Service manual

Troubleshooting 35
START
"OUTPUT HELD LOW"
THE OUTPUT IS HELD LOW AND PROT IS NOT ON.
TURN OFF SUPPLY, DISCONNECT THE LOAD, REMOVE TOP
COVER AND RFI SHIELD. TURN ON SUPPLY AND CHECK BIAS
VOLTAGES (TEST POINTS 9 THROUGH 22 , SEE TABLE 6-3).
ARE
VOLTAGES
OK?
NO
YES
TURN OFF SUPPLY AND GO TO "A5 CONTROL BOARD TROUBLE-
SHOOTING SETUP" (TABLE 6-3). TURN ON SUPPLY AND PROGRAM
OUTPUT TO 1/2 FULL SCALE VOLTAGE AND CURRENT. PROGRAM
OV TO MAXIMUM, OCP OFF, AND ENABLE THE OUTPUT.
IS CC
ANNUNCIATOR
ON?
YES
NO
NO
YES
IS UNR
ANNUNCIATOR
ON?
USE DIFFERENTIAL INPUT OSCILLOSCOPE
TO CHECK FOR PULSES AT A10J511 62 ,
A10U602-9 52 , A10U600-10 56 , A10U607-1 51,
A10U604-8 59 AND A10U605-7 55 .
SEE CORRECT WAVEFORMS IN FIG 6-1.
IS TP 62
OK?
15V, 40KHz
NO
YES
SEE "FET TROUBLE-
SHOOTING" FIG 3-11
CHECK CV PROGRAMMING
LEVEL AT A10U513-6 39
DOES
TP 56
= -5V?
YES
NO
CHECK VOLTAGE CALIBRATION.
SEE APPENDIX A IN OPERATING
MANUAL.
PROBABLE DEFECTIVE
A6 BOARD
PROBABLE DEFECTIVE
A10 BOARD
CHECK CURRENT READING
ON FRONT PANEL DISPLAY
PROBABLE DEFECTIVE
A10 BOARD
CHECK CURRRENT
CALIBRATION
CHECK FOR SHORT
CIRCUIT IN OUTPUT
READS 1/2 F.S.
CURRENT?
40 = -5V ?
CHECK CC PROGRAM LEVEL
AT A10U514-6 40
NO
YES
NO
YES
DISPLAY
Figure 3-5. Output Held Low Troubleshooting)