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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment. |
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5th Aug 2010, 10:52 am | #1 |
Triode
Join Date: Apr 2009
Location: Portsmouth, Hampshire.
Posts: 23
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Sinclair Spectrum ZX
I need help to fix this. It all works apart from the 1, 2, 3, 4 and 5 buttons. So I can't get it to do anything. Please help.
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5th Aug 2010, 11:21 am | #2 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: Sinclair Spectrum ZX
Sounds like a faulty keyboard membrane. 1, 2, 3, 4 and 5 are all in the same scan group. Check the 8-way connection. If you're very lucky, it will be nothing more than a dry joint where the connector meets the motherboard; if you're unlucky, it will be a crack in the membrane.
Replacement membranes do exist, but it's hardly worth sourcing one when you can make up an improved keyboard using tactile switches (available at very reasonable prices from the usual place).
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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
5th Aug 2010, 7:54 pm | #3 |
Retired Dormant Member
Join Date: Jan 2010
Location: Yorkshire, UK.
Posts: 293
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Re: Sinclair Spectrum ZX
If it's the part of the membrane that goes in to the board connector that's worn away, you can trim a little off the end of the membrane strip to enable a new part to reach into the connector.
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5th Aug 2010, 8:40 pm | #4 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
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Re: Sinclair Spectrum ZX
As has been said, the membranes were notorious for cracking across the tracks - they'e only conductive silver paint deposited onto plastic - and unless someone has already shortened the membrane connection before, you can trim a bit off with a pair of scissors.
But if that fails, new membranes for the original rubber-keyed spectrum aren't exhorbitant - eg, £8.50 and £2.75 P&P from this source, which can supply bits for other Sinclair PCs (ZX81, QL etc) and other makes: http://www.rwapsoftware.co.uk/membranes.html I'm not recommending this supplier, with whom I've had no dealings - I'm just pointing out one of many sources, and putting the cost of a DIY replacement membrane into perspective. Hope that helps. David. |
6th Aug 2010, 10:38 am | #5 |
Triode
Join Date: Apr 2009
Location: Portsmouth, Hampshire.
Posts: 23
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Re: Sinclair Spectrum ZX
Thank you for all your replies I will try this out and let you know.
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7th Aug 2010, 11:56 am | #6 |
Triode
Join Date: Apr 2009
Location: Portsmouth, Hampshire.
Posts: 23
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Re: Sinclair Spectrum ZX
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7th Aug 2010, 1:42 pm | #7 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: Sinclair Spectrum ZX
You can't solder to the membrane. But you should be able to force an offcut of Veroboard into the motherboard connector where the membrane plugged in.
What you'd have to do is, cut a piece of Veroboard to the right size and mount the switches on that at the correct spacing so you can use the original rubber keys to press on them (it's easiest to work "upside down", soldering them to the track side). The way these switches are made, they have two terminals connected to each switch contact, which makes the design a bit easier. There are 8 scan groups of 5 keys (half a row) each, and the column matrixing is done from outside to inside. The leftmost keys on each left-hand half-row are common with the rightmost keys on each right-hand half-row and so on, working inwards. If you need a diagram, I'll sketch one and scan it in.
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments. |
10th Aug 2010, 9:57 am | #8 |
Triode
Join Date: Apr 2009
Location: Portsmouth, Hampshire.
Posts: 23
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Re: Sinclair Spectrum ZX
Could you do that for me please? it would be a great help. I forgot to tell you that mine is a 48k + with the hard keys.
Last edited by Darren-UK; 10th Aug 2010 at 11:03 am. Reason: FSK. |