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Testing/Repairing ST's

Nicolas 2000

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Apr 23, 2022
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Belgium
I have, untested and no known history:
-a 1040STFM
-a1040STF
-520ST

I have no power supply for the 520, and no monitor cable. So I wanted to start with the FM so I could use its video output. I thought this was a composite out, but I think it's RF? That would explain why I don't get video on the composite input of the monitor... I can solve that by moving to the living room and hooking it up to the TV. But before I do that, first some questions for you. This STFM seems to be rather modded.

Overview:
1.jpg

Is this a 4MB RAM expansion?
2.jpg

Is it normal to have these 6 EEPROMS(?) and what do they do? Is it a dual TOS mod, if so how do you use that? I don't see a hardware switch.
3.jpg

It seems like there was a mod at the RF section, tapping from the monitor out. Any idea, composite out? In that case it doesn't work. :)
4.jpg

I know it's Atari lore to recap and that often it's not really required. I think I'll replace this one though...
5.jpg

The supply voltages are good. The ST switches on, and with the TOS disk (unless it's overwritten as it has names of office software on it...) I hear it searching/loading for a few seconds after booting. But without monitor output, it's hard to say whether it really works. I've never used an Atari before. Will it boot without any disk inside? If I try that, I hear a short activity in the disk drive every few seconds.
6.jpg
 
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Gary C

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No, it needs the disk to start the operating system, the fact that it keeps trying the disk when its not there is a good sign its mostly working.

But without a display, its not really worth thinking about it anymore as its all guesswork.
 

Nicolas 2000

Experienced Member
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OK so it might be worth to spend on a SCART cable upfront, as it is giving good signs of functioning.
 

Nicolas 2000

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I would if I had the connector for the Atari side somewhere in my inventory. (I don't feel like ramming individual pins into the ST...yet) If I'm going to buy that connector, I might as well buy the whole cable. A shop near me has an ST RGB SCART cable for a good price.

However, I see now that I'd need just two connections to get a composite signal out of the ST (pin 2 and 13) so I might just do that.
 
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Nicolas 2000

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I couldn't help myself. When I saw that the composite signal was readily available in the plug... DWI it is! Your colleague can be proud:
11.jpg

And what do we see now:
13.jpg

The colours in the Atari logo are also nicely animated. However, this particular disk -the only one I own- also has another program, a splash screen of sorts, and it looks weird:
12.jpg

Problem with the Atari, with the disk, or is this some sort of stereoscopic image that requires other magic to look alright? I could really use some other software to test things. I'll see if there's a way to use a regular PC with a disk drive and 2HD disks to create some disks from ST files that I ...found...
 

Nicolas 2000

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Apr 23, 2022
Messages
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Location
Belgium
The good news about this composite hack is that I can now also test my other Atari's. Well, the 520 will be a challenge as it will need a power supply hack and I also don't have a disk drive for it...that one might just go on the market as "untested" after I've taken a look inside. But at least testing the 1040STF should be straightforward once I can get some decent software for the STFM. I'll look into that in the coming days. I've got an XP PC with a diskette drive somewhere, hopefully I can use that one to create Atari disks.
 

Nicolas 2000

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My reasoning is, if that screen is so messed up because of hardware faults in the Atari, the other screenshot wouldn't be perfect either. But I'd like to see it perform software with some graphics complexity first to confirm the Atari is healthy.
 

g4ugm

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No, it needs the disk to start the operating system, the fact that it keeps trying the disk when its not there is a good sign its mostly working.

But without a display, its not really worth thinking about it anymore as its all guesswork.

An ST with six ROMs does not need a floppy to boot. It will try and read it several times before it gives up and loads the desktop.

The split display could be the program sets the ST in Hi-Res mode or it could be a 3-d image for use with LCD shutter lens that ATARI made.

Many STs had single sided floppy disks which can be a challenge to create on a PC.
 
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Nicolas 2000

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Maybe I wasn't patient enough, but all I got when booting without disk was a blank white screen and multiple attempts to read a disk. I'll try again tonight. Maybe reseat the roms.
 

vwestlife

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No, it needs the disk to start the operating system, the fact that it keeps trying the disk when its not there is a good sign its mostly working.
Except for the very first ST's which did not have TOS in ROM, you do not need a boot disk, however it's a good idea to put any kind of disk in the drive, even a blank one, otherwise it'll wait a long time checking for the disk before it times out and finishes loading TOS from ROM.

