IBM 5251 Series Maintenance Information Manual page 50

120
(continued)
B
1
Enter several characters and press the Field Exit key.
- Place the light pen tip on the CRT at a displayed
character while probing the '- LP photocell' line at
2-F-D13.
Does the line pulse?
V N
- Check for a ground.
- Replace the light pen assembly (125).
- Probe the '-reg 25 bit 6' line at 2-E-D06 while
holding the light pen tip at a character on the CRT.
Does the line pulse?
V N
Is the line at a Down level?
V N
- Replace the light pen feature card (125).
- Inspect the interposer.
- Replace the planar; set the jumpers correctly on
the new planar (103) (105).
- Inspect the interposer for an open.
- Replace the planar; set the jumpers correctly on
the new planar (103) (105).
- No failure was found. If the problem still exists, use
the suggested action for an intermittent problem.
1-32
Suggested action for an intermittent problem:
• Analyze the suspected line; inspect all the connector
contacts.
• Replacement sequence:
- Light pen feature card
- Light pen feature assembly
- Light pen power supply card
- Planar