SCHEMATIC APPLIES TO AMPLIFIERS NUMBERED Lon J | E И coa
= 200PF = — 200PF
SN8359 TO SN17875 (SELECTED UNITS). й И | L
1 C211
= 470PF 470PF
- DC VOLTAGES ARE SHOWN FOR VARIOUS POINTS. THESE a 4 ve | $ те не $ | ого я
. < 820 « It
ARE THE NORMAL OPERATING VOLTAGES FOR ZERO f $ tf 1 ‘
R124 € 9 > R224
INPUT. +70 ва < + = e 2 82 „310
= 45V #+— y + } mM Ча A N y + } > — av
- THE HEAVY CONTINUOUS TRACE FOLLOWS THE PRIMARY q
SIGNAL PATH THROUGH THE CIRCUIT. THE HEAVY |
BROKEN TRACE SHOWS FEEDBACK PATHS. nn lA e > —— o _— | _ —]
- WIRE COLOR CODES ARE GIVEN FOR THE MAIN POWER | > 27 Roses
SUPPLY AND SOME BOARD WIRES. +
- ALL RESISTORS IN OHMS UNLESS OTHERWISE STATED. Fig. 6.3 MI-261A Main Board Schematic
- ALL CAPACITORS IN MICRO-FARADS UNLESS OTHER- | — A y A AM Crown o/s
WISE STATED. | e hoo = super?
- COMPONENTS COMMON TO BOTH CHANNELS ARE Laboratory Power Amplifier
NUMBERED FROM 1 TO 99.
- CHANNEL ONE COMPONENTS ARE NUMBERED FROM 100 MI 261A
TO 199. | FAIRCHILD OUTPUTS
- CHANNEL TWO COMPONENTS ARE NUMBERED FROM 200
TO 299.
- FOR MONO CONVERSION TIE POINT A TO B ANDCTOD.
- R108 AND R208 SHOULD BE 3.3K, :W WHEN ICI IS NA749.
He
0 BOTH CHANNELS NUMB
&
A м @ | ©
LEFT CHANNEL ONLY: RIGH
SUN E | 8 WN a
R108, 208 ARE OMITTED WHEN IC-1 1S uA739; 3.3K WHEN
uA749 IS USED.
Fig. 6.4 MI-261A Foil Board Layout