HP 8112A Operating, Programming And Servicing Manual page 215

Troubleshooting
Note
Address Decoder
10.3-14 Servicing the Timing and
Slope Generators
•
If an error code is being displayed by the HP 8 1 12A you must press
a key,
for example, to return the microprocessor to normal
operation before troubleshooting.
•
The component layout and locator for the main board Al is at the
end of this chapter.
The address decoder UlOO can be checked with signature analysis.
Set the microprocessor to free run mode as follows:
1. Set the Pl wire on board A3
2. Disconnect Jumper A2W l .
3. Connect RES on A 3 t o ground for a short time t o ensure the
microprocessor is reset.
4: Connect the signature analyser ground to the microprocessor
board ground, then set the signal analyser as follows:
Signal A3 µP Board
Analyzer Connections
.r
Start TP "SA"
.r
Stop TP "SP"
\
Clock TP "E"
Ground Ground
5. Verify that the reading at the microprocessor board +5 V is 0003.
6. Check the signature of board inputs against those given in
Table 1 0.3-6
A3W4
Figure 1 0.3-7. Address decoder - Simplified block diagram
(
See Chapter 10.7) to position Pl.
LA3
LA4
LA5
U100
r- WS1
r- WS2
SRC
P I C
CLR
MAMO
W I C
D I C
LRC
RSA