IBM 5251 Series Maintenance Information Manual page 58

122
(continued)
F G
1
Replace the light pen feature card (125).
-
Press the I key (key position number 35) for each
line.
- Probe the following lines. Record any lines not at the
level shown.
Line Name
-reg 5 bit 1
-reg 5 bit 0
-reg 5 bit 2
-reg 5 bit 5
-reg 5 bit 3
-reg 5 bit 4
-reg 5 bit 6
-reg 5 bit 7
Pin
1-E-B03
1-E-B05
1-E-B07
1-E-B08
1-E-B09
1-E-B10
1-E-B12
1-E-B13
Level
Up
Up
Up (Down light
pulses)
Up
Up
Up (Down light
pulses)
Up
Up
Are all the lines at the level shown?
Y N
Power off.
- Disconnect the light pen feature card by
unplugging 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 at the correct 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' 1.0 MHz osc' line at 1- E- B02.
Is the line pulsing?
Y N
- Inspect the interposer.
- Replace the planar; set the jumpers correctly on
the new planar (103) (105).
- Inspect the interposer.
Replace the light pen feature card (125).
Suggested actk>n for an intermittent problem:
• Analyze the suspected line; inspect all of the
connector contacts.
• Replacement sequence:
- Light pen feature card
- Light pen feature assembly
Light pen power supply card
- Planar
1-40