Introduction
I purchased this Atari 800XL locally. It was in decent condition and spruced up nicely after some scrubbing with 99% isopropyl alcohol (IPA). I did not know when I bought it whether it worked and was happy to see it boot right up to the Ready prompt with a healthy blue Atari screen. However, the “T” key was stuck on and typing across the screen.
Case Study
I have fixed enough keyboards now to suspect the mylar membrane needed to be cleaned. This is a CO61983 made in Taiwan. I first removed the case and unplugged the keyboard ribbon from the motherboard. The keyboard is screwed to the top piece. I removed the screws to free the keyboard.
Flipping the keyboard over reveals lots of time screws that hold the keys to the baseplate with the mylar sandwiched inbetween.
I then removed all the little screws are lifted the plate free exposing the mylar membrane.
I then carefully removed the mylar and wiped down all the surfaces inside and out with a microfiber cloth and some 99% IPA.
I assembled the keyboard and put it back in the case. This simple cleaning with IPA fixed the stuck key!
Comments
This was an easy fix. Likely just contacts fused together by grime. Sometimes the traces are broken or damaged resulting in a more frustrating repair or the need to replace the mylar. Fortunately, you can buy replacement mylars for these keyboards. See this one from 8-Bit Classics. You can also find new keyboards as well.
Here is an AtariAge post about the keyboard variants for the 800XL.