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Author Topic: Keyboard or Mainboard problem  (Read 5763 times)

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Offline freemac

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Re: Keyboard or Mainboard problem
« Reply #50 on: 10:29, 22 October 15 »
Hey all :) so I have a CPC 464 which boots up seemingly pretty well to a small HDTV I have (although a slight image wobble which I'll leave for now)


But the keyboard isn't entirely working.


The Caps lock, c, b, n, m, /, \, plus 2 and + on the numpad won't respond. According to the technical specs, this makes sense - one of the lines on the matrix of the membrane has expired.


I've opened up the 464 and given everything a good clean and looked at the membrane. It all looks intact, so I guess a new membrane is needed.


Does anyone know where I can get one? :)


In motherboard keyboard connection, there is a sort of paper behind, pushing more the contact area, this paper does lose weight over time. Just add a paper more...

Offline Bryce

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Re: Keyboard or Mainboard problem
« Reply #51 on: 10:44, 22 October 15 »
Hey all :) so I have a CPC 464 which boots up seemingly pretty well to a small HDTV I have (although a slight image wobble which I'll leave for now)


But the keyboard isn't entirely working.


The Caps lock, c, b, n, m, /, \, plus 2 and + on the numpad won't respond. According to the technical specs, this makes sense - one of the lines on the matrix of the membrane has expired.


I've opened up the 464 and given everything a good clean and looked at the membrane. It all looks intact, so I guess a new membrane is needed.


Does anyone know where I can get one? :)

464 Membranes are pretty robust. Check first whether it's really the membrane by bridging a wire between the non-working line (at the connector on the PCB with membrane dis-connected) to any of the contacts in the other keyboard connector. That way you can be sure where the problem actually lies. If the characters still don't appear, the problem is on the PCB (most likely the AY-3-8912).

Bryce.

Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #52 on: 12:15, 22 October 15 »
Sorry Bryce I am not that technical...what do you mean by bridging a wire? :( I don't have any equipment, just a screwdriver and some pliers!

Offline Bryce

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Re: Keyboard or Mainboard problem
« Reply #53 on: 12:32, 22 October 15 »
No problem, no fancy tools or technical knowledge required. At the connector you need to take a piece of copper wire and connect it as shown in the picture below. Start at the top pin of the left connector and connect this pin to each of the contacts in the right connector one after another. Each time you touch them you should get a character on the screen (although not in all cases). Then move to the second contact of the left connector and go through all right pins again. If any of the characters you're missing (C,B,N,M etc) come up, then the mebrane really is the problem.

Bryce.




Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #54 on: 15:13, 22 October 15 »
Thanks Bryce, I'll try to buy some wire from Maplins tonight and give it a go :)

Offline VincentGR

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Re: Keyboard or Mainboard problem
« Reply #55 on: 17:12, 22 October 15 »
I thought AY was controlling the keyboard on 6128 and on 464 was an intel chip  :-X
Can't remember correct.
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Offline TFM

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Re: Keyboard or Mainboard problem
« Reply #56 on: 19:02, 22 October 15 »
I thought AY was controlling the keyboard on 6128 and on 464 was an intel chip  :-X
Can't remember correct.


All CPCs have the same sound & keyboard chip, that way they are 100% compatible about that.  :)
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Offline TFM

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Re: Keyboard or Mainboard problem
« Reply #57 on: 19:07, 22 October 15 »
No problem, no fancy tools or technical knowledge required. At the connector you need to take a piece of copper wire and connect it as shown in the picture below. Start at the top pin of the left connector and connect this pin to each of the contacts in the right connector one after another. Each time you touch them you should get a character on the screen (although not in all cases). Then move to the second contact of the left connector and go through all right pins again. If any of the characters you're missing (C,B,N,M etc) come up, then the mebrane really is the problem.

Bryce.


I wrote an program to support this in an graphic way (see System Utilities), example here:


Keyboard Clash CPC6128 - YouTube

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Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #58 on: 23:45, 24 October 15 »
Bryce.


Hey Bryce, I haven't had the chance to test the keyboard as you suggest, but I have given the membrane a good clean and double checked everything else and it all looks fine, although I have noticed one of the connectors for the membrane's ribbons seems a very tiny bit loose on the motherboard, so I suspect it's that :(


Would you know who could repair it for me?

Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #59 on: 17:46, 25 October 15 »
Actually, forget that - found a wire today and tested, and I can get those missing characters up! So it must be the membrane then?


Where do I find replacements, folks? :)

Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #60 on: 01:27, 26 October 15 »
I think I have found the culprit having followed all the traces. All the faulty keys have one trace in common which gather into a single trace going into the ribbon that interfaces into the motherboard - and that trace has right at the end of the ribbon, a nasty scratch, on the black side.


How do I repair that kind of damage - silver paint as the other side, or something else?

Offline VincentGR

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Re: Keyboard or Mainboard problem
« Reply #61 on: 02:08, 26 October 15 »
I use "Silver Conductive Wire Glue Paste" to repair all kind of keyboards.
I even open a ZX+2 membrane in half to repair traces next to keys.
It works fine, it is elastic and drys almost instantly.
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Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #62 on: 12:06, 26 October 15 »
I use "Silver Conductive Wire Glue Paste" to repair all kind of keyboards.
I even open a ZX+2 membrane in half to repair traces next to keys.
It works fine, it is elastic and drys almost instantly.


So do I apply it to either side of the membrane or just to the silver side? The damage that I see is on the 'black' side of the membrane ribbon, not the silver side...

Offline Bryce

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Re: Keyboard or Mainboard problem
« Reply #63 on: 12:12, 26 October 15 »
The black side is where the conductor is, it needs to be added there.

Bryce.

Offline VincentGR

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Re: Keyboard or Mainboard problem
« Reply #64 on: 12:23, 26 October 15 »
As Bryce said.
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Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #65 on: 14:51, 26 October 15 »
Thanks, sounds weird considering people are telling me to get silver conductive and I'm ignoring the silver side :p

Offline VincentGR

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Re: Keyboard or Mainboard problem
« Reply #66 on: 15:06, 26 October 15 »
HAhHAHAAHAH
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Offline Bryce

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Re: Keyboard or Mainboard problem
« Reply #67 on: 15:20, 26 October 15 »
Explanation: The silver/carbon traces are black because they have oxidised. The other side still looks silver because the air can't get at it, you're looking at it through the plastic foil.

Bryce.

Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #68 on: 17:12, 26 October 15 »
Ah I see!


So do I need to open up the whole thing to double check, risking tearing, or just worry about the ribbon?


Sorry for all the questions.

Offline Bryce

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Re: Keyboard or Mainboard problem
« Reply #69 on: 17:39, 26 October 15 »
Ah I see!


So do I need to open up the whole thing to double check, risking tearing, or just worry about the ribbon?


Sorry for all the questions.

I'd just repait the crack you can see and then retest. If it works, then leave it at that.

Remember: If it's not broken, don't fix it.

Bryce.

Offline gladders

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Re: Keyboard or Mainboard problem
« Reply #70 on: 11:32, 29 October 15 »
I am glad to report that following a dab of silver conductant, another CPC 464 is back to full health :)


Thanks for your help!

Offline Bryce

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Re: Keyboard or Mainboard problem
« Reply #71 on: 13:43, 29 October 15 »
Congratulations, happy gaming.

Bryce.

Offline VincentGR

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Re: Keyboard or Mainboard problem
« Reply #72 on: 15:23, 29 October 15 »
Perfect!!!
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