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Old 27th Oct 2021, 8:53 pm   #236
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,483
Default Re: Commodore PET 2001 voltage regulators

That board looks like it is intended to make 2764 / 27128 / 27256 / 27512 etc EPROMs 'look' like 24 pin PROMs as far as the host system is concerned. It won't look very pretty as there will be a 28 pin EPROM on a daughterboard overhanging a slot which should be occupied by a directly fitted 24 pin device, but you could take the view that looks won't matter when the unit's lid is on.

It does have the advantage that the 2764 and upwards are still widely available, whereas even 'standard' small EPROMs which don't have the abnormal pinout of the 2532 are getting slightly harder to come by, and as suggested earlier some of the popular cheap programmers include them in their supported device list but can't actually generate the correct VPP voltage.

I think if I was going to go the adaptor route I would use adaptors which convert 24-pin 2732 / 2732A - still relatively easy to get - to 24-pin 2532 pinout. Such adaptors are available if you look around, and then look for the 2732A to put in them because the cheap programmers are more likely to be able to get near their VPP of 21V than the 25V of the non-A versions.
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