TM 9-4910-663-34
Table 2-5. TROUBLESHOOTING (Continued)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 1.
Check to see that CIRCUIT BREAKERS CB2 DRIVE CONTROL, CIRCUIT BREAKERS CB3
BLOWER, and CIRCUIT BREAKERS CB4 BLOWER circuit breakers are all set to ON position. Set
TACHOMETER RPM SELECT switch S36 to DIRECT DRIVE position, and set TACHOMETER RPM
PULLEY CALIBRATION control R35 to mid-range. Connect AC voltmeter (0-10 range) to calibration
jacks below TACHOMETER RPM meter M1. Set circuit breaker switch CB1 to ON position and start
varidrive. Increase varidrive speed to 6000 RPM at high speed head, as measured with hand-held
tachometer. Check to see that external AC voltmeter indicates approximately 2 volts,
TACHOMETER RPM meter M1 indicates approximately 6000 RPM, and both meter readings vary
when TACHOMETER RPM SELECT switch is set to CAL PULLEY position and TACHOMETER
RPM PULLEY CALIBRATION control is varied.
If external AC voltmeter indication is correct but TACHOMETER RPM meter M1 does not
indicate, replace TACHOMETER RPM meter M1. If neither meter indicates, proceed to step 2.
Step 2.
With varidrive operating at 6000 RPM at high speed head, check for 10 to 16 volt AC indication
between black calibration jack at right side of TACHOMETER RPM meter M1 (facing meter) and
terminal 2 of PC board assembly, using AC voltmeter.
If no voltage indication is obtained, replace tachometer generator B3. If voltage indication is
normal, proceed to step 3.
Step 3.
Stop varidrive and set circuit breaker switch CB1 to OFF position. Set TACHOMETER RPM
SELECT switch S36 to DIRECT DRIVE position. Using ohmmeter, check for continuity indication
between left calibration jack of TACHOMETER RPM meter M1 and terminal 7 of PC board
assembly. Then, set TACHOMETER RPM SELECT switch S36 to CAL PULLEY position, and check
for open indication between same points, using ohmmeter.
If either indication is not as specified, replace TACHOMETER RPM SELECT switch S36.
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