4-10 Troubleshooting
Circuit gain
Table 4-1 summarizes the circuit gain factors for the various ranges.
Troubleshooting
Troubleshooting information for the various circuits is summarized below. Use the
“Principles of operation” on page 4-4 and the component layouts at the end of Section 6 as aids
in troubleshooting.
Display board checks
If the front panel DISP test indicates that there is a problem on the display board, use
Table 4-2.
Table 4-1
Circuit gain factors
Range Divider attenuation Preamp gain Multiplexer gain
100V 100:1 N/A X10
10V N/A X1 X1
1V N/A X1 X10
100mV N/A X1 X100
10mV NA X100 X10
Table 4-2
Display board checks
Step Item/component Required condition Remarks
1 Front panel DISP test. Verify that all segments
operate.
Use front panel display
test.
2 P1005, pin 5 +5V +/-5% Digital +5V supply.
3 P1005, pin 9 +37V +/-5% Display +37V supply.
4 U401, pin 1 Goes low briefly on power
up, then goes high.
Microcontroller RESET.
5 U401, pin 43 4MHz square wave. Controller 4MHz clock.
6 U401, pin 32 Pulse train every 1msec. Control from main proces-
sor.
7 U401, pin 33 Brief pulse train when
front panel key is pressed.
Key down data sent to
main processor.
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