exxos's Atari, Amiga & retro forum

doc wrote: 28 Aug 2020 18:05
Well I'm really scratching my head :roll: . What the hell can it be ? I did all the test with exxos diagnostic cartridge and :
5 - DMA Port test says : D0 DMA time-out Fail at Cycle:000001 (may be it's normal)

The DMA test requires an additional test board that plugs into the 19 pin DMA connector, parallel port, and serial ports. So it will fail without the test board.

PaulJ wrote: 19 Sep 2020 21:58

doc wrote: 28 Aug 2020 18:05
Well I'm really scratching my head :roll: . What the hell can it be ? I did all the test with exxos diagnostic cartridge and :
5 - DMA Port test says : D0 DMA time-out Fail at Cycle:000001 (may be it's normal)

The DMA test requires an additional test board that plugs into the 19 pin DMA connector, parallel port, and serial ports. So it will fail without the test board.

Olivier sell that wire harness and board and built it on request. http://www.gossuin.be/index.php/shop#atariparts

DMA test cable may help, but as you are having issues with floppy and seems some odd RAM issues, it hints the DMA chip is damaged.. Though you may just want to change the DMA and 1772 before ordering more stuff anyway.. if that doesn't fix the problem, then I dont think the DMA test kit will really help anyway.

There are also some TTL chips and the MFP which may be at fault in all this as well..

I don't know what it is this week with all these odd floppy issues... Though its why I am moving to the H4/H5 boards as these faults are just appearing faster than I can diagnose them :roll:

Ok I give up. new DMA and 1772 Chips are too expensive.
Thanks for your help

doc wrote: 20 Sep 2020 20:20 Ok I give up. new DMA and 1772 Chips are too expensive.
Thanks for your help

I just spotted this whilst browsing and thought of this thread:

https://www.ebay.co.uk/itm/Atari-520-ST ... 4057308952

Hope this is okay me posting this @exxos :hide:

Thanks Exxos. i can give a last try as the DMA is not the more expensive compared to the WD1772. and if I’m a bit lucky I won’t have to change other neighbourhood circuits. In your opinion is the -20 fully compatible with the -38 DMA ?

I've never heard of a -20 DMA until now...

Like the one on the ebay url you post me : C025913-20
https://www.ebay.co.uk/itm/Atari-520-ST ... 4057308952

doc wrote: 21 Sep 2020 09:05 Like the one on the ebay url you post me : C025913-20
https://www.ebay.co.uk/itm/Atari-520-ST ... 4057308952

Hi @doc If you email the seller he'll probably know the answer. Really helpful guy. He talked me through an upgrade I was struggling with last year.

I think that seller also has/had a few IMP DMA chips available .. which might be better than the link (which claims to be for an STM only?)

:shrug: