1800-A VTVM, Manual
OPERATING AND MAINTENANCE
INSTRUCTIONS
FOR
TYPE 1800-A
VACUUM-TUBE VOLTMETER
FORM 653-D
. GENERAL RADIO COMPANY
""'CAMBRIDGE
39, MASSACHUSETTS
TABLE OF CONTENTS
INTRODUCTION .
SECTION l.o-DPERATING CONTROLS AND
PROCEDURE
1.1
Instrument Support
1.2 Mechanical Zero
1.3 Power Supply
2
1.4 Electrical Zero .
2
1.5 D-C Voltage Measurements
3
1.6 A-C Voltage Measurements
4
5
SECTION 2.o-CIRCUIT AND CONSTRUCTION
2.1 General Construction .
5
2.2 Probe
5
2.3 Probe Fittings
6
2.4 D-C Amplifier
6
2.5
Indicating Meter
7
.
7
2.6 Zero Controls
2.7 Degeneration
7
2.8 Power-Supply Stabilization
7
2.9 Reconnecting Power Transformer for Different Line Voltage
7
SECTION 3.o-OPERATING CHARACTERISTICS
8
SERVICE AND MAINTENANCE NOTES
10
VACUUM..TUBE DATA .
15
PARTS LIST .
. 16
WIRING DIAGRAM
.
Price 50 cents
• 18
OPERATING AND MAINTENANCE
INSTRUCTIONS
FOR
TYPE 1800-A
VACUUM-TUBE VOLTMETER
FORM
653-D
GENERAL RADIO COMPANY
CAMBRIDGE
NEW
YORK
39,
MASSACHUSETTS
CHICAGO
U.
S.
A.
LOS ANGELES
Figure 1. Panel view of the Type 18oo-A Vacuum-Tube Vollmtter (left) with handle in vertical carrying position, and (right) with
the handle loclt.td in position for supporting instrument with inclined panel.
OPERATING AND MAINTENANCE
INSTRUCTIONS
FOR
TYPE 1800-A VACUUM-TUBE VOLTMETER
INTRODUCTION
The Type 1800-A Vacuum-Tube Voltmeter is a high-impedance voltmeter
incorporating both a-c and d-e ranges for voltages up to 150 volts. The upper
frequency limit of the a-c ranges is in the vicinity of 500 Me.
On the a-c voltage ranges, except for the two lowest, it is essentially a peakreading instrument, but the scales are calibrated to give readings of the r-m-s
alue of sinusoidal applied voltages.
The circuit is shown in elementary form in the Elementary Schematic Diagram, Figure 2. A complete circuit diagram is shown in Figure 7, at the back
of this book.
Mechanically the voltmeter is small, compact, and convenient to use, while
the chassis construction makes all component parts easily available for servicing.
SECTION 1.0
OPERATING CONTROLS AND PROCEDURE
1.1 INSTRUMENT SUPPORT
The walnut cabinet is provided with a handle that can be used to support
the instrument in an inclined position. The handle locks into position for
carrying the instrument and into the support position. Figure 1 shows the
handle in the two positions. It is released by pressing in on the handle near
each hub.
1.2 MECHANICAL ZERO
Before turning on the power, check and reset if necessary the mechanical
zero on the meter.
1.3 POWER SUPPLY
Be sure that the line voltage and frequency correspond to those on the plate
under the power input socket. The power transformer primaries can be connected for either 115-volt or 230-volt operation. Section 2.9 details the changes
in connections for converting from one voltage to the other. The plate indicates the voltage for which the instrument was connected when shipped. If
changes are made, the plate should be reversed. One side is stamped for 11 5
volts, the other for 230 volts.
1.31 Connect the instrument to thea-cline with the cord and plug assembly provided.
1.4 ELECTRICAL ZERO
Fasten the connecting link across the OPEN GRID D-C terminals. Turn
the OFF-A.C.-D.C. switch to D.C. and allow the instrument to warm up for
about five minutes. Turn the VOLTAGE RANGE switch to 0.5 and adjust
the meter reading to zero with the panel ZERO control. Turn the OFF-A.C.D.C. switch to A.C. Short-circuit the HIGH and LOW A-C terminals. The
meter reading should be approximately zero.
1.41 It is likely that over a period of time the a-c zero will drift out of
exact coincidence with the d-e zero. If this happens, the coincidence can be
restored by adjustment of the A-C ZERO adjustment, or the meter reading
may be set to zero by means of the panel ZERO control. In the latter case the
d-e and .a-c zeros will not coincide. This causes no harm beyond the inconvenience involved. (See also Section 2.6).
1.42 The panel ZERO control may be centered if necessary by use of the
COARSE ZERO adjustment on the bottom of the chassis.
1.43 If the OPEN GRID D-C terminals are used and the 10 MEG n
terminals short-circuited, the zero can not be adjusted unless the voltage source
is connected to the terminals with the voltage at zero, or unless a resistance,
which for high accuracy should be equal to the voltage source resistance, is
connected to the terminals.
1800-A ELEMENTARY .SCHtMAI!C DIA6RAM
Figure
2.
Schematic diagram of Type r8oo-A Vacuum-Tube Voltmeter.
2
1.5 D-C VOLTAGE MEASUREMENTS
1.51 Polarity-In the case where the negative side of the voltage being
measured is grounded, be sure that the LOW A-C terminal is not connected
to the ground terminal, G._ The +D-C terminal and the LOW A-C terminal
are common.
1.52 Ground-It is usually desirable to ground the panel at G.
1.53 Range Switch-Set RANGE switch to desired full-scale value.
1.54 Input Resistance-For d-e voltage measurements, two values of input
resistance, l 0 MEG Q and OPEN GRID are provided. A link is provided
to short-circuit the resistance that is not used.
The OPEN-GRID resistance is determined by the insulation resistance and
by the flow of grid current through the voltage source. The resistance caused
by the flow of grid current varies with the voltage being measured:
E
R=Iu
where Iu = 1. 5 X l 0-9 amp. or less
E = voltage being measured
R = input resistance because of I 0
1.55 Zero Reading-The zero reading depends upon the value of the
source resistance of the voltage being measured, for grid current from the d-e
amplifier tube, V-3, flows through whatever resistance is across the input
terminals. In order to obtain highest accuracy the zero should be adjusted
with a resistance that is equal to the source resistance placed across the input
terminals.
1.56 Adjustment for Minimum Error-If the parallel combination of
source resistance and input resistance does not differ by more than l megohm
from the resistance across the terminals when the zero is adjusted, the error
caused by change in zero when the source is connected to the terminals will
not exceed 0.5% of the full-scale reading on the 0.5-volt range.
If the VOLTAGE RANGE switch is turned to the 0. 5-volt position immediately after the instrument has been used to measure a high voltage, the
meter pointer may be somewhat slow in returning to zero. Although the
lumped capacitance values were chosen to give a low time constant, interfacial
polarization in the dielectrics of the distributed capacitances of the probe,
cable, and associated circuits causes the charge stored in these distributed
capacitances to decay slowly. As the discharge takes place through the high
resistances in the probe, this slow decay makes the meter pointer drop slowly.
The effect becomes most noticeable as the discharge, and therefore the meter
pointer, nears zero.
3
GENERAL RADIO COMPANY
1.57 Correction-When the source resistance is high, correction should be
made for the voltage-dividing effect of the input resistance. The true source
voltage may be obtained from
t;
_
"--aouree -
t;
1..1ndlcated
X Rsouree
o
+ Rtnpu&
l'lnput
1.6 A-C VOLTAGE MEASUREMENTS
1.61 Probe-A-C voltages to be measured may be applied either directly
to the probe terminals or to the panel A-C terminals with the probe plugged
into position in the compartment at the top of the cabinet. When the panel
input terminals are used, the capacitance loading and the frequency error are
greater than when the voltage is applied directly to the probe. &cause of this,
it is advisable to connect directly to the probe when measuring high-frequency
voltages.
The probe may be used with or without the end cap. The input capacitance
is about I JJJ.If lower when the cap is off. When the cap is on the probe, the
terminals provided are either the GR Type 274 Plug Terminals or the GR
Type 774 Coaxial Terminals. A 50-ohm terminating resistor is supplied for
use with the Type 774 terminals. For high-frequency measurements where a
minimum-induct.ance connection is desired, the cap may be fastened to a flat
ground plate that has a hole giving access to the high terminal.
1.62 Polarity and Grounding~lf the a-c voltage being measured is at
some d-e potential above ground, the LOW A-C terminal should be disconnected from the G terminal.
It is usually advisable to ground the panel at G.
Fiture J· Exploded view of the
voltmeter probe including Type
.1.74 anJ Type 774 terminations
and JD-ohm terminating resistor.
4
TYPE 1800-A VACUUM-TUBE VOLTMETER
1.63 D-C Potential- The maximum d-e voltages which may be applied
across the probe terminals are: positive polarity to HIGH terminal, 300 volts;
negative polarity to HIGH terminal, 700 volts.
The maximum d-e voltage which may be applied from the LOW A-C
terminal to ground is 500 volts.
1.64 A-C Meter Scales-The two outer scales, which are linear, are used
both for d-e voltages and for a-c voltages greater than 5 volts. The three nonlinear inner scales are used only for a-c voltage measurements.
A mirror has beer. ;".::,ated between the inner and outer groups of scales.
he mirror does not increase the accuracy of the instrument, but it does make
it possible to read the voltage more precisely. The extra precision of reading or
setting is especially important when small differences must be observed. The
upper portion of the pointer has been made knife-edged to facilitate further
the precise observation of small differences. The lower portion has been made
broad so that the approximate position of the pointer can be seen from some
distance away.
