UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Non-working Commodore PET 3016

SiriusHardware · 13th Apr 2021, 10:57 am

1) No, because it is loose conductive material which will end up deposited on the key contact fingers and hold keys permanently pressed. Just in the past week I have had two repairs where microprocessor boards had been disabled by someone who liked to press the reset button with a pencil. Result: PCB held permanently in reset by conductive graphite deposits.

2) No, because that sort of paint (meant for fixing PCB tracks) dries hard / brittle and will break up into fine conductive dust when it has been crushed a few dozen times, causing the same problem as above.

3) The least worst option because it is flexible and can take a bit of squashing. Not spray, because you can't control where it goes. It has to be paint, carefully applied with a fine brush. If you use that stuff you have to follow the instructions to the letter, in particular, you must mix it up properly and you must allow it to dry for the time specified.

I would try seeing if those dimples on the bottom of the key plungers can come off easily because if they do you have the option of trying to find an old PC keyboard which uses similar rubber-dimples-with-a-conductive-blob-attached.

13th Apr 2021, 10:57 am	#1585
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,548	Re: Non-working Commodore PET 3016 1) No, because it is loose conductive material which will end up deposited on the key contact fingers and hold keys permanently pressed. Just in the past week I have had two repairs where microprocessor boards had been disabled by someone who liked to press the reset button with a pencil. Result: PCB held permanently in reset by conductive graphite deposits. 2) No, because that sort of paint (meant for fixing PCB tracks) dries hard / brittle and will break up into fine conductive dust when it has been crushed a few dozen times, causing the same problem as above. 3) The least worst option because it is flexible and can take a bit of squashing. Not spray, because you can't control where it goes. It has to be paint, carefully applied with a fine brush. If you use that stuff you have to follow the instructions to the letter, in particular, you must mix it up properly and you must allow it to dry for the time specified. I would try seeing if those dimples on the bottom of the key plungers can come off easily because if they do you have the option of trying to find an old PC keyboard which uses similar rubber-dimples-with-a-conductive-blob-attached.