IBM 5251 Series Maintenance Information Manual page 71

136
(continued)
- Check the failing line at the planar with the 10 jumper
installed on the jumper block.
Is the line at a Down level?
Y N
Check for an open line back through the keyboard
logic PC board.
Check the failing line at the planar with the 10 jumper
removed.
The line should be an Up level.
Is the line at an Up level?
Y N
Leave the jumper off.
Check the line from the planar back to the jumper
block on the logic PC board for a ground.
Is the line OK?
Y N
- Set the 10 jumpers correctly.
- Replace the cable or keyboard logic PC board.
Inspect the interposer.
Replace the planar; set the jumpers correctly on
the planar (103) (105).
- Set the 10 jumper correctly.
- Inspect the interposer.
Replace the planar; set the jumpers correctly on the
planar (103) (105).
Set the 10 jumper correctly.
Suggested action for an intermittent problem:
• Analyze the suspected line; inspect all the connector
contacts.
• Replacement sequence:
Planar
- Keyboard cables
- Keyboard logic PC board
Maintenance Procedures 5251 MIM 1-53