Small differences must often be observed in an a-c voltage that is not
properly read on one of the linear scales under the knife-edged portion of the
ointer. If the voltage is above about 0. 5 volt, the difference can be observed
on the corresponding linear scale with only a small error. For voltages less
than about 0. 5 volt, the difference read on the linear soale must be corrected
for the non-linearity of the a-c scale. Of course, the actual voltage level, if it
must be known, should be read on the correct a-c scale.
SECTION 2.0
CIRCUIT AND CONSTRUCTION
2.1 GENERAL CONSTRUCTION
In order to have an instrument that can be easily handled and that occupies a minimum of bench space, the Type 1800-A Vacuum-Tube Voltmeter has been made as compact as possible. The tubes, with the exception of
V-1, and most of the circuit components are mounted on a chassis that is attached to the panel on four insulating supports. The cable connection between
the chassis and the panel is arranged so that the chassis can be detached and
swung to one side. This makes all circuit components easily acces·sible for
servicing.
2.2 PROBE
The small shielded probe contains the diode rectifier. It is of cylindrical
construction with a rotating metal cover provided to close the opening through
which the acorn-tube diode is inserted. When this opening is closed, the probe
5
GENERAL RADIO COMPANY·
is completely shielded except for a small area of insulation at the front.
A metal cap that is used to attach the various fittings described below
screws onto the end of the probe. The body of the probe behind the end cap is
insulated by a phenolic cover that slips in place and is secured by an insulated
nut.
When it is not desired to connect the a-c voltage directly to the probe, the
probe can be insened into the back of the a-c terminals on the panel and the
a-c voltage can be applied to those terminals.
A three-wire shielded cable between the probe and the chassis connects the
rectifier circuit to the d-e amplifier circuit.
2.3 PROBE FITTINGS
The probe fittings are stored in the compartment at the top of the cabinet.
They consist of three Type 274 Plugs, both male and female Type 774 Coaxial
Terminals, and a 50-ohm, concentric, terminating resistor. These fittings are
attached by the metal cap that scre~s onto the end of the probe.
2.4 D-C AMPLIFIER
The d-e amplifier consists of two balanced triodes operating in a highly
(jegenerated circuit. The rectified alternating voltage is applied directly to the
control grid of one triode, and a diode that serves only to balance the effect of
the initial voltage of the rectifying diode is connected to the control grid of the
second triode. Both triodes are contained in one envelope.
Figure 4· Vitw of tht storage
compartment at the top of the
cabinet. The various probe fillings
are stored here and the prohe itself is placed here when not in
use or when the panel A.C
terminals are used.
6
TYPE 1800-A VACUUM- TUBE VOLTMETER
2.5 INDICATING METER
The indicating meter is connected in series with precision resistors between
the cathodes of the two triodes. The voltage range of the instrument is
changed by changing the value of the series resistance.
2.6 ZERO CONTROLS
There are three zero controls. The fine ZERO control, which is used during
normal operation of the instrument, is located on the right-hand side of the
panel.
The COARSE ZERO adjustment, which is used to adjust the position of the
ZERO control, is located on the bottom of the instrument chassis. A bottom
view of the chassis is shown in Figure 8.
The A-C ZERO adjustment, which is used to adjust the a-c zero setting of
the panel ZERO control to coincide with the d-e zero setting, is located next
to the COARSE ZERO adjustment on the bottom of the chassis.
2.7 DEGENERATION
On the higher voltage ranges the d-e amplifier is highly degenerated. On the
lower voltage ranges the degeneration is less because of the decreased value
of the resistance in series with the indicating meter. High degeneration without excessive plate voltage requirements is obtained by connecting a degenerated triode in series with the cathode of each amplifier triode. The two
degenerated triodes are also contained in one envelope.
2.8 POWER-SUPPLY STABILIZATION
In order to allow satisfactory operation of the instrument at various line
voltages, the d-e plate supply and the a-c heater voltages of the two diodes
are stabilized. The d-e supply voltage is stabilized wiLh an electronic regulator
circuit consisting of two miniature vacuum tubes and two small neon tubes.
I he diode heater voltages are stabilized by use of a ballast tube.
2.9 RECONNECTING POWER TRANSFORMER FOR DIFFERENT LINE VOLTAGE
The transformer primaries can be connected for either 11 5-volt or 230-volt
operation. The a-c line is conne~ted, through the power switch and fuses. to
power transformer terminals :\o. 17 and No. 20. For 115-volt operation connect terminal \Jo. 17 to terminal No. 19 and terminal :'\lo. 18 to terminal No.
20. For 230-volt operation connect terminal ~o. 18 to terminal ~o 19. If the
transformer connections are changed from the factory connections, reverse
the plate under the power input socket, and replace the two line fuses. (See
Parts List.)
7
GENERAL RADIO COMPANY
SECTION 3.0
OPERATING CHARACTERISTICS
3.01 Voltage Range: 0.1 to 150 volts, a-c, in six ranges (0. 5, I. 5, 5, 15, 50 and
150 volts, full scale); 0.01 to 150 volts, d-e, in six ranges (0. 5, I. 5, 5, 15, 50 and
150 volts, full scale).
