Service manual

Troubleshooting 33

START

"OV WILL NOT FIRE"

TURN OFF SUPPLY, REMOVE TOP COVER AND RFI SHIELD. TURN ON SUPPLY

VOLTAGES OK?

PROBABLE DEFECTIVE A6 BOARD

CHECK VOLTAGES AT A10U502-12 70 AND A10U502-14

A10U502-12

A10U502-14

YES

AND CHECK BIAS AND REFERENCE VOLTAGES (TEST POINTS 15

TURN SUPPLY ON AND PROGRAM THE OUTPUT

VOLTAGE AND CURRENT TO 1/2 SCALE. PROGRAM THE OV TO ZERO.

PROBABLE DEFECTIVE A10 BOARD

NEGATIVE?

LOW?

THROUGH 22 . SEE TABLE 6-3).

INSURE THAT OUTPUT VOLTAGE IS AS PROGRAMMED AND THE OVER-

VOLTAGE CONDITION IS NOT DETECTED (OV ANNUNCIATOR IS OFF).

63 WITH RESPECT TO COMMON 36 (See TABLE 6-3)

NOTE: U502-14 PULSES ARE LOW WHEN "OV" FIRES.

APPROXIMATELY 1 MILLISEC.LOW WHEN "OV" FIRES.

5 V

0 V

PROBABLE DEFECTIVE A10 BOARD

OR A9 DOWNPROGRAMMER BOARD

Figure 3-3. OV Will Not Fire Troubleshooting)