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TonyDuell · 5th Feb 2020, 8:27 pm

A couple of comments...

I think all PETs used a decoder IC to select the keyboard columns. It should be easy to find by tracing the connections back from the keyboard connector, some will go to a PIA/VIA IC, the others to the decoder IC.

Secondly, a lot of problems in PETs are caused by bad IC sockets. I have fixed several such machines with odd symptoms just by replacing all the (dubious quality) original sockets with good turned-pin ones. This is normally the first thing I do to a PET. It may not cure the fault, but at least you then know there is a 'real' fault to trace.

5th Feb 2020, 8:27 pm	#8
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,222	Re: Commodore PET 3016 A couple of comments... I think all PETs used a decoder IC to select the keyboard columns. It should be easy to find by tracing the connections back from the keyboard connector, some will go to a PIA/VIA IC, the others to the decoder IC. Secondly, a lot of problems in PETs are caused by bad IC sockets. I have fixed several such machines with odd symptoms just by replacing all the (dubious quality) original sockets with good turned-pin ones. This is normally the first thing I do to a PET. It may not cure the fault, but at least you then know there is a 'real' fault to trace.