Service
Model
83522A
To troubleshoot the plug-in keyboard matrix, initiate the Key Code Test. Enter
SHIFT
O
4
.
Thereafter, when pressing any plug-in front panel key, the
appropriate hexadecimal key code should appear in the mainframe
FREQUENCYITIME display window. The appropriate key codes are given in
Table 8-6.
If this test indicates further troubleshooting, remove the front panel to make
A2
accessible while connections between the front panel, plug-in, and mainframe
are still intact.
If the numerical display is blank, check power supplies on
A2.
Check U6, pin 3, for the 200 kHz SCAN CLK signal. If it is missing, trace the
problem back through U4B to the A3 Digital Interface assembly.
Initiate Hex Data Rotation Write and check the L FP2 line for activity:
SHIFT
0
0
Hex Data mode
2
MHz
ms
8
0
Address location 2d00 (U6)
M4
Hex Data Rotation Write
The data line inputs should also be checked in this mode. The pattern should
match that shown in Figure 8-2.
Check the COLO through COL3 lines for sequential low pulses, as shown in
Figure 8- 14.
If the patterns are absent, but the 200 kHz clock is present, the problem is
probably U6. Ensure that problems in U4B or the
A1 assembly are not tieing the
lines down.
If the column strobes are present, probe both the column and row line
corresponding to the key in question at U6. Observe the traces while pushing the
button. The two lines should track each other. If they track, but the
microprocessor can't read the codes from U6 and the data bus is good, the
problem is probably in U6.
If row and column do not track, separate the
A1 and
A2
assemblies and
troubleshoot the keyboard matrix with a continuity tester.
Rotary Pulse Generator (RPG)
The RPG is a means of converting rotational information into digital signals
which can be read by the microprocessor. The hardware components needed to
decode the plug-in RPG (counter and sign latch) are located on the
8350A
A2
Front Panel Interface assembly. Some failures which appear to be in the plug-in
RPG,
(e.g., 'run-away' POWER display or a locked-up sign) are likely to be
caused by failures in the
8350A.
If the plug-in RPG appears to be dead, remove the bottom cover of the 8350A
and probe AlOJ1, pins 34 and 36. Check for the waveforms shown in Figure 8-15,
while slowly rotating the RPG. If the signals are present, trace the PIRPGA and
PIRPGB lines through the
8350A to the mainframe
A2
assembly. Refer to 8350A
A2
Service Sheet for more information.
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