Service manual

Troubleshooting 39
START
"SECONDARY DOWN"
DISPLAY READS "SECONDARY DN". TURN OFF SUPPLY
AND REMOVE TOP COVER. TURN ON SUPPLY AND CHECK FOR
SERIAL DATA PULSES AT A2U110-8 TEST POINT 5
WITH RESPECT TO PRIMARY GROUND 1 . (SEE TABLE 6-3).
PULSES
AT A2U110-8?
CHECK FOR 5V AT A2U110-8 WITH RESPECT TO SECONDARY
COMMON (A2U110-5) 12
5V AT
A2U110-8
CHECK FOR SERIAL DATA PULSES AT THE A10 CONTROL BOARD
CIRCUIT POINTS AS INDICATED BELOW WITH RESPECT TO
SECONDARY COMMON 12 .
PULSES
AT A10U506-10?
PROBABLE DEFECTIVE A2 BOARD
CHECK CABLE W4. CHECK
SECONDARY BIAS CIRCUIT TEST POINTS 20 21
AND 22 . (SEE TABLE 6-3).
CHECK FOR CABLE W4 OPEN.
NO
YES
NO
YES
NO
YES
PROBABLE DEFECTIVE A2 BOARD
PULSES
AT A10U504-11 AND
NO
YES
PROBABLE DEFECTIVE A10 BOARD
A10U505-14 ?
PROBABLE DEFECTIVE A2 BOARD
Figure 3-9. Secondary Interface Down)