TB 9-6625-336-35
(4) Adjust differential voltmeter to measure ac voltage. Differential voltmeter will
indicate less than 5 mV rms.
(5) Connect differential voltmeter between ground and pink wire (fig. 2), using test
lead (B8). If differential voltmeter does not indicate between 5.6 and 6.0 V rms for Models
540B, CM77, and CM77A; or between 5.8 and 6.2 V rms for Model 640A, perform b(2)
below.
b. Adjustments (fig. 2)
(1) Adjust R73 for a differential voltmeter indication of 240 V dc for Models 540B,
CM77, and CM77A; or 225 V dc for Model 540A.
(2) Adjust R55 for a differential voltmeter indication of 5.8 V rms for Models 540B,
CM77, and CM77A; or 6.0 V rms for Model 540A (R).
13. Final Procedure
a. Deenergize and disconnect all equipment and reinstall TI protective cover.
b. When all parameters are within tolerance, annotate and affix DA Label 80 (US
Army Calibrated Instrument). When the TI receives limited or special calibration,
annotate and affix DA Label 163 (US Army Limited or Special Calibration). When the TI
cannot be adjusted within tolerance, repair the TI in accordance with the maintenance
manual. When repair is delayed for any reason or the TI cannot be repaired with local
resources, annotate and affix DA Form 2417 (US Army Calibration System Rejected
Instrument) and inform the owner/user accordingly in accordance with TB 750-25-1.
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