IBM 5251 Series Maintenance Information Manual page 54

121
(continued)
BCD
B C
1
Power off.
- Disconnect the 2J cable at the 2J interposer.
Power on.
- Probe the failing line on the interposer at the 1 E
socket of the planar.
Is the line now at the correct level as shown
above?
Y N
Power off.
Disconnect the light pen feature card by
disconnecting the interposer at connector 1 E
and plugging it into the planar connector
only.
- Power on.
- Probe the failing line on the interposer.
Is the line now at the correct level as shown
above?
Y N
- Inspect the interposer.
- Replace the planar; set the jumpers
correctly on the new planar (103) (105).
- Replace the light pen feature card (125).
Replace the 2J cable.
B C
1
Press any data character key (grey key).
- Probe the '-reg 13 bit 3' line at 1-E-D11.
Is the line at an Up level?
Y N
- Power off.
1·36
Disconnect the light pen feature card by
disconnecting the interposer at connector 1 E
and plugging it into the planar connector only.
Power on.
- Press any data character key (grey key).
Probe the' -reg 13 bit 3' line at 1-E-D11.
Is the line at an Up level?
Y N
- Inspect the interposer.
- Replace the planar; set the jumpers correctly
on the new planar (103) (105).
- Replace the light pen feature card (125).
Probe the' -reg 13 bit 7' line at 1- E- D13 while
pressing several data character keys (grey keys).
Does the line pulse with any key?
Y N
- Replace the planar; set the jumpers correctly on
the new planar (103) (105).
- Inspect the interposer.
- Replace the light pen feature card (125).
The' - LNC' line is failing.
Replace the light pen feature card (125).
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