HP 4262A Operating And Service Manual page 214

(B)——>|STOP _/~ A21U2pin?
Is
Signature at A21
U13 pin 8 CF87°?
CLOCK __/~ A22TP2
Is Signature of
+5V 0309 ?
+5V T2A7?
Is Signature Set 44*
OK?
CLOCK _/— A21U2pinl4
*See Table A
Press desired front NO
panel pushbutton. 3
Obs: i t ooy signal a Check A21U14, U24, Check 21013 Is Signature Set 45¥\NO Check A23U1
YES
Troubleshoot My YES _| Ul0, vl12,
U23, Ull an . OK? and UZ2.
Stuck Node ?
desired front panel
4 '
Stuck Node. and U22. If OK
pushbutton. Can a Check A2 4
15msec pulse wave- eck
A23U2. YES
*See service sheet 23.
NO ' form be observed?
15ms
Go to Flow Diagram B,
Check A21U2. l l
NO
Check keyboard
switch, A21U1
and U3.
Press LOCAL Is Signature Set 43 \NO [
Is Signature Set 42 \NO COLUMN Check keyboard
@—— pushoution. o_x{?j '\Ofy Bus Stuck? switch. -
YES YES
Nanoprocessor Check A21U11 Stuck Node ? Check A21U12 Troubleshoot
Data Bus Stuck? and U22. and U23. Stuck Bus.
YES
Troubleshoot ~ Troubleshoot
Stuck Bus. Stuck Node.
Figure 8-19. Digital Section Troubleshooting Procedures.
Flow Diagram H. A21 Board Diagnostic Flow Diagram.
Figure 8-19
Digital Section Troubleshooting Procedures
Flow Diagram G