Dirty Spectrums

rwap

I have a Spectrum+ computer which has come from a smokers house unfortunately.

Although coated in nicotine (I hate to think the state of their lungs if the Spectrum is in this state), it works to an extent.

However, some of the keys do not work - EXTEND MODE, SYMBOL SHIFT (left hand one), " and <- key (from memory). I have tried a different membrane, and even a different keyboard top, but to no avail.

I presume that one of the pins on the molex connectors is therefore very dirty - any suggestion which one as they are not easy to clean!

georgedb

alcohol? specific cleaner for contacts?

you could also try to see if it really works, or that something on the pcb is broken, by using a piece of wire, as both connectors just form a matrix for all keys.

actually i can't iamgine that the new membrane doesn't work because of a bad contact, as the connectors are hold pretty tight in the connectors...

BloodBaz

EXTEND mode key is a mixture of SYM SHIFT and CAPS.
Quote (") key is a mixture of SYM SHIFT and 2 key
Therefore SYM SHIFT key is the common demonator.

The thing is, as every key comprises of 1 line on the 8 pin molex with 1 line on the 5 pin molex, if one of those lines were dirty, I would expect a whole HALF ROW to fail (if one of the 5 pin lines was damaged) or 8 Keys across different half rows to fail (if one of the 8 pin lines were damaged).

The common problem that you mentoned was SYM SHIFT.

• SYM SHIFT shorts the (left most or right most) line on the 8 pin molex with the (2nd from left or 2nd from right) pin in on the 5 pin molex.
• SYM SHIFT shares HALF ROW with SPACE, M, N and B (if all those fail, then it will be the right most or left most pin of the 8 pin molex that is faulty)
• SYM SHIFT shares COLUMNS with L, O 9, 2, W, S and Z (if all those fail, then it will be the 2nd or 4th line of the 5 pin molex that is faulty)

Hope this helps.

BloodBaz

PS: The Keyboard Scanner on [post=259717]this post[/post] may be useful (available in Z80 and TZX).