Leaderboard

Hi I've just done a board with a broken IC pin. This pin was connected to pin1 of all the Eproms (m27c1001 type) which on the data sheets is labelled as "Program supply" first impressions seem obvious but does anyone know what's happening on the pins there? Is it like an enable or something like that? Thanks

lol its the programming pin, it sits supplied at 5v for normal reading, as it would be in a machine, but for programming it is raised higher, 13v for a amtel AT27c010 ( or whatever voltage is specified by the chip manufacturer for programming) and then once you have the address and data lines stabilized the /PGM pin 31 is taken briefly from 5v to 0v and back to 5v to program it, then the /OP pin 24 is taken from 5v to 0v so the data can be verified as being correct by the programmer and back up to 5v, once programming is complete the 13v is removed from pin 1 /VPP

You guys are amazing! Fuse replaced. Machine fully working once again. Big thanks!

Have you checked the 50v fuse on the PSU?

Cool! I understand that Andrew thanks... so that 5v not being present for normal reading will stop the program being read/ loaded? That's why this board wouldn't work. This board is an Epoch btw When I first read your explanation I thought the programming pin was for developing and programming the Eproms on the board (like wizard mentioned) but then I doubt the Actel chip would supply 13v? So this pin from the Actel chip is just for reading going to the Eproms? Hope I've got that lol. Maybe this is a good one to use for testing the Actel chip in the future then. Thanks hugely Andrew (and Ben lol!)

Thanks again to @MattyL on his great job on repairing the leg of the cpu on my epoch board, I can’t thsnk him enough.. before and after prices below

Haha thanks for the shout Ben. 😂🤞

Great news!

I've repaired this but just trying to understand how it works... If anyone can give me a lesson 😎

Might be an issue in the tube lighting circuits then.

My epoch only has 4 eproms so doesn't use that space

Thankfully, neither do I!

Can't believe your selling your best machine :(. It's better than all the rest by a mile (even though it's not working)