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Author Topic: New to Amiga, not to repairing old stuff  (Read 673 times)

Description: Keyboard issue

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Offline ColdayTopic starter

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New to Amiga, not to repairing old stuff
« on: December 09, 2023, 08:34:00 PM »
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?
 

Offline Boing-ball

Re: New to Amiga, not to repairing old stuff
« Reply #1 on: December 09, 2023, 09:41:52 PM »
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.
 

Offline ColdayTopic starter

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Re: New to Amiga, not to repairing old stuff
« Reply #2 on: December 09, 2023, 09:51:44 PM »
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.
 

Offline Boing-ball

Re: New to Amiga, not to repairing old stuff
« Reply #3 on: December 09, 2023, 09:55:23 PM »
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. 😉
 

Offline ColdayTopic starter

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Re: New to Amiga, not to repairing old stuff
« Reply #4 on: December 14, 2023, 08:01:16 PM »
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.
 

Offline Boing-ball

Re: New to Amiga, not to repairing old stuff
« Reply #5 on: December 14, 2023, 08:29:12 PM »
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.