It's weekend! Time to have a look at my 1040STF. I got it more than a month ago, and I don't even know if it's working. Shall we have a look inside?

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Well, I guess I'm going to void the warranty. 😅

Actually I think it's sad to damage the seal, but I have to open the case for a technical check and for the refurbishment.

Not too much filth has collected inside. But the keyboard is definitely in for a thorough cleaning.

I disassembled, cleaned, and reassembled the keyboard. It looks almost as good as new now. This is going to be a beautiful ST!

Now I will have a look at the PSU.

It's a Mitsumi SR98 PSU, which is said to be of poor quality. The filter capacitor is bulged, too. I could recap it, but I rather prefer to replace it with a modern PSU.

(⚠️ Caution: Electrical shock hazard! Do not open PSUs. High voltages may be present hours after disconnecting from mains.)

It's replaced with a MeanWell RD-35A, which has about the same power, and even has a closed frame. It fits so perfectly on the Atari frame that I assume the "A" in the model number stands for "Atari". 😆 I had to drill two holes into the Atari frame for mounting though.

If you try that at home, make sure to use correctly dimensioned wires, high quality cable shoes, and test that everything is grounded properly. Test it twice. At least.

The ST was sold as "untested, but the LEDs light up". Let's give it a test run, shall we?

Yay, it's working! 🎉

I don't know much about the ST, but the black Atari logo tells me that it's still the original ROM-TOS. So besides recapping the machine, I'll also need to do an upgrade to Rainbow-TOS.

To the Atari people: What TOS should I install on this 1040STF? As far as I can tell it should be V1.04. Or is there any advantage in installing V1.06 or V1.62?

I need HOW MANY 27C256 EPROMs? Six?? 😂

I have 5 on stock, and just ordered more. So no upgrade this weekend. But I have to wait for the floppy emulator anyway, it's also backordered.

Now for the standard procedure: Replace the capacitors with fresh, long-life ones. Mr Tramiel was also too cheap to put sockets into all six ROM slots, so I have to add sockets as well.

Done! All electrolytic capacitors are replaced. There are four new sockets waiting for the TOS EPROMs. Board is cleaned with IPA. Time for a final check. Then it's waiting for the delivery of the EPROMs and floppy emulator.

I even prepared the board for a Blitter chip, but when I saw the prices, I decided to better abandon this plan. 😅

It's still working. 🙂 So I'm done for today. The thread will be continued when the missing parts are here. I cannot wait to see the first demos running on that machine. Thank you for reading, and stay tuned!

The floppy emulator hasn't been delivered yet, but the EPROMs are, so I can still do a bit on my Atari ST today.

What I already did this week was completing the PSU. I printed a cable holder and a terminal cover. The wiring is now done, and it looks quite pretty.

I said that I had 5 EPROMs on stock. It turned out that they take a programming voltage of 21V, which my TL866II+ cannot provide. Luckily I ordered a set of old 27C256 EPROMs, so I still had enough left for burning. The ROM file was split into six images by my Pynaroma tool (

On the internet I only found tutorials about how to convert a machine from 6 ROMs to 2 ROMs. I have to do the opposite, so it feels a bit like I am driving counterflow. All I have to do is to change three solder pads from "1M" to "256K". Let's heat up the soldering iron!

What the… 😆 I found this after I pulled the original Hi-0 ROM from its socket. The "D3" pin has been bent all the time. It's almost a miracle that the machine has been working reliably all the years.

The EPROMs are seated, and the solder pads changed. I hope the machine is still working. 🤞

Hehehe... 😀 I guess this Atari ST hasn't expected to get a Rainbow TOS upgrade after more than 35 years.

So I'm already done for today. I hope the drive emulator will be delivered by next weekend, and I can finish the project.

The long awaited delivery from Centuriontech arrived today! I guess I can complete my Atari ST this weekend. 😀

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@shred I'm never sure about this. I kinda want to keep my machines as original as possible, but then again, PSUs are safety critical.