3.02 Accuracy: 0-C, ± 2% of full scale on all six ranges. A-C, ± 2% of full
scale on all six ranges for sinusoidal voltages.
3.03 Waveform Error: On the a-c voltage ranges, the instrument operates as
a peak voltmeter calibrated to read r-m-s values of a sine wave, or 0.707 of the
peak value of a complex wave. On distorted waveforms the percentage deviation of the reading from the r-m-s value may be as large as the percentage of
harmonics present.
3.04 Frequency Errors: At high frequencies resonance in the input circuit
and transit-time effects in the diode rectifier introduce errors in the meter
reading. The resonance effect causes the meter to read high and is independent
of the applied voltage. The transit-time error is a function of the applied voltage and tends to cause the meter to read low. The curves of Figure 5 give the
frequency correction for several different voltage levels. It will be noted that
at low voltages the transit-time and resonance effects tend to cancel, while at
higher voltages the error is almost entirely due to resonance. The resonant
frequency with cap on but plug removed is about I 050 Me.
At low frequencies the response drops off because of the increasing reactance
of the series capacitance in the input circuit. At 20 cycles per second the drop
is 2% or less.
1.2
.I
-i--::
1.0
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b::::::;
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u
t 0
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... ...
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~ ~
g g
I
!.--
,\
0.5V.
~ ~I
~
1.5V.
5V.
115V.
50V.
I
~ov.
0.7
I
I
0.6
I
1
10
100
I
1000
FREQUENCY- Me
Figure f. Frequency corrections for a number of different indicated voltages, taken with
cap on hut plug removed. The curve marked oo is included to show the complete resonance
effect.
8
TYPE 1800-A VACUUM-TUBE VOLTMETER
3.05 Input Impedance: The equivalent a-c input circuit is a resistance in
parallel with a capacitance. At low frequencies, the equivalent parallel resistance is 25 megohms. At higher frequencies this resistance is reduced by
losses in the shunt capacitance. The eqwvalent parallel capacitance at radio
frequencies is 3.1 J.J.J.J.f with the probe cap and plug removed. At audio frequencies this capacitance increases slightly. The probe cap and plug add approximately 1.2J..I.J.J.f. Figure 6 gives the variation of Rp and Xp with frequency.
On the d-e ranges the input resistance is either 10 megohms or open grid,
depending on the terminals used.
3.06 Power Supply: 105 to 125 volts or 210 to 250 volts, a-c, 50 to 60 cycles.
The instrument incorporates a voltage regulator to compensate for supply
variations over th"is voltage range. The power input is less than 25 watts.
3.07 Tubes: Two Type 9005, two Type 6SL7-GT, one Type 6AT6, one Type
6C4, one Type 6X5-GT, one Type 3-4, and two Type 991 are used; all are
supplied.
3.08 Accessories Supplied: A seven-foot line connector cord, spare fuses,
Type 274 and Type 774 terminations and 50-ohm terminating resistor for
probe.
3.09 Mounting: Black crackle finish aluminum panel mounted in a shielded
walnut cabinet.
3.10 Dimensions: ('Width) 7%" x (depth) 7,Y2" x (height) 11 Ys", over-all.
3.11 Net Weight: 13 po •.mds.
~
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:
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TYPE 1800-A IIIGUUM-TUliE VOLTMETEII
"""'
'
100
AIIRALLEL COMPONENTS
'--..~ ~~
-~
~~
--
OF
IN PUT IMPEDANCE
I
~-+----l-1-~-+--+--""'--*---+--,"'.
"~ I
I
~
)1-1
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----1---L----L-~_l----l.
0.01 iLl
0.001
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• WfTH PROK CAP OFf
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j_ j_
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1000
FREQUENCY- Me.
Figure 6. Plot of impedance versus frequ.tncy for the parallel components of input impedance. The equit•alent ptlr(Jl!el capacitance is J. z 1-11-'f.
9
GENERAL RADIO COMPANY
SERVICE AND MAINTENANCE NOTES
FOR THE
TYPE 1800-A VACUUM-TUBE VOLTMETER
1.0 FOREWORD
1.1 This Service Information together with the information given in the
Operating Instructions should enable the user to locate and correct difficulties
resulting from normal usage.
1.2 l\1ost of the components mentioned in these notes can be located by
referring to the photographs.
1.3 i\1ajor service problems should be referred to the Service Department
which will cooperate as far as possible by furnishing information and instructions, as well as hy shipping any replacement parts which may be required. If
the instrument is more than one year old. a reasonable charge may be expected
for replacement parts or for complete reconditioning and recalibration if the
voltmeter is returned.
1.4 Detailed facts giving type and serial numbers of the instrument and
parts, as well as operating conditions, should always be included in your report
to the Service Department.
