B&K Precision 1795 - Manual - Manual (Page 15)

5.3.6 If Fuse blows, connect the unit through a variable AC Source with a current meter
and monitor the current at no load. If the current is very high (more than 2 ampere
or so ) load, check for Bridge Rectifier short or shorted Diode, or Secondary
Winding short, etc
5.3.7 If output voltage or current DPM's are not reading, check for loose connections
especially in crimping, soldering, of Connectors.
WARNING
THE FOLLOWING SERVICING INSTRUCTIONS ARE FOR USE BY
QUALIFIED PERSONNEL ONLY.TO AVOID PERSONAL INJURY, DO NOT
PERFORM ANY SERVICING OTHER THAN THAT CONTAINED IN
OPERATING INSTRUCTIONS UNLESS YOU ARE QUALIFIED TO DO SO.
REFER TO OPERATORS SAFETY SUMMARY AND SERVICE SAFETY
SUMMARY PRIOR TO PERFORMING ANY SERVICE.
5.4 VOLTAGE & WAVEFORM CHECK POINTS :
5.4.1 TEST EQUIPMENTS REQUIRED : Generally, Wide-band Oscilloscope
20MHz Dual Trace, a probe 1:10 / 50MHz, and a multimeter 4½ DMM, Rheostats,
Variable Line Source 30A, Test Leads are all that is needed to perform basic
waveform and voltage checks for diagnostic pusposes.
CONNECT THE MAINS CORD OF THE UNIT TO THE RATED I/P SOURCE.
5.4.2 Check the voltage & waveforms at test points TP1 to TP6 on PRSR 0896 PCB
with respect to output positive or at TP7 with the help of 4½ DMM & CRO. Normal
voltages & waveforms are given below :-
Keep output voltage to max. position with front panel control. All readings
are with respect to TP7 as common :-
Test Points on Voltages on AMP/FREQ. WAVEFORM
PRSR PCB DMM Level on CRO on CRO
TP1 +12.01V 26.7V P-P / 99.8Hz
TP2 +1.03V 2V P-P / 99.8Hz
TP3 -12.04V 26.8V P-P / 99.6Hz
TP4 -11.35V 25.3V P-P / 99.6Hz
TP5 +0.101V 3V -P / 99.6Hz
TP6 +15.05V 26.8V P-P / 99.6Hz
12