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2-4
Troubleshooting
Table 2-4 Troubleshooting by Symptom
Symptom
Single vertical line on the display
Single horizontal line on the display
No video
Dim video
No beep
No keyboard response
Raster but no video
Communication problems .
Vertical linearity
Possible Problem Area
1. Power supply voltages: +5, +12, -12, +15, +30, and +55
2. Dot clock circuitry
3. Custom IC H-Sync
4. Horizontal control circuitry
5. Yoke connection and horizontal signals
1. Power supply voltages: +5, +12, -12, +15, +30, and +SS
2. Dot clock circuitry
3. Custom IC V-Sync
4. Vertical controller circuitry
5. Yoke connection and vertical signals
1. Power cord, power switch, and fuse
2. Operator brightness and contrast control knobs setting
3. Power supply voltages: +5, +12, -12, +lS, +30, and +SS
4. Reset circuitry
5. Dot clock circuitry
6. Custom IC H-Sync, V-Sync, video 0, and video 1
7. Horizontal controller circuitry
8. Vertical controller circuitry
9. CRT driver
10. Voltage entering the yoke
1. Operator brightness and contrast control knobs setting
2. Power supply voltages: +S, +12, -12, +lS, +30, and +SS
3. VR204 setting (see Section 3, Adjustments and Alignments)
4. Adjustment of VR402 on the CRT driver (see Section 3, Adjustments and
Alignments)
1. Power cord and switch, fuse
2. +SV and +12V power supply voltages
3. Reset circuitry
4. Beeper circuitry
1. Power supply voltages: +5, +12, -12, +15, +30, and -t-55
2. Keyboard connector
3. Custom IC U4
4. Keyboard buffer U13
5. Keyboard PCB
6. 8032 IC U6
1. Operator brightness and contrast control knobs setting
2. Power supply voltages: +5, +12, -12, +15, +30, and +55
3. Custom IC video signal
4. CRT driver IC301 and 0402
1. Power cord and communications cables
2. Setup information incorrect for the host computer's requirements
3. Run the diagnostic test and look for error codes
1. Power supply voltages: +5, +12, -12, +15, +30, and +55.
2. Custom IC V-Sync
3. Vertical adjustment VR303*
4. Vertical controller circuitry•
•
See Table 3-2 for an illustration of this problem area.
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Table of Contents
Troubleshooting