2.0 GENERAL
If the voltmeter becomes inoperative, a few simple checks should be made
before removing the instrument from its cabinet.
2.1 Check the power line source for proper voltage and frequency.
2.2 Test the pov..·er-supply cord for an open circuit or for poor contact in
the power socket.
2.3 Check the fuses mounted on the panel for open circuits, and be sure
they are tight in their clips.
3.0 VOLTMETER DOES NOT OPERATE PROPERLY
3.1 See that all tube 1laments are lighted.
3.2 ~1eter lamps do not light, refer to Section 4.0
3.3 :vleter does not move up scale and return to zero when the voltmeter
·s turned on with VOLTAGE RANGE switch set to 0.5, refer to Section 5.0.
3.4 Unable to set to "0" with ZERO control, voltmeter set to D-C, refer
to Section 6.0.
3.5 Unable to set to "'0" with ZERO control, voltmeter set to A-C, refer
to Section 7.0.
3.6 \.1etcr does not read with D-C signal applied to the I 0 .i\1EG n input
erminals, refer to Section R.O.
3.7 Meter does not read with D-C signal applied to the OPEN GRID
input terminals, refer to Section 9.0.
10
TYPE 1800-A VACUUM-TUBE VOLTMETER
3.8 I\1eter does not read with an A-C signal applied to input terminals,
refer to Section I 0.0.
3.9 l\11eter reads incorrectly on one or more voltage ranges, refer to Section
11.0.
3.10 Recalihratic/il, refer to Section 12.0.
3.11 Power suprly inoperative or has low output voltage, refer to Section
!3.0.
3.12 Replacement of components, refer to Section l..J..O.
3.13 Vacuum-tube data, refer to Section 15.0.
4.0 METER LAMPS DO NOT LIGHT
4.1
4.2
4.3
4.4
Test fuses F-1 and F-2 for open circuits.
Check lamps P-1 located in meter case.
Check contacts and operation of power switch S-2.
Check connections to and continuity of transformer T-I.
5.0 METER DOES NOT MOVE UPSCALE AND RETURN TO ZERO WHEN
THE VOLTMETER IS TURNED ON WITH VOLTAGE RANGE SWITCH
SET TO 0.5.
5.1 Check tube V-3 and operating voltages.
5.2 Check operation of switch S-1.
5.3 Check resistors R-1 0 and R-1 I for open and short circuits.
5.4 Check condensers C-2 and C-3 for open and short circuits.
5.5 Defective meter M-I.·
5.51 ?\:ominal sensitivity is I 00 microamperes d.c. for full scale deflection. Sec Section 1 I. 11.
5.52 If the meter is defective, a replacement shouiJ be ordered from the
Service Department. The General Radio Company cannot assume responsibility for any local repairs to the meter, although such repairs may be necessary
in an emergency.
5.6 Check tube V-..J. and operating voltages.
.
5.7 Check resistors R-29, R-30, R-36, R-37, R-38 and R-39 for open and
short circuits.
5.8 Check resistors R-12, R-13, R-21 and R-22 for continuity.
5.9 Check switch S-3 for continuity and proper operation.
6.0 UNABLE TO SET METER TO "0" WITH ZERO CONTROL, VOLTMETER
SET TO D-C
--
6.1 Check the d-e voltage between B+ and 8- to be ..J.50 volts ±5.0
volts. Refer to Section I3.5.
6.2 Check resistors R-33, R-3..J. and R-35 for open anJ short circuits.
Refer to Sections 5.7 and 5.8.
Il
GENERAL RADIO COMPANY
6.3 Check that tube V-3 has low grid current. This can be done by the
following procedure.
6.31 Set the switches for the 0. 5-volt d-e range.
6.32 Place the connecting link across the D-C OPEN GRID terminals ..
6.33 Adjust the meter to zero with the ZERO control or the COARSE
ZERO adjustment.
6.34 Short circuit the D-C I 0 :'vfEG Q terminals. The meter reading
should not be more than .0 I 5 volt.
6.35 Remove ballast tube V-2 from its socket.
6.36 With the short circuits still across both sets of D-C terminals, adjust the meter to read 0.2 volt using either the ZERO control or the COARSE
ZERO adjustment.
6.37 Turn switch S-1 to A-C. The meter should not vary by more than
ten scale divisions above or below the 0.2-volt reading. The reading should
stabilize within a few seconds and the meter should show no drift.
6.38 If the tube fails to pass any of the above tes.ts it should be rejected
in favor of another tube.
7.0 UNABLE TO SET TO "0" WITH ZERO CONTROL, VOLTMETER SET TO A-C.
7.1 Refer to Sections 6.1 and 13.5.
7.2 Check tube V-1 and operating voltages, refer to Section 14.1.
7.3 Check that the cathode of V-1 is grounded to the shell of the probe.
7.4 Check resistors R-1 and R-2 for open and short circuits.
7.5 Check tube V-2 for continuity and operating voltages.
7.6 Check resistors R-5 through R-9.
7. 7 Check tube V- 5 and operating voltages.
