TM 11-6625-444-14-2
Iy on the oscilloscope. Change the probe switch
(1) Connect the equipment as shown in
back to the X10 position.
(2) Select the 200 V range and AC VOLTS
(15) Adjust A7-R83 so that the dc level of
function on the voltmeter.
the signal displayed on the oscilloscope is -700
mV.
(3) Select the 1 V range and 100 uV NULL
sensitivity on the differential voltmeter (A3) and
(16) There may be some interaction be-
set its dials to +0.0000.
tween the two adjustments. Repeat steps (10)
through (15) until both requirements are satis-
fied.
(4) Connect the dc differential voltmeter
(A3) LO terminal to A7-TP2 on the voltmeter
and connect the HI terminal to A7-TP1 on the
(17) Set the differential voltmeter dials to
voltmeter (see figure 6-28).
-.0003 and set its drum dial to 50 (i.e. -350 uV).
(5) Adjust the front panel AC NULL con-
(18) Adjust A7-R144 for zero null meter
trol on the voltmeter for reading of zero (10
indication (50 uV) on the differential voltmeter.
uV) on the dc differential voltmeter.
(19) Disconnect the differential voltmeter
f r o m A7-TP5 and connect the oscilloscope
(6) Disconnect the dc differential voltme-
ter HI test lead from A7-TP1 and connect it to
probe in its place. Set switch A7-S17 to the
A7-TP5 on the voltmeter.
NORM position.
(7) Adjust A7-R 144 for a reading of zero
(20) Change the oscilloscope volts/div
(10 uV) on the dc differential voltmeter.
switch back to 5 mV/div.
(21) Adjust A7-R 113 slowly clockwise un-
NOTE
til a low frequency oscillation just appears on the
oscilloscope display. Rotate A7-R1 13 counter-
If the differential voltmeter indication
clockwise to the point where the oscillation just
tends to oscillate, adjust A7-R113
disappears.
slowly counterclockwise until the os-
cillation stops. Readjust A7-R144 for
a minimum reading on the differential
(22) Set switch A7-S17 back to the TEST
position and reconnect the differential voltmeter
test lead to A7-TP5. Disconnect the oscillo-
scope probe from the test point.
(8) Press the SLOW RESPONSE pushbut-
Adjust R148 for a
t o n to the "in" position.
(23) Set the differential voltmeter dials to
minimum reading on the differential voltmeter (
+.0002 (i.e. +200 uV). Adjust A7-R 144 for zero
10 uv). Allow a few minutes for the reading to
null meter indication ( 50 uV) on the differential
settle after initial adjustment.
If necessary,
repeat the adjustment. Release the SLOW RE-
SPONSE pushbutton back to the "out" position.
(24) Switch A7-S17 back to the NORM po-
sition.
The differential voltmeter null reading
(9) Switch A7-S17 to the TEST position.
should remain unchanged (50 uV).
(10) Set the volts/div switch on the oscil-
loscope to the 20 mV position and select dc
coupling. Set the time/div switch to 10 ms/div
c. Overall Zero Adjustments (A7-R94, R113,
and set the probe switch to the REF position.
R144, R148). Applies to units with serial number
Adjust the CH1 vertical position control to center
0 0 0 1 1 A thru 00039A, 00052A, 00055A and
the trace vertically.
00057A thru 00095A.
6-53
