HP 3562A, Service Manual

Page: 464 / 570

S E RV I C E
MO D E L 3562A
8-1 4
4. To verify the device decoder PAL and buffer, use a logic probe to check the fol lowing
signals are the correct TTL level:
U303 pin 1 2 Toggling U401
1 3 Toggling
1 4 Toggl ing
1 5 Toggling
1 6 Toggling
1 7 H igh
1 8 Toggling
1 9 Togg l i ng
5. Press the H P 3562A keys as fol lows:
RETURN . . . . . . LOOP
OFF
LOOP
ON
p i n 2
7
1 0
1 1
T E S T
S O U R C E
Toggling
Toggling
Toggl ing
Toggling
FR E N D
I NTFCE
6. Use a logic probe to verify the fol lowing signals are the correct TTL level:
U303 pin 1 2 H igh
1 3 Toggling
1 4 H igh
1 5 H igh
1 6 Toggling
1 7 Toggling
1 8 Toggling
1 9 Toggl ing
7. Use a logic to verify the DS data l i nes are togging (FR END I NTFCE in loop mode).
Some of the li nes w i l l toggle slowly. Use the fol lowing test locations:
U406 pins 1 and 11 through 1 9
U405 pins 1 1 through 1 8
8. Press A2 S1 . After the power-u p tests are complete, verify the fol lowing signals are
the correct TTL level:
Test location
U203-2
U304-6
U304-9
U302-4
Signal Name
T E ST
N RSTL
BRST
R E S E T L
TT l level
Low
H igh
H igh
H igh
9. If the fault has not been found, go to part E.