Service manual

34 Troubleshooting
NO
NO
YES
YES
START
"OV AT TURN-ON"
CHECK THAT THE OUTPUT VOLTAGE SETTING
IS NOT HIGHER THAN THE OV SETTING IN THE
MEMORY REGISTER. PROGRAM 0 VOLTS AND
MAXIMUM OV. THEN SAVE IN REGISTER 0
(PRESS THE SHIFT, SAVE, 0, ENTER KEYS).
TURN OFF SUPPLY.
CONNECT A DC SCOPE ACROSS THE OUTPUT
TERMINALS. TURN ON SUPPLY AND CHECK
THAT OUTPUT DOES NOT MOMENTARILY GO
HIGHER THAN THE VOLTAGE SETTINGS.
MOMENTARILY
GOES HIGHER?
GO TO "OUTPUT HELD HIGH"
TROUBLESHOOTING FIG. 3-6.
TURN OFF SUPPLY. REMOVE TOP COVER AND
RFI SHIELD. DISABLE THE OV INPUT BY LIFTING
A10R536. TURN ON SUPPLY AND CHECK
IS
OUTPUT
HIGH?
GO TO "OUTPUT HELD HIGH"
TROUBLESHOOTING FIG. 3-6.
NO
YES
OV STILL
OCCURS?
PROBABLE DEFECTIVE A10 BOARD
CHECK VOLTGES AT A10U521-7 84 ,
A10U502-12 70 , AND A10U502-14 63
YES
NO
DOES
A10U521-7
= +5.4 +/- 0.5 V?
YES
NO
IS
A10U502-12
> +0.5V?
YES
NO
IS
A10U502-14
HIGH?
WARNING:
DURING THESE TESTS THE OUTPUT MAY BE AT
HAZARDOUS LEVELS.
CHECK THAT A10U521-7 GOES FROM 0 V
IS PROGRAMMED FROM 0 TO MAXIMUM.
PROBABLE DEFECTIVE A10 BOARD
PROBABLE DEFECTIVE A10 BOARD
IF NOT, PROBABLE DEFECTIVE A10 BOARD
PROBABLE DEFECTIVE A10 BOARD
OR A9 DOWNPROGRAMMER BOARD
OUTPUT VOLTAGE.
WITH RESPECT TO COMMON 30
TO APPROX. 5.4 V AS OVERVOLTAGE
Figure 3-4. OV At Turn-On Troubleshooting)