exxos's Atari, Amiga & retro forum

Evening All.

I had a bit of time today working with one if my non functional Mega STs.

With a floppy connected and disk in the drive it would come up with 2 bombs. Did the same with a gotek fitted as well.

Today I socketed the MFP and YM and replaced them with new.

So now the Mega with a disk in will boot to desktop but shows all disks as empty. I have tried formatting a new disk and it goes through the format process and fails at the end.

I'm going to socket the DMA and Shifter as well as I intend to keep this Mega as it's in a pretty good condition otherwise.

Other things I've changed, WD1772, upgraded to 4mb, recapped psu, swapped GLUE for known working.

Just wondering where you all think I should look next?

Pull ups on the DMA data bus and 1772 buffer outputs... Both fixes done on the remake and documented in the tweaks and fixes section.

exxos wrote: ↑Sat Jan 19, 2019 7:56 pm Pull ups on the DMA data bus and 1772 buffer outputs... Both fixes done on the remake and documented in the tweaks and fixes section.

Cool, will try that tomorrow

well, surprisingly that fixed my other Mega, not the one I as expecting, LOL, as I did the patch to both.

The unfixed one still shows blank drives and doesn't boot to the UltraSatan but as I said, no the UltraSatan works great on the other Mega.

So one fixed fine, another to ork out hats going wrong. Will get everything else socketed and see how we go next.

Did you do both fixes?

exxos wrote: ↑Sun Jan 20, 2019 6:16 pm Did you do both fixes?

Yes I did both of them

Also bare in mind IMP DMAs need a diode in series with the 5v if your swapping those about. IMP are pretty evil.

exxos wrote: ↑Sun Jan 20, 2019 6:44 pm Also bare in mind IMP DMAs need a diode in series with the 5v if your swapping those about. IMP are pretty evil.

Fortunately no IMP on this board and the spare DMAs I have too are mostly not IMP. Got to be something daft as everything else works fine.

And yes, It was the DMA. Socketed it and swapped it for another and we are back in business with the Floppy and Ultrasatan

Forgottenmyname wrote: ↑Tue Jan 29, 2019 9:49 pm And yes, It was the DMA. Socketed it and swapped it for another and we are back in business with the Floppy and Ultrasatan

You little DMA killer you...