Very old STM restoration project

[Steve]

Hi guys,

I have come across plenty of yellow Ataris in my time but this one takes the cake. It seems to be a very old model and even has that illusive japanese made mechanical keyboard that people talk about (first time I've come across one) The motherboard has quite a few bodge wires from the factory - but from what I can tell, I'm the first to open this baby up. Luckily - condition wise, besides the yellow, is excellent - absolutely no sign of corrosion or moisture, no rust what so ever. Even the metal shielding is untarnished.

I'm going to be restoring this baby and then sending her back into the wild.
Serial number is: A163D4000852
Motherboard rev: C070243 Rev C

Oh and luckily comes with its original box with matching serial number, how lovely

Here are photos from my google drive:
https://drive.google.com/drive/folders/ ... sp=sharing

[DoG]

Was the sticker still on it from factory? Underneath on of the screws? The solder fix doesn't look like factory mods to me.


EDIT: Looks like the modulator was added later. Maybe it was factory, but all the black residue from the flux looks strange.

[Steve]

Was the sticker still on it from factory? Underneath on of the screws? The solder fix doesn't look like factory mods to me.


EDIT: Looks like the modulator was added later. Maybe it was factory, but all the black residue from the flux looks strange.

Good spot! I was wondering why this was classed as an STM but the badge just says ST. The information on the box and stickers say STM so it must have been modified in the factory I guess... It didn't have a sticker covering any screw holes though. Perhaps this explains the change in serial number as well? Maybe they took ST models and retrofitted a modulator to become STM and then changed the serial number in the process.

[stephen_usher]

The STM has only "ST" on the badge.

I must admit that was quite suntanned, though the plastic on the STM does seem to be more sensitive as mine went quite orange and it never had direct sunlight. (It was in a room for a long time with a north facing window.)

In the end I had to spray the upper case of mine as the plastic didn't respond well to retrobrightening. Also be careful of the badge. The paint on the original badge seems very sensitive to isopropyl alcohol. On mine it caused the paint to just lift off so I had to use an STFM badge and paint over the "FM" to hide them as there are no replacements available, anywhere! (Best Electronics doesn't have any for a start.)

Just to show you what's possible, here are my before and after pictures...

IMG_1570.jpg (61.56 KiB) Viewed 4460 times

IMG_1618.jpg (74.84 KiB) Viewed 4460 times

Anyway, it sounds like a fun project, and I like the unusual keyboard!

[Steve]

I would be inclined to remove the modulator completely, as I have done previously on my falcon. But I noticed on other ST mobo photos they seem to have some resistors&transistor 'terminating' the input/output parts of the missing modulator. Could anyone let me know if I'd need to add these if I remove the modulator?

[stephen_usher]

I've not seen this on any other types of machine, such as Amiga A1200, as the modulator is just taking the composite input, as a monitor would.

[czietz]

I would be inclined to remove the modulator completely, as I have done previously on my falcon. But I noticed on other ST mobo photos they seem to have some resistors&transistor 'terminating' the input/output parts of the missing modulator. Could anyone let me know if I'd need to add these if I remove the modulator?

If you're referring to this: https://www.exxosforum.co.uk/forum/downl ... hp?id=4097, that's to create a composite sync signal in the absence of a modulator. Important if you're using an RGB-SCART cable. In later revisions this circuit was included on the board (for STs without modulator).

[Steve]

Yeah that's what I mean. Cheers for the info.

[Maximilian]

Nice project,

Make sure the glue holding the wires on the underside of the board hasn't gone bad and got conductive, please test before powering on.

[Steve]

Nice project,

Make sure the glue holding the wires on the underside of the board hasn't gone bad and got conductive, please test before powering on.

Cheers for the tip, never heard of this, good to know!