TM 11-6625-444-14-2
NOTE
(8) If the drift is less than 50 counts from
the "cold" reading, proceed to step b for volt-
meter with serial prefix 00001A thru 00010A,
If the differential voltmeter indica-
tion tends to oscillate, adjust A7-
00096A and higher or step c for voltmeter with
R113 slowly counterclockwise un-
serial prefix 0 0 0 1 1 A thru 00039A, 00052A,
til the oscillation stops. Re-adjust
00055A and 00057A thru 00095A. If the drift is
greater, continue with step a. (9).
A7-R144 for a minimum reading on
the differential voltmeter.
(9) Adjust control A7-R30 for a reading on
the dc differential voltmeter that is three times
(8) Press the SLOW RESPONSE pushbutton
greater than the observed "hot" reading - in the
to the "in" position. Adjust R148 for a minimum
same direction.
Allow a few minutes for the reading to settle af-
ter initial adjustment. If necessary, repeat the
(10) Repeat step (6) through (8) as many
Release the SLOW RESPONSE
adjustment.
times as required, until the drift is within the
specified amount.
pushbutton back to the "out" position.
(9) Switch A7-S17 to the TEST position.
(10) Set the volts/div switch on the oscil-
b. Overall Zero Adjustments (A7-R83, R94,
l o s c o p e to the 5 mV position and select dc
R113, R144, R148). Applies to units with serial
coupling. Set the time/div switch to 10 ms/div
number 00001A thru 00010A, 00096A and high-
and set the probe switch to the REF position.
er.
Adjust the CH1 vertical position control to center
the trace vertically.
(1) Connect the equipment as shown in
the X10 position and monitor the signal at TP3
as indicated in figure 6-28.
(2) Select the 200 V range and AC VOLTS
function on the voltmeter.
(12) Adjust A7-R94 for a zero dc indica-
tion (centered vertically) on the oscilloscope.
(3) Select the 1 V range and 100 uV NULL
sensitivity on the differential voltmeter (A3) and
set its dials to +0.0000.
NOTE
The waveform may contain some com-
(A3) LO terminal to A7-TP2 on the voltmeter
ponent of noise. Adjust A7-R94 so
and connect the HI terminal to A7-TP1 on the
that the waveform displayed is sym-
voltmeter (see figure 628).
metrical vertically about the center
horizontal graticule line.
(5) Adjust the front panel AC NULL con-
trol on the voltmeter for a reading of zero ( 10
uV) on the dc differential voltmeter.
TP4 and change the volts/div switch to 20 mV/-
div position. (Vertical sensitivity will now be 200
(6) Disconnect the dc differential voltme-
mV/div.
ter HI test lead from A7-TP1 and connect it to
A7-TP5 on the voltmeter.
(14) Change the probe switch to the REF
position and, if necessary, readjust the CH1 ver-
(7) Adjust A7-R144 for a reading of zero
(10 uV) on the dc differential voltmeter.
tical position control to center the trace vertical-
6-52