7.8 Check resistors R-31 and R-32 for open and short circuits.
7.9 Check operation of switch S-1.
7.10 If it is necessary to replace either or both V-1 and V-5, follow the
procedure of Section 1.4 of the Operating Instructions, trying various tubes
until tubes are found which will permit a satisfactory zero adjustment.
8.0 METER DOES NOT READ WITH D-C SIGNAL APPLIED TO THE JO MEG 0
INPUT TERMINALS
8.1
nals.
8.2
8.3
8.4
8.5
Be sure that the connecting link is shorting the OPEN GRID termiCheck resistor R-4 for a short circuit.
Check resistor R-51 for an open circuit.
Check condenser C-7 for a short circuit.
Refer to Section .'i.O.
9.0 METER DOES NOT READ WITH D-C SIGNAL APPLIED TO THE OPEN
GRID INPUT TERMINALS
--
9.1
9.2
Be sure that the connecting link is shorting the I 0 MEG Q terminals.
Refer to Sections 5.0, 8.3, and 8.4.
12
TYPE 1800-A VACUUM-TUBE VOLTMETER
10.0 METER DOES NOT READ WITH A-C SIGNAL APPLIED TO INPUT
TERMINALS
10.1
10.2
Check condenser C-I for an open or a short circuit.
Refer to Sections S.O and 7.0
11.0 METER READS INCORRECTLY ON ONE OR MORE VOLTAGE RANGES
11.1 Check meter sensitivity.
11.11 Full scale sensitivity of the meter, shunted by R-52. is I 02 microamperes de. R-52 is picked in the standardizing laboratory to provide this
value of sensitivity. Refer to Section S.S.
11.2 D-C measurements:
11.21 Check resistors R-21 through R-28.
11.22 Try changing tube V-3. Refer to Section 6.3.
11.3 A-C measurements:
11.31 Check resistors R-I2 through R-20.
11.32 Try changing tubes V-1, V-3 and V-5. Refer to Sections 6.3 and
7.10.
11.4 Check calibration of 0.5 and 1.5 volt VOLTAGE RANGE. Refer
to Section 12.0.
12.0 RECALIBRA TION
12.1 Accurately known sources of a-c and d-e voltages should be available
before attempting any recalibration of this instrument.
12.2 Check zero adjustments, refer to Section 7.10 of these Notes and
Section I.4 of the Operating Instructions.
12.3 Refer to Section 6.1 and I3.5.
12.4 D-C Calibration
12.41 Set VOLTAGE RANGE switch to the 0. 5- and 1. 5-volt positions
and apply the corresponding d-e voltage to the D-C IO MEG n input terminals with the connecting link shorting the OPEN GRID terminals.
12.42 Set the meter to full scale by means of potentiometer R-22 for the
0. 5-volt range and potentiometer R-23 for the 1. 5-volt range. These are
marked D. C. CAL, 0. 5 v and 1. 5 v, respectively, on the bottom subpanel.
12.5 A-C Calibration:
12.51 Set VOLTAGE RA:-\'GE switch to the 0. 5- and 1. 5-volt positions
and apply the corresponding sine-wave, root-mean-square, a-c voltages to the
A-C input terminals.
12.52 Set the meter to full scale by means of potentiometer R-13 for the
0. 5-volt range and potentiometer R-14 for the ·I. 5-volt range. These are
marked A. C. CAL, 0. 5 v and I. 5 v, respectively, on the bottom subpanel.
13
GENERAL RADIO COMPANY
13.0 POWER SUPPLY INOPERATIVE OR HAS LOW OUTPUT VOLTAGE
13.1 Check tubes V-6, V-7, V-8, V-9 and V-1 0 and operating voltages.
13.12 ~ote that one plate each of V-9 and V-1 0 glows evenly.
13.2 Check connections to and continuity of transformer T-1.
13.3 Check resistors R-40 through R-50 for open and short circuits.
13.4 Check condensers C-5 and C-6.
13.41 NOTE. The d-e voltage across either one of these condensers
should not exceed 42 5 volts maximum. If the voltage across either condenser
exceeds 425 volts the other condenser should be replaced, assuming that R-49
and R-50 are not defective.
13.5 The output voltage of the power supply, as measured between B+
(slate-red wire) and B- (yellow-green wire) on the terminal strip on the
right side of the instrument above the power receptacle, should be set to 450
volts± 5.0 volts, de, as measured with a 20,000 ohm-per-volt voltmeter.
13.51 Set the input line voltage to 100 volts, ac.
13.52 Adjust potentiometer R-45 until B+ voltage reads 450 volts.
13.53 Increase the line voltage to 130 volts.
13.54 Adjust potentiometer R-43 until B+ again reads 450 volts.
13.55 Repeat the ahove procedure until the B+ voltage remains constant for any input voltage between 105 and 125 volts.
14.0 REPLACEMENT OF COMPONENTS
Due to the compact design and construction of this instrument and the
number of component parts mounted in the availahle space, a number of
mechanical expedients have been used. The following instructions should be
followed when replacement of component parts is necessary .
