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I marked all the good / bad ROMs. Yeah those new old stock 6550s are cool but too expensive for my pocket! I'll have a think about the other RAM options. "When you get to RAM testing I recommend using PETTESTER as it has an extensive MARCH RAM test which should give you confidence in the...

Many thanks for the really helpful advice! The cassette belt had perished so i bought a belt from an ebay seller which had a similar thickness and I best guessed the length - it seems to work ok. Using Vossi I tested the RAM; now i thought I had a decent set (I did the video ram swap...

Basically H3 and H5 are suspected dead! unless they are crappy sockets? or something else.

Hi Nivag, sry for the delay; H3 remains constant but H5 checksum will keep changing every few seconds.

So I got a PET the other year from Ebay (the PET was our first family computer); it was sold as faulty and so I decided to have a go at repairing it. I did a few things to it and then just ended up getting a RAM/ROM replacement (ROMulan v4.1) to get it up and running. I didn't really do...

I must confess after reading those posts I do feel a bit lazy now just stuffing in a RAM/ROM replacement to get mine working. I think i'll create a new thread and see if I can diagnose the issues with my board; and I have another PET board which I managed to pick up as a potential donor...

I've just been reading over some of the past PET repair threads - wow some of them have been a real rollercoaster ride to follow! packed full of really useful info! And your diagnostics ROM project code is really useful!

Ah ok, in that case you'd fly past the turning for the M55 which would lead you to the home of a PET 2001-8, 320008. There's a nice coffee shop in Lancaster - me and the missus were there at the weekend getting some supplies. A strong coffee helps me not put my IC in the wrong way round!

Hi Sam, I bought a PET 2001 the other year that presented the same issue. I bought a ROMulator and switched out the ROMs (no luck) then tried switching out the ROMs & RAMs, and it booted up. This is only a guess but If the ROMulator is working correctly it looks like the CPU can't clear the...