IBM 5251 Series Maintenance Information Manual page 73

137
(continued)
Check the failing scan code line at the planar (the bit
line that did not change).
Press and release a key that activates the line.
Does the line pulse?
Y N
137
Is the line at a Down level?
N
'~
- Check the line in the cables for an open.
Are the cables OK?
Y N
- Replace the failing cable.
Replace the keyboard logic PC board; set the
jumpers correctly on the new PC board (142).
Disconnect the cable at the keyboard end.
Is the line still at a Down level?
Y N
Replace the keyboard logic PC board; set the
jumpers correctly on the new PC board (142).
Disconnect the cable at socket B on the planar.
Is the line still at a Down level?
Y N
- Repair or replace the failing keyboard cable.
Replace the planar; set the jumpers correctly on
the new planar (103) (105).
Inspect the interposer.
Replace the planar; set the jumpers correctly on the
new planar (103) (105).
Suggested action for an intermittent problem:
• Analyze the suspected line; inspect all the connector
contacts.
• Clean the pad PC board contacts.
• Replacement sequence:
Keyboard logic PC board
Planar
Keyboard cables
Maintenance Procedures 5251 MIM 1-55