Now that I'm done (for the moment) upgrading my 520STFM, I've decided to take a look at a 1040STF which I bought on ebay a few years ago, but which turned out to power up but not display anything and there's no flopy drive activity (no clicking, no access light).
This could be an ebay lemon (i.e. someone has stuck a ton of duff parts on a duff PCB and sold it), but I thought I'd have a quick go at seeing if the poor thing can be brought back to life as I'd hate to dump it or carve it up for parts.
So far I've checked basic voltages and I'm seeing +5V and +12V out of the main PSU cable to the PCB and +5V on the two red/blue cabling pairs which branch out from the PSU area to the other parts of the mainboard (tested at the far end). So PSU *seems* ok.
My main question: Beyond reseating the PLCC and DIP socketed ICs/cleaning contacts can anyone offer any advice or (hopefully) know of a general diagnostics guide for the Atari ST line. I.e. Check pin 15 of the CPU for the clock - which I'm going to do anyway, but serves as an example - etc.?
My plan of attack in the mean time is to:
- visibly check entire PCB for damage/corrosion
- check signals (CLK, RESET, R/W) and the buses to ensure nothing is being held hi/low permanetly or running in an indeterminate state.
I'm not sure I can do more than the above as my knowledge of of the M68000 and the ST architecture is near to zero (for the moment