.14.1 Probe
14.11 Unscrew spring ring at rear of probe.
14.12 Pull back black phenolic housing.
14.13 Rotate the rotatable metal shield exposing tube V-1.
14.14 Remove tube V-1.
14.15 Unscrew the banana plug probe and the retaining hex nut at the
front of the probe.
14.16 Unscrew and remove the three black-headed screws in the retaining plate.
14.17 Remove the retaining plate.
14.18 Remove the snap ring holding the inner assembly in place using a
pair of thin, long-nosed pliers to squeeze the ends of the ring together.
14.19 Unscrew the metal cap at the front of the probe and pull back the
rotatable metal shield.
14.110 Unsolder the joint holding the inner suspension to the metal
shell.
14
TYPE 1800-A VACUUM-TUBE VOLTMETER
14.111 Remove the entire inner assembly by pulling on the cable being
'
careful not to damage R-1 and R-2 which are now supporting C-1.
14.112 CAUTION: When using a soldering iron to replace components,
be careful not to overheat the insulating blocks of polystyrene at the front and
rear of the inner assembly as these melt at a relatively low temperature.
14.2 Main instrument.
14.21 Remove the four screws that hold the subpanel on which the
tubes are mounted to the four bakelite mounting posts.
14.22 Unsolder the two black covered wires that run from the socket of
V-3 to switch S-1. These points are marked "X" in the photographs.
14.23 The subpanel can now be laid back toward the input terminal
end of the front panel to expose most of the component circuit elements.
15.0 VACUUM- TUBE DATA
The table below lists tube socket voltages measured from socket pin to
ground, unless otherwise indicated, using a 20,000 ohm-per-volt meter
(Weston 772 Analyzer). D-C voltages may vary ±20%.
SYM.
TYPE
2
1 and 5
3.2-3.9v AC
J
5
4
7
6
8
Diode Rect!.:'ier
V-1
9005
V-2
V-.3
Amperite
J-4
6SL7GT
V-4
6SL7GT
-212
1 • .35
-215
V-5
9005
-.25
V-6
6C4
1 and 4
-.05
3.2-.3.9v AC
300
V-7
6AT6
.25
.3 and 4
6 • .3v AC
V-8
6X5GT/G
V-9
V-10
991
991
CONDITIONS:
FUNCTION
SOCKET PIN NUMBER
1
-.75v
2 and 7
5.8v AC
162
1.35
47
Ballast Tube
162
-212 1..35
1..35 7 and 8
6.;.v AC
-215 7 and 8
6 • .3v AC
D-C Amplifier
Degeneration
Tube
Balancing Diode
.3 and 4
6.Jv AC
1.32
162
Regulator
132
Regulator
2 and 7 470v AC
470v AC
6 • .3v AC
62v DC across terminals
65v DC a~~oss terminals
Input--ll5v - 60 cycles.
SWitch S-1 set to DC, D-C input terminals short-circuited.
VOLTAGE RANGE switch set to 0.5.
B+ set for 450 volts, de.
15
Rectifier
Neon Regulator
Neon Regulator
ORDER REPLACEMENT PARTS FROM GENERAL RADIO COMPANY
PARTS LIST
s
bol
Rat in
and Tolerance
Mfr.'s
T e No.
Mfr.
RESISTORS
R-1
R-2
R-4
R-5
R-6
R-7
R-8
R-9
R-10
R-11
R-12
R-13
R-14
R-15
R-16
R-17
R-18
R-19
R-20
R-21
R-22
R-23
R-24
R-25
R-26
R-27
it-28
R-29
R-30
R-31
R-32
R-33
R-34
R-35
R-36
R-37
R-38
R-39
R-40
R-41
R-42
R-43
R-44
R-45
R-46
R-47
R-48
R-49
R-50
R-51
*R-52
~b
100 JIC
100 JIC
10 )LQ
4700 Q
