A1200 Keyboard Problem - common causes?

CDTV1991 · 07 January 2012, 22:26

The vast majority of my A1200 keyboard does not respond. Before I undo the 250 tiny screws on the back of it can someone tell me if there are any common problems with these keyboards?

I can just about get 6 7 8 9 on the main keyboard and ( / on the numpad to respond?

No caps lock light

Can I test an A500 keyboard with it, or are the connections completely different?

roy bates · 07 January 2012, 22:42

it could be the cable that connects it to the motherboard a simular problem with old zx pectrum16k-48K boards the cable develops a crack in it and the traces inside get broken. or the carbon contacts are worn(sometimes this happens from spilling a drink on the keyboard)on the plunger on the keys themselves or the keyboard encoder is gone(you can find out this on by simply plugging in another 1200 keyboard if it works its the keyboard)

yes you can connect an a500 keyboard by wiring it direct to the 1200's keyboard encoder(cant remember how to at the mo but it's possible)yes they are wired differently the encoder's on the 500 keyboard.if you mean the ribbon i dont know never tried it.

Jope · 08 January 2012, 13:22

Most likely the problem lies in the contacts at the end of the ribbon cable.

Perhaps it's been pulled out of the connector without opening the latch a couple of times too many and it's just too worn out.

CDTV1991 · 08 January 2012, 22:20

The keyboard ribbon seems to have some thick transparent tape on it. I wonder if it has been repaired in the past?

I'm going to try and check the connections along the cable

Jope · 09 January 2012, 13:47

There is a thicker sheet of plastic glued to the end of the ribbon from the factory.

Retroplay · 04 December 2012, 14:22

Quote:

Originally Posted by Jope

There is a thicker sheet of plastic glued to the end of the ribbon from the factory.

Does anybody know a way to remove some of that glue without damaging the cable ?

My keyboard started acting up, so I had a look at the end of the ribbon cable and could see some of the traces are knackered.

I used an exacto knife and cut off 1-2 mm which did help as some of the faulty keys worked after that, but not all of them.

roy bates · 05 December 2012, 01:26

you can peel it back if your very carefull,a bit like the spectrum 16k and 48k membranes.

Retroplay · 05 December 2012, 15:11

Thanks I'll give it a (very careful) go later then.

Why couldn't they just have sticked to a wired connector as in an A500..

07 January 2012, 22:26	#1
CDTV1991 Registered User Join Date: Feb 2011 Location: Wales Posts: 279	A1200 Keyboard Problem - common causes? The vast majority of my A1200 keyboard does not respond. Before I undo the 250 tiny screws on the back of it can someone tell me if there are any common problems with these keyboards? I can just about get 6 7 8 9 on the main keyboard and ( / on the numpad to respond? No caps lock light Can I test an A500 keyboard with it, or are the connections completely different?

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07 January 2012, 22:42	#2
roy bates Registered User Join Date: Apr 2011 Location: birmingham Age: 55 Posts: 2,827	it could be the cable that connects it to the motherboard a simular problem with old zx pectrum16k-48K boards the cable develops a crack in it and the traces inside get broken. or the carbon contacts are worn(sometimes this happens from spilling a drink on the keyboard)on the plunger on the keys themselves or the keyboard encoder is gone(you can find out this on by simply plugging in another 1200 keyboard if it works its the keyboard) yes you can connect an a500 keyboard by wiring it direct to the 1200's keyboard encoder(cant remember how to at the mo but it's possible)yes they are wired differently the encoder's on the 500 keyboard.if you mean the ribbon i dont know never tried it.

08 January 2012, 13:22	#3
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,911	Most likely the problem lies in the contacts at the end of the ribbon cable. Perhaps it's been pulled out of the connector without opening the latch a couple of times too many and it's just too worn out.

08 January 2012, 22:20	#4
CDTV1991 Registered User Join Date: Feb 2011 Location: Wales Posts: 279	The keyboard ribbon seems to have some thick transparent tape on it. I wonder if it has been repaired in the past? I'm going to try and check the connections along the cable

09 January 2012, 13:47	#5
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,911	There is a thicker sheet of plastic glued to the end of the ribbon from the factory.

05 December 2012, 01:26	#7
roy bates Registered User Join Date: Apr 2011 Location: birmingham Age: 55 Posts: 2,827	you can peel it back if your very carefull,a bit like the spectrum 16k and 48k membranes.

05 December 2012, 15:11	#8
Retroplay Lemon Curry ? Join Date: Sep 2004 Location: Denmark Age: 49 Posts: 4,136	Thanks I'll give it a (very careful) go later then. Why couldn't they just have sticked to a wired connector as in an A500..

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