exxos's Atari, Amiga & retro forum

exxos wrote: 07 Feb 2021 23:12 This has all the signs of noise then... I'm not sure there will be a solution other than change the STE motherboard and start again. Diagnosing such faults can take a incredible amount of time and it pretty much always comes back to the bad grounding on the motherboard itself. Such faults appear quicker than I can diagnose them, it's why I gave up with it all and started with a new motherboard.

I wish I can find easily a new motherboard living in the US.. :/
At least, the good thing is, I am learning some electronics concepts. :)

geogeo_28 wrote: 07 Feb 2021 23:25 I wish I can find easily a new motherboard living in the US.. :/
At least, the good thing is, I am learning some electronics concepts. :)

ah :(

All I can suggest is go around every DMA pin with a 2.2K pullup resistors (on a fly-lead) and see if anything helps.. same with every pin and 33pF.. or 100pF see if you can find anything which helps or makes things worse.. Same with placing a 4700uF across the DMA, ROM, CPU.. its just endless trial and error unfortunately :(.

Hi!
After tweaking around with the DMA (C025913-38) by designing a small board and putting resistors, pull-ups, capacitors almost across all pins. Nothing solved my issue.

I was able to get a new DMA C025913-38 and identical results. Same signals on the scope. Still write issues at 8 MHz on UltraSatan...
Moving on, I ordered a DMA C398739-001A from Best Electronics and now reads/writes are rock solid on Floppy Disk (as before) but also on UltraSatan!

Meaning, yeah C398739-001A are more robust to the noise for sure. But....

The machine is completely unstable at 32 MHz, random crashes, data lines on the scope are pretty bad.
The irony is, switching back to C025913-38, rock solid at 32 MHz.

For sure, the board is noisy... I guess a nice project will be to transfer all the components to a clear/modern PCB remake of the Atari STE. :lol:

Now you know why I gave up with original machines :lol: :roll:

You are right at 1000%. :)

I managed to have a rock solid machine at 8 MHz and 32 MHz without any issue with Floppies and UltraSatan!


I simply used a thinner cable for the 32 MHz clock with a route far away as possible of the RAM (of course).


The only thing missing is to switch back to non-parity RAM and see how it goes.

But at the end of the day, I guess the DMA C025913-38 is doomed on some machines (with lot of noise on the data bus) and needs to be replaced by a C398739-001A.

I learned a lot tweaking around this Atari STE and I enjoyed it. Thanks exxos!

Cool! Did you not use / get a thin black wire in the booster bits ? You need to use that cable... I think someone posted how to route the cable, but cannot find it.. But it is shown in the guide anyway.

I received a white cable with the booster but a little too short to reroute far away from the RAM.
Yup I followed the guide how to route properly the cable. https://www.exxosforum.co.uk/forum/viewtopic.php?t=20

Hi all! I think I'm suffering the same "noise on bus" issues showing in the form of these "write protected" problems.
The machine seems to work fine, memory test went OK and PSU Recap.

The only issue I see is this problem writing anything on a floppy or formatting a floppy disk.

How can I confirm the issue and move forward with the fix?

Thanks!

Agv

andresv wrote: 17 Aug 2021 01:31 How can I confirm the issue and move forward with the fix?

Write protect can be caused by several things., the only way to confirm is to keep trying things until it's fixed.

Thanks for the quick response.
So, what would be the list of things to try?

Agv