exxos's Atari, Amiga & retro forum

The question is what causes the issue:
1. Lower or higher voltage
2. Ripple
3. Voltage drop
4. Something else misbehaving due to the above.

Missing something?

Damn. After replacing my floppy disk drive with a Gotek device the issue is back. :shock:

I need to add that I have an IDE „backpack“ solution installed which works fine so far all the years. Probably I need another DMA hardware fix like the pull-up resistors on the bus?!

sascha.springer wrote: 23 Jul 2020 09:41 Damn. After replacing my floppy disk drive with a Gotek device the issue is back. :shock:

I need to add that I have an IDE „backpack“ solution installed which works fine so far all the years. Probably I need another DMA hardware fix like the pull-up resistors on the bus?!

Hi Sasha

In your first post you mention replacing your psu with a new psu - just to clarify, what was the new psu? A completely new model or a new old stock etc? I ask because if you replaced it with an original model, the caps could still be 30 years old.

And besides that I would recommend the DMA pullup fixes & re-cap your main board.

Steve wrote: 23 Jul 2020 11:08 Hi Sasha

In your first post you mention replacing your psu with a new psu - just to clarify, what was the new psu? A completely new model or a new old stock etc? I ask because if you replaced it with an original model, the caps could still be 30 years old.

And besides that I would recommend the DMA pullup fixes & re-cap your main board.

The PSU has been replaced with a completely new one.

Is there an overview of the caps on the mainboard to be replaced?

Today I checked when the issue appears after a cold start and with the new PSU it returns after about one hour.

Have you changed the bus pullups ?

exxos wrote: 24 Jul 2020 11:16 Have you changed the bus pullups ?

No, not yet. I‘ll have a look on the mainboard today if there is something suspicious.

Image of the mainboard:

RAMs (is the type a possible source of the issue?):

I think @exxos has posted in a few places that the ST/STE's can be fussy when SIMMs with parity are used...and if there are only the 3 chips on each SIM then I'm pretty sure the third is for parity.

So, there's a fair chance this will be one possible issue - I think you can just de-solder the third memory device (it's usually a different part number from the other two as it's a quarter of the memory capacity) - which might be the easiest course of action if you don't have any other spare memory available.

Certainly worth ruling this out before going for more drastic potential solution IMHO

There are three traces that can be cut on 30 pin parity simms. It is these traces to the socket that can cause a short

Edit

Pin 26 28 and 29 i believe

Tom