Table 2-6. Troubleshooting of Laser Power Supply Control C-9135/VVG-1 (A77)

TM 9-1240-369-34

Table 2-5. Troubleshooting of R/T Control C-8728/VVG-1 (A 75) - Continued

Item

No .

Malfunction

Probable cause

Corrective action

Reticle lamp illumination in

Using multimeter, check continuity

receiver- transmitter unit is

between terminal1 of R1 and ground. If

not varied by RTCL ILLUM

continuity exists, continue with step 8.

control-

If continuity does not exist return unit to

depot for repair.

8. Replace RTCL ILLUM potentiometer

(para 3-3e)

9. Perform step 2 and continue with step

10.

10. Remove unit from hot mock-up.

11. Replace cover seal and unit cover

assembly (para 3-3a).

12. Install unit shipping cover (para 3-3f)

and purge unit (TM 9-2350-230-12).

contained in table 2-6. This table is to be used after

2-8.

Troubleshooting of Laser Power Supply

organizational maintenance has determined the

Control C9135/VVG-1 (A77)

malfunction exists in the power supply control unit. A

a. Test Setup. Set up hot mock-up as described in

circuit card puller (6, table 2-1) is provided in the special

paragraph 2-4.

tools and test equipment to facilitate removal of the A77

b. Troubleshooting Procedures. All troubleshooting

circuit card assemblies.

procedures for the power supply control unit are

Table 2-6. Troubleshooting of Laser Power Supply Control C-9135/VVG-1 (A77)

Item

No.

Malfunction

Probable cause

Corrective action

WARNING

Ensure that power is off when installing or removing units in hot mock-up, or installing or removing

components or assemblies in units.

NOTE

It is assumed that the access cover assembly of the power supply control unit is removed throughout this

table. Enable switch S1 under access cover by pulling lever outward and switch S2 on chassis, located

adjacent to PFN A777Z1, by pressing down on its lever. Disable the switches by releasing the levers. For

location of PFN, refer to figure 3-2. Extender card test points are connected to corresponding circuit card

pin numbers.

PFN charge power supply

Or RANGE lamp does not flash

1. Install failed unit in hot mock-up.

A77A9, or PFN A77Z1.

(unit A75).

2. Enable interlock switch S1 on

chassis.

3. Perform portion of (para 4-2a)

which will duplicate malfunc tion.

4. Using multimeter, measure

voltage at pin 2-7 of interface

circuit card assembly A77A7. If

multimeter indicates + 15.0 1.0

V. continue with step 5. If

multimeter does not indicate

+15.0 1.0 V. perform steps 20

thru 26 in "Corrective action"

column for item No. 2.

5. Press PRESS TO TEST switch

on PFN charge ammeter. Observe

that meter does not indicate more

than 82 microamperes when RCVR-

XMTR STATUS

2-13