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I've been in touch with a guy who has an archive of reverse-engineered schematics, including for Mac IIsi and its PSU. I've told him I'm a restorer and he is willing to provide, but only by paper post and to a postal address in USA. If any other IIsi owner wants these and has a US address...

I'll have a look at DAVE too, thanks. My setup has a mixture of Linux, Win, MacOS and OS X machines in a flat network with no central file server, so SMB is really the best option. Rick

Looks like you scored a bunch of handy little project boxes with them as well. Then you screwed him for a discount }:) . Hope he is still a nice guy.

Looking to source suitable heatsinks, I found these ones with their own thermal adhesive tape. Tape shouldn't be hard to remove, if required, with normal cleaning solvent. For $2 including postage, hard to go wrong! Since my IIsi has been running for >20years without them, it can wait a...

Thanks - good info

Yay! My guess was close. Keep another one with the LED so that if it REALLY floods you can signal a passing helicopter for rescue :beige: Rick

Running some tests over a few hours with the IIsi case open, I found that the CPU and the two LSI system chips seemed to get steadily warmer, quite hot to touch after about 4 hours. In principle. cooler chips should give better performance and live longer. I'm thinking about sticking some...

This is a good reference - thanks for the thread link. I would add that there are four screws fixing the logic board to the baseplate. Three metal screws near the perimeter, and another NYLON screw nearer the centre. This functions to ensure good contact between those ICs under the logic board...

On another forum I've been asked whether a 3.5" 1.4mb superdrive (as standard in SE-Mac II) can be connected to a Plus logic board. My assumption is that the earlier ROMs will not recognise a Superdrive, even as a 800k drive. Mac docs do not suggest it is possible. Has anybody tried this? Rick

Your latest post reinforces the earlier advice to start replacing capacitors. If that does not solve all problems, it will at least eliminate many possible causes and help you to isolate remaining problems. Rick

Well yes, octet is more logical. But since France is the home of the universal decimal system, I would like l'Academie Francaise to insist that a 10-bit dataword is the norm, so the common byte should be a ".8" ;)

Good score... Does shorting those brass tags also turn on the LED? The IC looks like it could be a 555 timer or similar? Some sort of alarm signal with flash or timed on or off delay? The circuit shouldn't be too hard to figure out by looking at the IC datasheet and following the connections.

What kind of bad pic? The G4 lamps are old enough now to be developing problems inside their LCD monitors. You can find threads about troubleshooting the monitors and there are some caps or controller boards that can be replaced. But first, try an external monitor (via mini-VGA port) to see...

Yes - it is a perception thing. I don't have software to do meaningful tests on the 512ke, which is a single-floppy setup. I suppose I could more easily test the EPROMs on my Plus logic board with SCSI HDDs and ZIP. Maybe it's just a momentary joy that will fade with the next problem :-/ Rick

Just to round this off - I finally got some 27C512 EPROMs through the mail. It only took a few seconds to copy the Plus ROMs, burn and verify. They are 100ns EPROMS and seem to boot the 512k logic board even a little faster than the original Plus ROMs. And I have backup files, which is a nice...

Thanks guys - this is the information I was looking for. Does this summarize it ? The magnetic coating on a 3.5" HD floppy is calibrated to record with a higher charging current than the coating on DD floppies. A drive that detects a DD disk will only write at the lower current standard for DD...

When I think about it, a drive that can write 1.4mb is probably writing more tracks per side than a drive that writes 720-800k. I know that is the case with using a DVD writer to make a CD - it simply writes fewer tracks and leaves bigger gaps between tracks, which is why some older CD players...

Yes, there is even an Apple Support article that says that. Does anybody know WHY that would happen? Do the re-formatted tracks somehow save a lower density signal? Normally, whatever is written to a magnetic medium (format or data) remains pretty stable. Even if some of the previous...

This topic is probably an old chestnut buried somewhere, but I couldn't find a thread about it on this forum. :I I need to make a number of 800k disks from images for my 512ke, but I don't have any 800k-specified disks. I can use the superdrive and software in my IIsi, or the 800k drive in a...

Great! Hope they lay silicon eggs for you :p