4700 Q
20 g
6 Q
20 Q
18 )LQ
18 )LQ
1300 Q
1 kQ
3 kQ
11.5 kQ
46.1 kQ
133-4 kQ
474.4 kQ
350 kQ
l'ILQ
1300 Q
1 kQ
3kQ
8500 Q
33.8 kQ
96.4 kQ
338.9 kQ
964 kQ
0.1 JIC
O.l 1LQ
100 )1;2
100 )LQ
47 kQ
20 kQ
47 kQ
0.75 M.Q
10 kQ
lM.Q
0.2 M.Q
5.6
3.9
M.Q
MQ
2.2 kQ
0.2 )LQ
0.39 )1;2
0.2 )LQ
0.22 )LQ
lKQ
lKQ
4·7 MQ
4.7 )1;2
10 )1;2
+40%,-20%
+40%,-20%
.±.10%
.:!:.10%
.:!:.10%
.:!:.5%
.:!:.10%
.:!:.5%
.±.10%
.:!:.10%
.±.1%
.:!:.10%
+10%
±1%
.:!:.0.25%
.:!:.0.25%
,:!.0.25%
,:!.0.25%
.:!:.0.25%
.:t.l%
,:tlO%
.:!:.10%
.:!:.1%
.:!:.0.25%
.:!:.0.25%
,:t0.25%
.:!:_0.25%
.±10%
.:!:.10%
,:!.20%
.:!:.20%
.:!:.10%
.±10%
.:!:.10%
.:!:.1%
+10%
±1%
.±1%
.±.10%
+10%
1:5%
,:!:10%
.±10%
.:!:.10%
.:!:.10%
.±1%
.:t.l%
.:!:.10%
.:!:.10%
.:!:.10%
.:!:.10%
IRC
IRC
IRC
IRC
IRC
IRC
GR
IRC
IRC
IRC
IRC
GR
GR
IRC
IRC
IRC
IRC
IRC
IRC
IRC
GR
GR
IRC
IRC
IRC
IRC
IRC
IRC
IRC
ERIE
ERIE
IRC
GR
IRC
CCC
GR
CCC
CCC
IRC
IRC
IRC
GR
IRC
GR
IRC
CCC
CCC
IRC
IRC
IRC
IRC
BTX-1/2 ~Special~
BTX-1/2 Special
BT-1/2
BT-1/2
BT-1/2
BW-2
POSC-862
BW-2
BT-1/2
BT-1/2
WW-3
POSW-862
POSW-862
WW-3
WW-3
WW-3
WW-4
WW-4
WW-5
WW-3
POSW-862
POSW-862
WW-3
WW-3
WW-3
WW-4
WW-5
BT-1/2
BT-1/2
504
504
BT-1/2
410-,12
BT-l 2
X-1/2
POSW-862
X-1/2
X-1/2
BT-1/2
BT-1/2
BT-1/2
POSC-860
BT-1/2
POSC-860
BT-1/2
X-1/2
X-1/2
BT-1/2
BT-1/2
BT-1/2
BT-1/2
to determine value when adJusting meter.
PARTS LIST (cont)
Symbol
Rating and Tolerance
Mfr.
Mfr.'s
Type No.
CONDENSERS
C-1
C-2
C-3
C-4
C-5
C-6
C-7
C-8
0.006
0.01
0.01
0.5
4
4
0.01
0.01
~
GR
GR
GR
GR
GR
GR
AEROVOX
AEROVOX
~f
~r.
j..lf
J.Lf
J.Lf
J.Lf
J.Lf
.:!:10%
_±10%
- 1800-27
COP-7,2
COP-7,2
COL-13
COE-19
COE-19
1467
1467
TUBES
V-1
V-2
RCA
Amperite
RCA
RCA
RCA
RCA
RCA
RCA
RCA
RCA
V-3
V-4
V-5
V-6
V-7
V-8
V-9
V-10
9005
3-4
6SU7-GTY
6SL7-GT
9005
6C4
6AT6
6X5-GT/G
991
991
FUSES
For 115 Y. operation
F-1 = 0.3 amp.
Slow Blow 3AG
F-2 = 0.3 amp.
Slow Blow 3AG
GR
GR
FUF-1
FUF-1
For 230 v. operation
F-1 = 0.15 amp.
Slow Blow 3AG
F-2 = 0.15 amp.
Slow Blow 3AG
GR
GR
FUF-1
FUF-1
METER
M-1
100
P-1
6.3·v. 2 Req. (in M-1)
~
amp.
PILOT LAMP
GR
MEDS-26
2LAP-939F
SWITCHES
S-1
S-2
S-3
~WRW-30
DPST
Part of S-1
SWRW-31
PLUG
PL-1
CDPP-562A
TRANSFORMER
T-1
345-444-2
c_a_rwl and Cobrn!'l $hreld
---~-----------------------------
BVOLTAGE
RANGE
0:~·5-Jl.!:~
:y'"'
WIRING Ot4G8AM
u5or230V
INPU7
",_"""
!§IJO-r4
w
VACUUM-TUBE VOLTMETER
I
I
I
I
I
I
~~·-~-
I
L--------------------------------------------~
Fi!l~re 7-
Complete wiring dia ram of th, Type 18oo-A Vacuum-Tube Voltmeter.
F1ym 9· lnt"Uw vitJtJ •/1" IW.fPfftl b111 km L.UJ b~ (~tr S«tit. ~.;.:1
aJ M..1Nirrw1Kt N#lu).
•J !tn•iu
MULTIPLIERS
Two 10:1 multipliers are available for _use with the Type 180Q..A
Vacuum~Tube
and the Type
to 30 kc.
Voltmeter: the Type
1800~P3,
1800~P2,
for use above JOke,
for use at de and at frequencies up
Complete specifications for these multipliers will be
furnished on request.
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