TROUBLESHOOTING (Continued)

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. 2-44