MSX TURBO Keyboard repair

By fpracek

Resident (58)

fpracek さんの画像

19-12-2022, 09:44

One of my MSX TURBOs had a broken keyboard membrane.
After several attempts to fix it, I decided to change my strategy and I hope this post can help those in the same situation.
I bought some 6X6X12 mm buttons and I inserted them without the spring under each keyboard button. I rebuilt all the circuits with wires.
I soldered the leads on some 90 degree pin headers and inserted them into the motherboard contacts.
I attach some photographs.
It is also possible to directly solder the cables to the underside of the motherboard without having to remove the standard connectors if you don't want to use the pin headers.

The typing sensation is like that of a Sony HB-55P, a little different from that of the MSX TURBO, but in this way it is possible to solve the problem of membranes that no longer work.

https://imgur.com/jUvzNxi
https://imgur.com/hnydXob
https://imgur.com/L9dk41L
https://imgur.com/USMzuvq

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By Wierzbowsky

Guardian (3649)

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19-12-2022, 15:21

Wow! That's a tough job! But was the membrane so damaged that the silver-based glue could not fix it?

By fpracek

Resident (58)

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19-12-2022, 16:25

In my case the membrane closed the contacts but with a high Ohm value and probably the motherboard above certain values ​​considered the contact open.
I tried in a thousand ways, but I really didn't understand why the membrane behaved in this way.
After weeks of testing I decided on a drastic solution.

By Wierzbowsky

Guardian (3649)

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19-12-2022, 18:31

fpracek wrote:

In my case the membrane closed the contacts but with a high Ohm value and probably the motherboard above certain values ​​considered the contact open.
I tried in a thousand ways, but I really didn't understand why the membrane behaved in this way.
After weeks of testing I decided on a drastic solution.

Seen that too. It sometimes happens that a part of the track leading to the membrane's connector looses its connectivity and resistance raises from 50-60 Ohm to 1k or more. In this case the track stops working. To repair, you need to find the high resistance area and put some silver glue on top of it. Then wait for 15-20 hours to dry and measure the resistance again. When everything is done correctly, the track is back from the dead. Tried that several times already.

By usuario_msx2

Paladin (763)

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19-12-2022, 20:12

By fpracek

Resident (58)

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20-12-2022, 12:14

Thanks for your way. I will implement this way also! ;-)