IBM 5251 Series Maintenance Information Manual page 77

138
(continued)
- Check the' -power on reset' line at the planar.
Is the line at an Up level?
Y N
- Use MIM 141 to isolate the failure.
- Check the '+5 Vdc' and the' -5 Vdc' lines at the
planar.
Are the voltages correct?
Y N
A ground in the cable or keyboard could have
damaged the planar.
- Check for a grounded voltage line and then replace
the planar; set the jumpers correctly on the new
planar (103) (105).
- Check the '+5 Vdc' and the' -5 Vdc' lines at the
keyboard end of the cable.
Are the voltages correct?
Y N
- Check for an open voltage line in the cables.
- Check the' - DATA strobe' line at the planar.
Does the line pulse when a key is held down?
Y N
A
138
Is the '-DATA strobe' line at an Up level?
Y N
Disconnect the cable at the keyboard end.
Is the line at a Down level?
Y N
- Replace the keyboard logic PC board.
- Check the' - DATA strobe' line for a ground.
Is the' +DELA Y strobe' line Down at the planar?
Y N
- Replace the planar; set the jumpers correctly on
the new planar (103) (105).
- Check the' - DATA strobe' line at the keyboard
end of the cable.
A
Does the line pulse when a key is held down?
Y N
- Check the '+DELAY strobe' line for an open.
Inspect the -5 Vdc, the +5 Vdc, and 807
(' - DATA strobe' line) contacts on the keyboard
end of the cable.
Are the cables OK?
Y N
- Repair or replace the failing cable.
- Replace the keyboard logic PC board.
- Check the '-DATA strobe' line in the cables for an
open.
Are the cables OK?
1
N
- Repair or replace the failing cable.
Inspect the interposer.
- Replace the planar; set the jumpers correctly on
the new planar (103) (105).
- Disconnect the cable at the keyboard end.
- Check the '+DELAY strobe' line for a ground.
Is the line grounded?
Y N
Check the '+DELAY strobe' line for a ground at
the cable connector on the keyboard logic PC
board.
Is the line grounded?
Y N
- Replace the planar; set the jumpers correctly on
the new planar (103) (105).
Replace the keyboard logic PC board; set the
jumpers correctly on the new PC board (142).
Disconnect the cable at the planar.
- Check the '+DELAY strobe' line for a ground at the
planar.
Is the line grounded?
Y N
- Repair or replace the cable.
- Replace the planar; set the jumpers correctly on the
new planar (103) (105).
Maintenance Procedures 5251 MIM 1-59