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Have to agree with wmcbrine above, you can't beat just putting a 62256 RAM in in place of the original 1K or 2K RAM and soldering a few extra wires to link up the higher address pins. The end result is compact, stable, and uses less power, you can even do it to a ZX81 in its original case so it...

Another thing about finding them in their original packing - it's not just the case that they are much more likely to survive in onward transit, they are more likely to have survived in storage as well. I have seen quite a few PET resurrection cases where the machines clearly must have been kept...

As per above, I would always prefer to receive anything, not just old computers, in the exact packaging the manufacturer shipped it in because it was specifically designed to protect it while in transit - for the same reason, I rarely discard the packaging or foam inserts which items I buy come...

Fair enough, carry on...

If you recall, TOS 1.0 has problems with DOS formatted drives of which your Hard drive SD device may be an example. A better test might be to try the same thing with your TOS1.04 EPROMs in it.

The problem here is going to be catching it in the act - you'll need to make some measurements when the fault is present, although you seem saying that it is reliably unreliable when first powered on - if so that will be quite helpful. Genuinely intermittent faults are an absolute nightmare to...

The 520STFM I have here is my original one from about 1986 and it did originally have both TOS 1.0 and a single sided drive. I soon fitted TOS 1.04 in 6 EPROMs and a DS drive internally but the specific ones with the Atari ST form factor (wide, rhombic eject button) were not widely available...

Yes and no. The original single sided ST floppies are 360K and are not actually an entirely DOS compatible format so old commercial software sold on floppies formatted in the original proprietary ST format was and still is not readable or writeable with a contemporary DOS machine - not without...

r_s is plugging that same connector into a modern PET PCB substitute and it appears to work, although you can certainly see that the socket receptacle in the J8 / pin 4 connector in your picture had been running hot for a long time at some point. That one is a very good past example of the...

That is a reasonable assumption but you could still have a problem on the male pin row power connector J8 on the PET mainboard. Just check that those pins are really clean and not tarnished, oxidised or burnt, before moving on.

Just before the experts get here, one very common cause of intermittent power / no power / power / no power problems on these is the plug / socket connection between the power supply block and the mainboard. The plug / socket in question usually has the designation 'J8' and it is one particular...

I've probably said it before but for me the deal breakers were non-linear mazes - those ones where moving east from A to B and then moving west from B didn't necessarily take you back to A. I found those exasperating, in fact, encountering a non-linear maze in a game was sometimes enough to stop...

I don't know the software but that would be such a fundamental requirement - to have not only the VIAs but all other through hole plated pads exactly matched up on both sides - that I am sure the software will have a way of handling it. I think if I was trying to do this I would start by either...

I understand that the latest / current version of the PCB design software KICAD has a mode where you can import a photo or scan of an original (unpopulated) PCB and then place another drawing 'layer' on top onto which you can effectively 'trace' the tracks of the original PCB, one-for-one, in...

It would be better to try narrowing the fault area down through logical fault tracing rather than by playing 'parts darts'. Here is the service manual for the SF-354. http://info-coach.fr/atari/hardware/_fd-hard/ST_SF354_ServiceManual_v2.pdf Service manual for the SF-314...

Well done Dabones, I thought for sure it had to be something to do with the ROM images because I knew for certain that my ST has its TOS 1.04 in 6 x 27C256. Unfortunately it wouldn't have helped Verault much to give him images of those EPROMs because mine is a UK model of course. Regarding the...

Could you show where you got the ROM images from, and how they are identified (in other words, how does the information which accompanies the ROM files indicate which chip should go into which position in the ST mainboard)?

Interesting topic. I think it depends on the system, its rarity, and the mood I'm in at the time. My Atari STs have more memory than they were made with, one has a contemporary memory expansion fitted to take its original 512K of memory up to 2.5MB. As this was my main, all purpose computer at...

When you say you viewed it do you mean you viewed it working? If not, do you have the patience, tools and skills to carry out any necessary repairs yourself?

Just looked that up, and although it is a discontinued product, I saw the price it once sold for, Woo! around 500 to 600 dollars. Just wondering if your ST is actually a USA model - it seems likely, but then I think you imported your Spectrum from the Mediterranean area somewhere, so it's not a...