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Page Title:
Table 2-6. Troubleshooting of Laser Power Supply Control C-9135/VVG-1 (A77) - Continued |
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 TM 9-1240-369-34
Table 2-6. Troubleshooting of Laser Power Supply Control C-9135/VVG-1 (A77) - Continued
Item
No.
Malfunction
Probable cause
Corrective action
RANGE lamp does not flash
meter on R/T tester indicates near
(unit A75)-continued
center of red band. If this indication is
obtained, continue with step 18. If the
RCVR-XMTR status meter indicates
outside the red band, continue with
step 6.
6.
Disable interlock switch S1 on chassis.
7.
Remove A77A9 module (para 3-5d).
8.
Using a ground rod, ground coil (high-
voltage terminal of PFN A77Z1 for 5
seconds.
9.
Using multimeter, measure resistance
from PFN A77Z1 coil terminal to
ground. If resistance is greater than 1
megohm. Continue with step 12. If
resistance is less than 1 megohm,
continue with step 10.
10
Replace PFN A77Z1 (para 3-5 g).
11.
Perform steps 14 thru 18.
12.
Replace A77A9 module (para 3-5 d).
13.
Adjust PFN voltage control A77, A9R10
six turns counter-clockwise.
14.
Enable interlock switch S1 on chassis.
15.
Using R/T tester, adjust A77, A9R10 for
proper transmitter output energy
16.
Disable interlock switch S1 on chassis.
17.
Remove unit from hot mockup.
18.
Replace gasket and unit cover
assembly (para 3-5a).
19
Purge unit (TM 9-2350-230-12).
2
RANGE(METERS) indicator
Counters circuit card assembly,
1.
Install failed unit in hot mock-up.
(unit A79) does not display
A77A5: reply gating circuit card
2.
Enable interlock switch S1 on
correct readout.
Assembly A77A4, low voltage
chassis.
Interface power supply A77A2.
3.
Perform portion of Checkout
Interface circuit card assembly
A77A7 or A77 unit.
duplicate malfunction.
4.
Disable interlock switch S1 on chassis.
5.
Remove A77A4 card (para 3-5c).
6.
Install extender card (4, table 2-1).
7.
Insert A77A4 card into extender
card connector.
8.
Enable interlock switch S1 on chassis.
9.
Perform step 3 and continue with step
10.
10.
Enable switch S1 on A77A4 card.
11
Using oscilloscope, measure signals at
pins 24, 25, and 26 of A-7A4 card. If
signals compare
2-14
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