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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Colday on December 09, 2023, 08:34:00 PM
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Good evening all.
I have recently obtained my first Amiga. A simple A500 with a normal expansion.
Machine boots up fine, using Workbench 1.3 and it boots to Workbench fine.
I ran the Amiga Test Disk (latest one from Github) and all seems fine till I run the keyboard test.
The whole board is fine till I hit f7. That then also showed that I had pressed the Help key.
Continued checking and found that the cursor keys also fired off the 'P' column of keys on the keyboard. I also noted that the '7' on the numpad hits the '-' key on the numpad.
As the title says I've done a lot of repairs on other old machines (you can find me on StarDot quite a bit as the old BBC's are my forte and nemesis), so I pulled the ribbon cables out of the decoder (it's a Samsung keyboard) and then used a jumper lead to fire off the keys singly via the keyboard matrix and I could get the keys to fire individually.
With this in mind I believe the membrane was a bit iffy, removed the keyboard screws and had a good look round, separated the top from the bottom (leaving the middle sheet of plastic to separate the two halves) and gave it a wipe over with some contact cleaner. It all looks fine. Put it all back together and it was exactly the same.
Does anyone have any ideas where to go next?
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First off. Welcome.
As for the issue you describe. It could just be a worn and ageing Membrane causing the issue. On the other hand it may also me a sign of the keyboard controller chip exhibiting a fault.
For me, I would attempt getting hold of a replacement membrane to try first. Plenty in EBay, but make sure it is for the Samsung keyboard. A lot of the keyboards were also made by Mitsumi.
Failing that, see if you can buy a replacement keyboard controller board. Plenty on EBay at around £6 second hand.
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I'm fairly happy it is not the decoder/controller board as when the membrane is unplugged I can fire the individual keys.
I've never come across the specific issue with membranes so is good to hear that it is common.
I'll grab a new membrane.
Thanks.
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No worries.
Common on all ageing equipment I’m afraid. Have had to change them in A1200 and A600 keyboards. 30+ years don’t help. 😉
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Ok, thanks for the help so far. The original supplier provided a Mitsumi keyboard which works fine, so with that in mind I want to buy a membrane for the Samsung.
Does anyone have a supplier for them as there are currently none on eBay.
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Yeah. Not sure on that one I’m afraid. Is the Samsung a Double tape membrane type? If not then can recommend this membrane which I always buy for any of my fleet that needs replacing…
https://sordan.ie/product/713/new-premium-hard-keyboard-membrane-pcb-amiga-500--1200-green/
It maybe you, might need to just acquire a Mitsumi keyboard as it may end up being cheaper than finding a Samsung membrane.