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Old 21st Sep 2022, 10:14 am   #48
TonyDuell
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Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,191
Default Re: 1978 Commodore PET project

Quote:
Originally Posted by BrackenFix View Post
Do you have any recommendations for a logic analyser?
Firstly, I will say that when I was young and even more foolish than I am now, I thought a logic analyser (which no way could I afford then) would be the answer to all my prayers. When I did finally get a second-hand one (an old Gould Biomation K100D) I realised that while it's a very useful instrument, experience is worth a lot more.

I can only recomend the instruments I use on my bench, all of which are old. They are the Gould K100D (16 channels, 100MHz) which is enough for most work on older computers. The HP1630 which has rather more channels (but splits them between 'timing' and rather slower 'state' channels) which is the last HP series to have circuit diagrams in the service manual (that matters a lot to me) and the HP LogicDart, a handheld 3-channel instrument that is very convenient for quick checks.

There are many other excellent analysers available though. Some of the more modern ones are USB peripherals to a PC, I've heard good things about some of them but as I don't have a PC anywhere near my workbench they are not useful to me.

NEVER buy a logic analyser without the probes/pods. You will not find them separately, for just about every instrument the pods are much rarer than the unit itself. And they normally contain high-speed electronics (often as thick-film hybrid circuits) so making a reproduction is a major project, not something you want to do when you are starting out.

As for the PET, I notice your video RAM is 2114s. Those have much the same reputation with me as RIFA metalised paper capacitors. OK, they don't emit clouds of evil-smelling smoke, but they are not reliable. I regard them as 'replace on sight' and see if the problem goes away.

I'll second the recommendation for Cricklewood Electronics. I've bought many components from them without problems. In my case they are near enough for me to collect in person which is a major bonus.
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