OJ’s projects…usually breaking stuff.

[olivier.jan]

Talking about PSU, I took a few minutes to build a quick one for the ST with parts lying around.
I still need to check the quality of the voltage, but it works fine so far (it doesn’t fix my issues though).

Now the question is: should I trust mor a40 years old Atari PSU directly plugged to main or a bunch of AliExpress parts quickly put together? This is very debatable….

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At least USB-C is much more convenient…

[olivier.jan]

Weekend progress: found a re-lacement GLUE (-38 instead of the original-20) and the 520 ST is now considered fixed. I’m still wondering what the problem is with the original GLUE as it works and pass tests from DIAG cart, the picture is fine in Mono but badly shifted in Low or Medium resolution. I will try to experiment with it in an H5.

In the meantime, I installed a 4MB RAM upgrade in an other 520 ST (slightly more recent). I installed the 4MB upgrade from Lotharek (Heron) and it was a bit challenging: not too much documentation, only documents are in Polish, but luckily we have translator software nowadays.

I had to remove the MMU socket and solder one part of the RAM upgrade, while the part goes under the shifter(mine was not socketed ), finally remove a bunch of resistors and the old RAM.
That was a lot of desoldering, moreover with the desoldering gun deciding to go on strike in the middle of the operation (might be a French one…).

Finally got a 4MB ST, took the opportunity to socket the CPU too in order to install a 16Mhz booster.
Didn’t have the opportunity to test the booster though: after removing the 10k bus resistors to replace it with 2.2k, I realized these early STs have 10 pin SIL resistors network instead of the usual 9 pins I have for my STFMs

Now I just need to wait for new 10 pins SIL to be delivered.

[olivier.jan]

Good progress on this little ST:
- Changed bus resistors with 2.2k … 10 pins resistors network.
- ROM changed to French and dual ROM(1.04/2.06) using 70ns chips (SST39SF020A)
- Installed the 16Mhz booster

Everything is ok so far, pretty good performances.

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Just need to add a switch for 8Mhz/16Mhz switching. Soldering/ unsoldering the cable each time is not a good long term solution.
A little tidying of the loose cable and the machine will be ready.

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[ijor]

Weekend progress: found a re-lacement GLUE (-38 instead of the original-20) and the 520 ST is now considered fixed. I’m still wondering what the problem is with the original GLUE as it works and pass tests from DIAG cart, the picture is fine in Mono but badly shifted in Low or Medium resolution. I will try to experiment with it in an H5.

Custom chips from the very first generation with the -20 suffix are pretty rare. Assuming that GLUE is not damaged it is very valuable for research purposes. Please make sure you keep it in safe place (hope is not too late and you didn't discard it).

Now, older GLUE versions have different vertical (not horizontal) timing. Conceivable, this could be confusing adapters calibrated for later GLUE versions. But, IIRC, this older vertical border is still present in GLUE-38. It changed with GLUE-38A. Exactly which one you have?

[olivier.jan]

Don’t worry, I rarely throw parts unless they are completely destroyed. The new glue is a -38 not a -38A.
Let me know if you want the -20 one, I can not guarantee it works ok as the color picture is heavily shifted (mono is perfectly fine).
I need to look for it in my drawers, it’s a bit messy at the moment, but as I replaced it recently it shouldn’t be too far down…

[olivier.jan]

Custom chips from the very first generation with the -20 suffix are pretty rare. Assuming that GLUE is not damaged it is very valuable for research purposes. Please make sure you keep it in safe place (hope is not too late and you didn't discard it).

Now, older GLUE versions have different vertical (not horizontal) timing. Conceivable, this could be confusing adapters calibrated for later GLUE versions. But, IIRC, this older vertical border is still present in GLUE-38. It changed with GLUE-38A. Exactly which one you have?

BTW, something I was looking for a few weeks back was a list of all the chips version of the ST with their specificities and compatibility. I started an excel spreadsheet with shifter information from various forums, but I don’t think there’s a centralized information source.

[ijor]

Don’t worry, I rarely throw parts unless they are completely destroyed. The new glue is a -38 not a -38A.

Interesting. That might mean that the -20 horizontal timing is different. I didn't have the chance to research this particular GLUE version. Conceivable it could be damaged, but not sure which kind of damage could produce that video shift and only in the color modes.

Let me know if you want the -20 one

Thanks a lot. In which part of the world are you located? Contact me by PM if you prefer.

BTW, something I was looking for a few weeks back was a list of all the chips version of the ST with their specificities and compatibility.

All the variants are supposed to be compatible with one another, but they aren't really 100% compatible. I made a thread about all the Shifter variants some time ago on atari-forum. The other chips have less variants and in general, have less compatibility problems. If you want the most compatible versions you should probably stick with:

GLUE & SHIFTER -38A
MMU & DMA -38

[olivier.jan]

Never ending story….
This morning I wanted to test the SF314 that came with the latest 520ST(C070243 rev I MB), didn’t work at first, opened it up, cleansed the head, greased the mechanical parts: we have a winner, worked like a charm.
So work on this machine was considered finished and I wanted to play a bit with it.
Plugged the ACSI2STM, nothing and floppy behaves strangely. Switched back to 8Mhz, same behaviour.
Plugged an external UltraSatan instead of the ACSI2STM, again nothing and floppy keeps seeking.

I guess just changing the bus resistors wasn’t enough, I will need to apply mandatory fixes related to DMA and 1772.

Now, I took the old 520ST and tried both ACSI2STM and UltraSatan, both works perfectly fine.
Plugged in the SF314… not working on this machine, with or without UltraSatan plugged in. So I guess, here too I will need more mandatory fixes. BTW, this machines is very very noisy, parasitic noise on the sound, crappy picture, don’t know if it’s because these older machines don’t have a cage around the shifter.

Anyway, at least the SF314 is now working. And I also took the opportunity to fully clean a recently received 800XL which had cartridge slots issues, it’s no 100% operational and looks gorgeous.

Enough Atari for today, will try the mandatory fixes on both STs tomorrow.

[olivier.jan]

Finally got some time today to have a look at the 520ST with ACSI issues.

I added some 10k resistor network on the DMA bus, still not working.

Changed the DMA IC with a known good one, still nothing.

I was ready to put the machine together and store it for later investigation when the desk light reflected on something inside the ACSI connector: One pin was bent and coming out of the back of the connector, shorting the 2 pins next to it.

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I had to remove the connector and actually multiple pins were having issues, moving back when an UltraSatan or ACSI2STM was plugged.

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I had to remove most of theses pins, clean the pins, open it manually and reinsert it. All this with abundant contact cleaner.

The 520ST is now fully functional but I m a bit scared of using the ACSI2STM, I suspect the square pins used for this build are not helping with the aging ACSI connector.

[exxos]

The 520ST is now fully functional but I m a bit scared of using the ACSI2STM, I suspect the square pins used for this build are not helping with the aging ACSI connector.

Square pins round holes...

Some of the pins I have seen used on that thing even though they are round, are simply too big for the sockets