Model 4 - Keyboard problem

[volkoorn]

Three weeks ago I bought a TRS-80 Model 4 (264-1069, 64K, two disk drives, up/down arrow on left hand side, left/right arrow above the Enter key, German keyboard) on ebay which has not been used since at least 20 years. It's working fine (boots up with TRSDOS 1.3 as well as NewDOS 80) but the keyboard has some problem. Approx. 20% of the keys are working fine, e.g. the key 1-5, 7-0, but not 6. The letters W, J, V, M are working fine, but most of the others are not. ENTER and Break are good and from the numeric keypad only F3, 4 and Enter are working (don't know about F1 and F2). I've created a video demonstration https://www.dropbox.com/s/nm2yp55h6s..._1155.MOV?dl=0 to show the effect.

Does anyone has an idea what I can do to solve this issue? I hope that there is an easy way since I have to admit that my hardware skills are not so good.

Any help is appreciated.
Thanks!

[Patrick Bureau]

you need to open up the computer, disconnect it from wall power , unscrew the cover to the keyboard and flip it over to make sure the main board on the keybvoard doesn't have cracks/damage, it very common on older models to get a weight dropped on keyboard and it gets impaled by the center support.

Kinda looks like this at worst case scenario and yes fixable.

[Conats]

Here is a link to get you started:

http://www.halfbakedmaker.org/blog/post_id-5

I have done this to a few keys on my Model 4 with good results.

[Patrick Bureau]

and if you have that hold in the keyboard the repair is simple requires a little wiring and soldering skills. looks like this when fixed :

[volkoorn]

Hi Patrick, hi Conats,
thank you very much for your help. I will follow the hints during the upcoming weekend and send an update with the results I achieved.
Thanks again.