... or how to figure something out while figuring something out
A few days ago, Mccnex/WantedTeam asked me to fix his spare Amiga 600 keyboards. I was like "Why not?! Send'em in."
The problem with this ZIF membrane connector is that it is covered with very thin, green foil layer. As seen on photos, someone already tried to remove this layer by sanding it off, however, failed miserably because underlying silver traces are super fragile. My first idea was to chemically remove that green foil. I've gently cut a small grove to remove foil easier while it's softened by chemicals.
Then another idea came - epoxy solvent.
It contains various hydrocarbons like Xylene for example.
This time, I've used Kapton tape to hold the membrane in place and to make sure that solvent will evenly cover treated area.
I've applied solvent and waited for a while. As I suspected, it started to soften a foil.
Since this job is kinda delicate and messy, I was really satisfied with an end effect. I've waited few minutes to let the solvent dry and started to remove Kapton tape .... aaaaand then the second hack was discovered lol.
While removing Kapton tape I've discovered that this thin, green piece of crap sticks to it and leaves nicely and evenly exposed silver traces.
Not the end
At this point, I was finally able to test keyboards.
After a quick assembly, one of the keyboards proved to be working flawlessly. Unfortunately, the other one was failing on keys "2 W S X" and "4 R F V".
My first wild guess was that one of a traces is broken somewhere but a naked-eye inspection didn't reveal a problem. I had to use a microscope and track whole trace to spot it. And I've found it.
Someone bent a membrane too much which caused a break.
A neat plan was prepared. I only had to join broken parts of traces with special conductive silver glue that I had in a drawer. The "only" part, proved to be quite hard to achieve. I've covered all intact traces with a tape and attempted to remove green foil with a previous "tape pull" hack.
This is how it looked.
The black spot was just to mark a broken trace.
Next, I've applied a silver glue on a broken trace. Since silver based glue cures itself at a certain temperature, I've started to heat it up with a desktop lamp - gentle option
That was quite a failure :D
It didn't work at all, so I've grabbed a HotAir blower and heated it a bit stronger :D
Finally, it worked and a glue cured.
Unfortunately, it appeared I wasn't super precise and a trace was a bit wider than I would like it to be.
Anyway, at this point, I could finish a job, but since I've spotted a nearly broken trace just next to first one, I've decided that I'll fix that one too.
Similar procedure was launched.
Both traces joined with silver glue.
At the end of a whole job, I've figured that it would be good to add an additional anti-bending protection. I've used a popular thick, rubbery-like door sealing tape to achieve it.
And that's it :) Two old keyboards were rescued from the Abyss ;)