TROUBLESHOOTING (Continued)

TM 9-4910-663-34 Table 2-5. TROUBLESHOOTING (Continued) MALFUNCTION TEST OR INSPECTION CORRECTIVE ACTION If open indication is obtained, replace switch S6. 8. DC VOLTMETER OUTPUT VOLTAGE METER CIRCUIT a. DC VOLTMETER OUTPUT VOLTAGE METER INOPERATIVE OR PROVIDES INCORRECT INDICATIONS DURING TEST OF EXTERNAL COMPONENTS. Step 1. Set circuit breaker switch CB1 to OFF position. Connect external 0-50 volt DC voltmeter to DC VARIABLE VOLTS OUTPUT binding posts, observing polarity. Set DC VOLTMETER OUTPUT VOLTAGE RANGE switch S12 to X5 position, and DC VOLTMETER OUTPUT VOLTAGE SELECT switch S11 to VAR position. Check to see that CIRCUIT BREAKERS CB2 DRIVE CONTROL circuit breaker, CIRCUIT BREAKERS CB9 DC VAR. VOLTS circuit breaker, and CIRCUIT BREAKERS CB7 AC VAR. VOLTS circuit breaker are all set to ON position. Position DC VARIABLE POWER SUPPLY 0-32 VDC control T5 to fully counterclockwise setting. Set circuit breaker switch CB1 to ON position. Set DC VARIABLE VOLTS switch S10 to ON position, and adjust DC VARIABLE VOLTS 0-32 VDC control for 5 volt indication on external DC voltmeter. Set DC VOLTMETER OUTPUT VOLTAGE RANGE switch S12 to X1 position, and check to see that both external DC voltmeter and DC VOLTMETER OUTPUT VOLTAGE meter M2 both indicate 5 volts. If DC VOLTMETER OUTPUT VOLTAGE meter M2 fails to indicate, proceed to step 2; if indication is normal, proceed to step 4. Step 2. With control settings as in step 1, connect external DC voltmeter to calibrating jacks beneath DC VOLTMETER OUTPUT VOLTAGE meter M2, and check for 5 volts DC indication on both meters. If external DC voltmeter and DC VOLTMETER OUTPUT VOLTAGE meter M2 both do not indicate, replace DC VOLTMETER OUTPUT VOLTAGE SELECT switch S11; if external DC voltmeter indicates but DC VOLTMETER OUTPUT VOLTAGE meter does not, proceed to step 3. Step 3. Set circuit breaker switch CB1 to OFF position. Using ohmmeter, check for continuity between arm of DC VOLTMETER OUTPUT VOLTAGE RANGE switch S12 and terminal 12 of PC board assembly. 2-36