exxos's Atari, Amiga & retro forum

Jumpers look ok, so at least that question is answered.

I have had red screens and bus errors when I've knocked the card and it's wobbled in the socket. I have 2 carts, one is in a case and doesn't do that. Might be worth having a close look at the cartridge socket and the alignment of the contacts, see if any are possibly out of alignment.

Also, whilst IPA is great, you might want to try DeOxit or Electrolube on the socket, it may well have a layer of oxide that is causing poor contact.

With regards to testing the Blitter, I'm not sure how much it'll help to use the diag cart, it'll really depend on what the error messages say.

Do you have another machine you can test the cart on? I know it may not be an MSTE but it might give some clues why it doesn't work.

It is odd though that YAART works and nothing else. It would imply the ROM lines and databus is working, but maybe as only one selection works in the address space, maybe there is a bad connection on one of the address lines on the cartridge port. Might be worth re-soldering the port to see if that solves the problem.

Ok, so I did a few more tests:

- I tried Steinberg's DX/TX7 software on the MegaSTe and even with the cartridge in the port, I got a "No Key" dialog. This one worked fine on my STe, so I guess that confirm there's an issue on the Mega

- As asked, I tested the diagnostic cartridge on another machine, my 4 meg STe, and the ram, rom, timing, blitter, etc... tests seem to be working fine

Based on that, and the fact that the memory test on the cartridge did work on the MegaSTe, I guess it could just be one specific address line having a problem somewhere.

Can I somewhat do some continuity testing between the pins of the expansion bus and the pins on the CPU, see if I get a proper signal on all of them?

Dbug wrote: 24 Sep 2021 14:14 Can I somewhat do some continuity testing between the pins of the expansion bus and the pins on the CPU, see if I get a proper signal on all of them?

I think the cartridge has enough pad area you to insert the cartridge and use the pads for one probe, and indeed check those lines to the CPU or something..

I measured the voltage on the molex connectors, and I do have a clean 5v and 12v voltage.

But when I check the +5 VDC on the expansion bus, I get 2.73 volts, am I doing it wrong or does that look like a problem (same value if I use the pin 39/40 gnd instead of the shield on the motherboard, but was easier to take the photo with only one hand taken :D)

Dbug wrote: 24 Sep 2021 14:14 Can I somewhat do some continuity testing between the pins of the expansion bus and the pins on the CPU, see if I get a proper signal on all of them?

Did you try re-flowing the solder on them first? This would be the first thing you'd want to rule out

Dbug wrote: 24 Sep 2021 14:53 But when I check the +5 VDC on the expansion bus, I get 2.73 volts

Looks like you are onto something there then..

@Dbug On the MSTE Schematic it looks like you might want to check F21 & L204? Perhaps the capacitors C229 C230 could also be defective... I don't know if it is possible that the fuse has 'half blown' and is acting as a resistor? Perhaps check it's resistance...

edit: Just thought, check VCC *before* the fuse F21 to see if the problem is before or after.

Dbug wrote: 24 Sep 2021 14:53 I measured the voltage on the molex connectors, and I do have a clean 5v and 12v voltage.

But when I check the +5 VDC on the expansion bus, I get 2.73 volts, am I doing it wrong or does that look like a problem (same value if I use the pin 39/40 gnd instead of the shield on the motherboard, but was easier to take the photo with only one hand taken :D)



image_2021-09-24_155058.png

That may be your problem, I have 5.02v at the same point on my diag cart, though mine is different to yours. I'd check it on the MSTE with no cart fitted, then you can work out if it's cart side or MSTE side.

Steve wrote: 24 Sep 2021 15:05 @Dbug On the MSTE Schematic it looks like you might want to check F21 & L204? Perhaps the capacitors C229 C230 could also be defective... I don't know if it is possible that the fuse has 'half blown' and is acting as a resistor? Perhaps check it's resistance...

edit: Just thought, check VCC *before* the fuse F21 to see if the problem is before or after.

Looks like you have stumbled upon something!

On one side of F21 I get 5.02


On the other side, 3.15


Now the question is, how do I find a replacement for this component, and do you think it's safe to temporarily "shunt" it with a wire to see if that fixes the issue?