Diagnosisng/repairing a PC Portable keyboard

[djfitzgerald]

I have an IBM PC Portable (5155). After a few months of it sitting unused, I turned it on and got a keyboard error code on POST. I booted it up, and ran diagnostics, and it appears that at a minimum the J and numeric pad 6 keys are stuck down. I want to know how to diagnose and possibly repair this.

I disassembled the keyboard using the instructions from the system maintaince guide, and didn't see anything glaring underneath the keycaps, although I will attemt to run a vaccum over it. I did notice that the stupid black foam is in place and has held form, but it dents and will fall apart if handled at all (and the bottom is sticky awfulness). I am aware that is to be expected with the foam materials IBM used in the early-mid 1980s. When I took the keyboard cover off, I did notice that the case was cracked (thankfully not broken) around each of the three tabs, leading me to suspect that its original owner also ran into some keyboard problems (and was heavy handed with his pry bar or screwdriver...).

What steps should I take to diagnose this problem? Any thoughts?

 

[WindShear]

If you haven't already you might want to fully disassemble it, clean it, and re-seat all of the switches. You said the foam is bad though, so I'm not sure if it would stand up to a full disassembly, or if maybe that bad foam is causing any of your problems. I got lucky with both of the ones I have and the foam was in decent condition.

Also there is a place where the controller PCB screws into the plate, make sure that is screwed in securely or it can cause what appear to be random keypresses if it moves around.