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Section V
Model 654A
d. The ac voltmeter indication should be 0.1V rms or
greater, verifying an output of at least 0.1V rms
into 50 ohms.
e. If the
limits
are not met troubleshoot the
instrument.
5-38. ADJUSTMENT PROCEDURE.
5-39. The following is a complete calibration procedure for
the Model 654A Test Oscillator. These adjustments should
Figure 5-14. Location of Internal Adjustments
be performed only if it has been determined by the
Performance Checks that the 654A is not meeting its
specifications. Figure 5-14 shows the location of all internal
adjustments.
5-40. CALIBRATION PROCEDURE.
541. To remove the top or bottom cover, remove the two
retaining screws, slide the cover about 1/2 inch to the rear
and lift off. To remove the side covers, remove the two
retaining screws and lift off. To replace the covers, reverse
the procedure.
THE 654A CONTAINS HIGH IMPEDANCE, HIGH FREQUENCY CIRCUITS. CONTAMINATION OF
THE SWITCHES, CIRCUIT BOARDS OR TUNING CAPACITOR WILL CAUSE HIGH IMPEDANCE
LEAKAGE PATHS AND SUBSEQUENT DETERIORATION OF THE PERFORMANCE OF THE
INSTRUMENT. AVOID TOUCHING ANY OF THESE CIRCUITS WITH THE BARE FINGERS, AS SKIN
OILS ARE EXTREMELY CONTAMINATING. IF HANDLING IS NECESSARY, WEAR CLEAN
COTTON OR RUBBER GLOVES. DO NOT USE A PENCIL TO TRACE CIRCUITS IN THE
INSTRUMENT. GRAPHITE PENCIL LEAD IS AN EXTREMELY GOOD CONDUCTOR AND AN
ACCIDENTALLY INTRODUCED PATH OF THIS TYPE IS SOMETIMES DIFFICULT TO LOCATE. TO
AVOID SURFACE CONTAMINATION OF A PRINTED CIRCUIT OR SWITCH, CLEAN WITH A WEAK
SOLUTION OF WARM WATER AND MILD DETERGENT AFTER REPAIR. RINSE THOROUGHLY
WITH CLEAN WATER AND ALLOW IT TO DRY COMPLETELY BEFORE OPERATING. DO NOT
APPLY ANY COMMERCIAL MOISTURE SEALING SPRAY TO THE BOARDS; APPLICATION OF
THESE AGENTS MAY CAUSE LEAKAGE PATHS.
5-12
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