Odd keyboard issue

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miked
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Odd keyboard issue

Post by miked »

Hi all

I've been working on my QL to solve a keyboard problem I've been having. It was originally that no keys on the keyboard would register at all. Having tried two new membranes it was obvious the machine was at fault. I've messed around changing all sorts such as the 8049 and 8302 and I've finally got the keyboard being recognised. I'm at the point where I can boot the machine and press F2 . At this point all the keys on the keyboard work apart from Space, Enter, arrow keys, ESC and \

Checking the keyboard layout, they are all keys on line 8 from J11. If I unplug the membrane and make a direct connection between line 8 on the J11 connector and line 9 on the J12 connector I get Enter. This works to produce all the keys which don't work when using the membrane.

I sent Rich at RWAP a quick email to ask if he had seen this before and he mentioned checking the pull-up resisters. I've taken off and tested R63, R64 and R67 and they all passed seemed to checkout. I think the one for line 8 on J11 is R63.

Does anyone have any ideas? I can't believe that two new membranes have exactly the same fault, so there has to be something amiss on the machine, but I'm not sure what to check now.

Cheers


miked
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Re: Odd keyboard issue

Post by miked »

Sooo, after much messing around I've fixed the problem. After much faffing around it came down to line 8 on J11 in the connector not being right enough. I looked at that damed connector so many times, but in the end I needed to insert a little paper behind the membrane going into the connector to apply a little more pressure and everything now works.

This has taken me WAY too long, but happy to have finally got it worked :)


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dilwyn
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Re: Odd keyboard issue

Post by dilwyn »

miked wrote:Sooo, after much messing around I've fixed the problem. After much faffing around it came down to line 8 on J11 in the connector not being right enough. I looked at that damed connector so many times, but in the end I needed to insert a little paper behind the membrane going into the connector to apply a little more pressure and everything now works.

This has taken me WAY too long, but happy to have finally got it worked :)
Well done!
Not sure if this would be the case for this particular QL - you often get problems of the keyboard connectors loosening up if a replacement keyboard has been used in the past, these sometimes come with thicker ribbon connectors and force open the connectors a bit (something I managed to do with a Keyboard Products Ltd keyboard which had a wire ribbon rather than a flat ribbon many years ago). Rarer but not unheard of is the connector opening up a little as membranes are replaced, loosening the connections. As you found, can often be corrected by inserting something insulated behind the ribbon to improve connection in a loose fit connector.


RWAP
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Re: Odd keyboard issue

Post by RWAP »

I did suggest checking if the pin had been pushed back, so glad it was an easy fix.

I have come across QLs where the molex connectors have indeed been forced apart (so much on one that you couldn't even keep the membrane in the connector when closing the lid) - however it is odd for just one pin to be affected.... Maybe whomever replaced the membrane in the past didn't clean the old bits of membrane out of the connectors properly and just jammed the membrane in anyway!

:D


Derek_Stewart
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Re: Odd keyboard issue

Post by Derek_Stewart »

Hi,

I have 5 QLs with the membrane connector contacts been forced apart.

I have tried to force the membrane contacts back to the normal position. But the "springyness" seems of been lost.

Probably needs new membrane connectors. But they are very hard to find.

I have removed each connector, maybe the internal contact can be replaced. This is the next course of action.

Would a new membrane connection be an idea.
Last edited by Derek_Stewart on Tue Mar 12, 2024 4:49 pm, edited 1 time in total.


Regards,

Derek
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Dave
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Re: Odd keyboard issue

Post by Dave »

This is not uncommon. Often, it takes as little as a too-entusiastic cleaning with a q-tip to push the spring clip back and cause a weak connection. I usually solve this by putting a bit of tape across the back of the membrane connector. That makes better contact AND reinforces it. I would have used paper, but someone once told me that plain paper is quite acidic and can cause the plastic to get crumbly over time.


RWAP
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Re: Odd keyboard issue

Post by RWAP »

Derek_Stewart wrote: Probably needs new membrane connectors. But they are very hard to find.

I have removed each connector, maybe the internal contact can be replaced. This is the next course of action.

Would a new membrane connection be an idea.
I have 5 sets remaining - http://www.sellmyretro.com/offer/detail ... puter-3807

Not cheap, but then to replace them I would need to order over 10,000 I believe it was....


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tofro
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Re: Odd keyboard issue

Post by tofro »

Doesn't necessarily need to be Molex, there is an alternative vendor:

http://www.tme.eu/de/details/ds1020-11s ... m/connfly/#

and

http://www.tme.eu/de/details/ds1020-09s ... m/connfly/#

At an incredible price of 4€-ct / piece... Minimum order 10

Hurry! Only 800 left of the longer ones...

Tobias

EDIT: Just realised they changed minimum order for the shorter ones to 1000, so maybe one wants to buy the angled version or cut a longer one for those.


ʎɐqǝ ɯoɹɟ ǝq oʇ ƃuᴉoƃ ʇou sᴉ pɹɐoqʎǝʞ ʇxǝu ʎɯ 'ɹɐǝp ɥO
RWAP
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Re: Odd keyboard issue

Post by RWAP »

They are cheap but you do need to add carriage and VAT (sent by courier, so expensive for a few connectors)

There are none of the shorter ones in stock - maybe someone grabbed them. Whilst you can cut down the longer connectors, the ends of the connector do help ensure the membrane is lined up properly :)


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Dave
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Re: Odd keyboard issue

Post by Dave »

Yeah, sorry about that. Supa sekrit skunkworks projekt! Cannot discuss (except all over here!)


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