PSU related Blitter issues (Atari STE)

[Maximilian]

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?

[sascha.springer]

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?!

[Steve]

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.

[sascha.springer]

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?

[sascha.springer]

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

[exxos]

Have you changed the bus pullups ?

[sascha.springer]

Have you changed the bus pullups ?

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

[sascha.springer]

Image of the mainboard:

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

[JezC]

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

[Tomswork]

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