Model 2701 Service Manual
Troubleshooting
4-13
Troubleshooting
Troubleshooting information for the various circuits is summarized below. See
“Principles
of operation” on page 4-5
for circuit theory.
Display board checks
If the front panel DISP tests show a failure, troubleshoot the display board using
Table 4-3
.
Power supply checks
Power supply problems can be checked using
Table 4-4
.
Table 4-3
Display board checks
Step Item/component
Required condition
Remarks
1
2
3
4
5
6
7
Front panel DISP test
P1005, pin 5
P1005, pin 9
U401, pin 1
U401, pin 43
U401, pin 32
U401, pin 33
Verify that all segments operate.
+5V ±5%
+37V ±5%
Goes low briefly on power up, then
goes high.
4MHz square wave.
Pulse train every 1msec.
Brief pulse train when front panel
key is pressed.
Use front panel display test.
D5V supply.
D37V supply.
Microcontroller RESET.
Controller 4MHz clock.
Control from main processor.
Key down data sent to main processor.
Table 4-4
Power supply checks
Step Item/component
Required condition
Remarks
1
2
3
4
5
6
7
8
9
10
11
Line fuse
Line voltage
Line power
+5VD pad
+3.3VD pad
+2.5VD pad
+1.8VD pad
U101, pin 7
U125, pin 3
U119, pin 3
U124, pin 3
Check continuity.
120V/240V as required.
Plugged into live receptacle, power on.
+5V ±5%
+3.3V ±5%
+2.5V ±5%
+1.8V ±5%
+37V ±5%
+15V ±5%
-15V ±5%
+5V ±5%
Remove to check.
Check power module position.
Check for correct power-up sequence.
+5VD, referenced to Common D.
1
+3.3VD, referenced to Common D.
1
+2.5VD, referenced to Common D.
1
+1.8VD, referenced to Common D.
1
+37V, referenced to Common D.
1
+15V, referenced to Common A.
2
-15V, referenced to Common A.
2
+5VRL, referenced to Common A.
2
1
U144, pin 2
2
C293 negative terminal
Summary of Contents for 2701
Page 15: ...1 PerformanceVerification...
Page 47: ...2 Calibration...
Page 70: ...3 RoutineMaintenance...
Page 78: ...4 Troubleshooting...
Page 97: ...5 Disassembly...
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Page 111: ...6 ReplaceableParts...
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Page 131: ...A Specifications...
Page 140: ...B CalibrationReference...