I was wondering if anyone has some suggestions. I have a TRS-80 model 4 with a membrane keyboard. The ribbon cable has two broken traces. Does anyone have any suggestion on how repair the ribbon? FYI, the ribbon cable is the same material as the
membrane in the keyboard, i.e. one big piece.

Thanks
David

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On Friday, November 11, 2016 at 4:11:45 PM UTC-6, David Jones wrote:

I was wondering if anyone has some suggestions. I have a TRS-80 model 4 with a membrane keyboard. The ribbon cable has two broken traces. Does anyone have any suggestion on how repair the ribbon? FYI, the ribbon cable is the same material as the

membrane in the keyboard, i.e. one big piece.

Thanks
David

I haven't done this, but depending on your skill level with soldering irons and such, it may be possible. it also depends where the foil trace is broken. You could take a x-acto knife to cut the membrane around the open trace and solder strands from a
small gauge wire and recover with heavy packing tape. Or you may be able to solder a piece of wire point to point from ckt board to connector. there are more possibles but I am tired of typing with one hand (broken arm). Post a pic and maybe a better
suggestion will show up.

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Well the plastic isn't Mylar so it melts pretty easily. But I'm going to try and solder it anyways and see what happens. At this point, it's ether that or see if I can use a conductive glue and solder a wire down. That is assuming I can expose the
conductors and get a good connection. Well my last resort idea is make a PS2 keyboard interface to the existing connector. I'm going to take it slow so I don't make thing worse.

A little more of the story. This was an ebay item that was supposed to be working. It wasn't completely. The video was out of adjustment and the power supply had bad solder joints on the connector. Both easy fixes. The worst was a mouse had chewed
on the lines going to the power switch and keyboard ribbon. That last item is the only thing that's been hard to fix.

David

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On Sun, 13 Nov 2016, David Jones wrote:

Well the plastic isn't Mylar so it melts pretty easily. But I'm going
to try and solder it anyways and see what happens. At this point, it's
ether that or see if I can use a conductive glue and solder a wire down.
That is assuming I can expose the conductors and get a good connection.
Well my last resort idea is make a PS2 keyboard interface to the
existing connector. I'm going to take it slow so I don't make thing
worse.

Be careful. My KIM-1 keyboard needed some work, and I tried to solder
around the problem, and melted the plastic or whatever it was. So be
careful.

Michael

A little more of the story. This was an ebay item that was supposed to
be working. It wasn't completely. The video was out of adjustment and
the power supply had bad solder joints on the connector. Both easy
fixes. The worst was a mouse had chewed on the lines going to the power switch and keyboard ribbon. That last item is the only thing that's
been hard to fix.

David

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On Monday, November 14, 2016 at 12:43:07 PM UTC-5, Michael Black wrote:

On Sun, 13 Nov 2016, David Jones wrote:

Well the plastic isn't Mylar so it melts pretty easily. But I'm going
to try and solder it anyways and see what happens. At this point, it's ether that or see if I can use a conductive glue and solder a wire down. That is assuming I can expose the conductors and get a good connection. Well my last resort idea is make a PS2 keyboard interface to the
existing connector. I'm going to take it slow so I don't make thing
worse.

Be careful. My KIM-1 keyboard needed some work, and I tried to solder
around the problem, and melted the plastic or whatever it was. So be careful.

Michael

A little more of the story. This was an ebay item that was supposed to
be working. It wasn't completely. The video was out of adjustment and
the power supply had bad solder joints on the connector. Both easy
fixes. The worst was a mouse had chewed on the lines going to the power switch and keyboard ribbon. That last item is the only thing that's
been hard to fix.

David

Yep, been there before too.

Well I just tried a small test solder and it was a no-go. The plastic just melted like I was afraid it would do. So back to the drawing board.

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Well I got the keyboard working. Below is what I did in case someone else runs into this problem

Took a X-acto knife and very carefully cut away the plastic over the trace that need to be repaired. I did it as close to the damage as possible and it also too some scrapping to expose the traces. It really helps if you have a hands free magnifying
glass.

Then I cut a piece of 30 gauge wire to fit, stripped the ends, then spot glued it down with super glue just short of the stripped part.

Once things were glued down so it wouldn't move around, I used some "Silver Conductive Paste Glue Wire Adhesive Paint PCB Repair For LCD 0.3ML USA" I got from ebay to make the connection from the original trace to the wire.

After this had dried and set, I tested the continuity. If it didn't take, rinse and repeat.

With the traces repair and tested, I then covered that section with thin cardboard pieces taped together. This was to keep it from flexing and popping the connections lose.

The only other problem I ran into was some cross talk once I tried it live in the computer. This showed up as if all the buttons on the repaired line were pressed. Turns out this was caused by the bracket that covers the cable as it enters the
motherboard cage. To fix that, I put a piece of thin cardboard between the cable and the bracket. Not sure why it only showed up on the repaired line but its all happy now.

Well I discovered two other problems with the computer. One was the focus pot on the video board was arcing. The other was the original floppy drives. The head rails need to be cleaned and lubed.

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