I wonder what the majority of the community thinks about this.

@rnlf I already had a dispute with someone who is repairing the PSUs instead. For me, the fun definitely stops when mains power is getting involved. An old and unmaintained PSU can also damage the computer. But I keep the original PSU in case I want to revert the change later.

@shred @rnlf 100% replace that PSU with a modern quality one. Tramiel Atari was notoriously cheap with components and construction

@48kRAM @shred That makes sense. I guess PSUs were always easy to save money on.

@shred Not in a straight ST. The "rainbow" TOS 1.04 should be fine. Unless you've installed a blitter.

@confusedbunny @48kRAM It should work, but from what I could find out it needs an adapter board or manual wiring. I guess I'll stay with TOS v1.

@shred @confusedbunny Theres no point though. 1.04 is the correct version for a straight ST

@48kRAM @shred But, yes, if it's not a drop in replacement probably isn't worth it.

@48kRAM @shred "fewest bugs, IDE support, memory check and most usable desktop" according to some forum post.

I have 2.06 on my MiSTer but haven't compared it to 1.04.

@48kRAM @shred Finally got around to comparing these. 1.04 boots quicker. 2.06 has loads of extra options in the menus, so GEM is much improved. The easy way to tell the difference is 1.04 has a solid green background, whereas 2.06 is dithered green (it's a lot easier on the eyes, and can be changed - back to solid green if you like)

@shred Yes. You can convert it to 2 chip TOS but it's invasive IIRC. Also you'll need a split high/low image set. DM me if you need images.

@48kRAM Thanks, but I already found the images, and splitting is not a problem. I know that from burning Amiga ROM images (although they need to be split from 32bit to 2x16 bit).

@shred Excellent! I'm hoping to get my STe functioning properly this weekend. It's already running TOS 1.62 so I think I'll just leave it there for now.

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@shred Possible casualty from the 'five inch drop fix' - ie: 'raise the case five inches and drop it to reseat the chips'

@shred I used 27C256, but also some electronically flashable ones: Atmel AT29C256 90PI 28 DIP. They worked pretty well and you don't need UV for deleting, just the prommer.

@shred Never mind. Thorsten Otto made some kind of release from the NVDI part of the open sourced MagicMac, if I remember it correctly. This is so fast, that a blitter is not so important anymore. At least not, if you have a cpu running at a higher frequency or 68030 or such.

@shred wait i'm confused. you have a working two-chip TOS?

why mess with it?

the board is designed to take either six 256kbit ROMS or two 1Mbit ones

and not at the same time

the board is set for two chips. that's why there's only two sockets. you will have to change some solder switches to do six chips

@shred ah i see, atari used nonstandard 28 pin 1M roms. so if you really want to homebrew upgrade it i suppose moving to six chip is easier 🙃

still, be aware TOS 1.0 is fine if you're just going to run floppies/emulated floppy

1.4 is mainly useful if you use a hard drive a lot, and even then with the proper patches loaded i ran a hard drive on TOS 1.0 for years just fine

@Seg Thank you! I still know too little about the ST. But the upgrade to TOS 1.4 is rather an "I do it just because I can do it" thing. 😉 I enjoy fiddling with hardware.

@shred The great part I always found with ST's is you can use (if you have 'em) normal PC floppy disks.

An emulator would still be great tho.

@shred 1.04 would probably be the best fit. From what I remember, 1.06 had mostly changed for the STE hardware.

@shred I installed EmuTOS on my 260ST. It has a harddisk driver included und is also able to make use of AlTRAM, if available. Also it is faster in some regards.

@shred Duh. For some reason I thought ... oh well. Probably been looking at the TT too much 🙄

@galaxis It's allright. I'm glad it's like that. If there were -12V, I would have had to refurbish the original PSU, or put a DC/DC converter somewhere.

@shred Friend of mine had one of these - played SunDog on it for hours.

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