And any ST with a built-in RF modulator has composite video on pin 2 of the video output port:

1853691487_AtariMonitorpinout.gif.8a0a89e80436e50a63bacc0450ca0df5.gif
 

Nicolas 2000

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Belgium
With a bit more patience, it did indeed boot to TOS without disk. Not that I can do a lot in TOS without a disk. At least, not that I found. I'm not familiar with ST's and it's a German TOS.

I assume the weird split image in my previous post has to do with 3D glasses (the disk mentions a program called 3Dgrafik or something like that) and the Atari itself is healthy. Nice! So, tonight will be all about trying to get some software on a disk for it to run.

And cleaning the left mouse button to make it more responsive, as this will not go down well in games...But I'm not sure how to approach it without replacing parts as it appears to use closed microswitches.
 
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Nicolas 2000

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After some magic with my old Pentium 4, I've been able to make some ST discs. The STFM plays Advanced Ski Simulator (horrible game, or is that just me) and Prince Of Persia just fine. I've expanded the dangly wires to include audio. It picks up quite some hum due to its beautiful esthetics, but apart from that it does demonstrate that sound works. So I assume this Atari is in proper working order.

In the coming days I'll test the 1040STF and see if I can find a way to test the 520ST (no supply, no disk drive). After that, I'll have to decide which ST I'll keep, if any. Because there's also an Amiga waiting in line, and game wise the Amiga appears to have huge overlap with the ST.
 

Gary C

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There was a lot of overlap in the A500/ST era as both used the same processor and games could be fairly easily written to run on both with minor recompilation.

Used to irk Amiga owners because that meant some games really didn't use the more advanced blitter graphics etc.
 

Nicolas 2000

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Apr 23, 2022
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I had some time and energy left, so I had a look at the STF. I've opened it up first. It looks original. Still has all the metal covers and after some disassembly I couldn't see extra's when peeking underneath it. It also doesn't have six ROMs. So this one looks bone stock on first sight.

I measured the PSU. 5V is spot on. 12V (unloaded) seemed a bit low. Can't remember exactly, but I think more like 11V.

Reconnected everything and tested with Prince Of Persia. Everything seems to work fine, loads the disks, game runs, sound ok.

But...NO IMAGE. Just a black screen from start to finish. When I switch the STF on I get a white flash for a fraction of a second and then only black. Disconnecting GND or pin 2 has an effect, so they're making contact. But no image. Could this be because of the low 12V or any other suggestions on where to start looking?
 

Nicolas 2000

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Apr 23, 2022
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Belgium
I found this quote on another board:

Ok, after some exhaustive googling, it turns out my STf is *probably* working fine. The cable I purchased on ebay has a composite and left/right audio out in the form of RCA connectors, however, I found a page that explains that ST's without an RF modulator, do not output composite video on pin 2. Basically, I need to buy a RGB cable to connect this to my Commodore 2002.
If that's the case, no pin2 composite video on the STF model... That would explain a lot. 🙃 So the good news would be that it might not be broken at all. The bad news would be that I'd need to arrange an RGB SCART cable to test it (my old Philips CRT monitor has a SCART input). I hope this STF at least does have composite sync on pin 2, as some people mention most but not all STF's do.

There might be some resistor magic involved with getting it to work (been there with the Sega's...) but I should get image with the RGB SCART cable.
 
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g4ugm

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If that's the case, no pin2 composite video on the STF model... That would explain a lot. 🙃 So the good news would be that it might not be broken at all. The bad news would be that I'd need to arrange an RGB SCART cable to test it (my old Philips CRT monitor has a SCART input). I hope this STF at least does have composite sync on pin 2, as some people mention most but not all STF's do
If it does not have a modulator there is sometimes no composite sync on pin-2. If you buy an Atari SCART lead it usually has diodes and resistors to fix this.

ST=> Original Model, No Floppy, No Modulator, may have no TOS so needs a TOS disk
STF => F for floppy. So has PSU, TOS and Floppy - Often single sided.
STFM => F for Floppy, M for Modulator, has composite. Floppy may be single or double sided.
STE => Enhanced. Has floppy, modulator, and SIMM memory (may be SIP for easy expansion to 4Mb.

it does take ages to boot to the desktop, you can then add pop a disk in the drive and explore it. You should also be able to switch between low and medium resolution.
 

Nicolas 2000

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Apr 23, 2022
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Location
Belgium
If I peek through the slots of the metal shield of my STF, I can just make out 3 resistors, 2 diodes and 1 transistor in the "RF200" designed area where the RF modulator would sit in the FM model. So I'm quite sure my STF has the composite sync circuitry.

In which case I hope that the RGB SCART cable I'm about to buy doesn't have those components as well or wouldn't that clash...
 
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