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I believe that first one is an epson qx16 z80 / 8088 machine

This is probably a dumb question but so long as you use a 720k disc, doesn't a 1.44M floppy drive and HD controller adapt to that floppy?

I liked this software... https://www.oshonsoft.com/z80.php

Guess what.. they got 100$ more or less again.

Tr3 drives the gate of the switching fet. Is the signal SW-DRIVE also flatline? For this psu to come on you need 5V at the controller. Check that IC2 is regulating 5V.

Looks pretty dirty. I would probably try to brush off all that loose dirt, and then reseat every socketed chip. Especially the hard one to-do.. the square one called the GIME chip.

Hard to see the board damage unless you lift a Cap to see under. I would recommend that you try to recap and as you do that, visually inspect. Goodluck, very tricky to follow the way that JRC psu works.

I'm not selling this; just want to raise awareness of the auction. This one will be interesting to watch, because this seller previously auctioned this exact machine. It sold for about 100$, and the seller appears to have cancelled that sale and immediately relisted...

I did replace most or all of the eletrolytic caps. I found spares that I could make work. I did not order any new parts this time. Kind of a hack job. Do you have the schematic? It is posted at minuszerodegrees.

I personally used a 12V supply from my junk pile. It was a toshiba laptop supply. The trick was getting a barrel to fit, and polarity check of course. There is an ebay auction right now that has a z171 qith a small wall wart. Maybe you can see a part number in the image.

Appreciate the sentiments. I actually enjoy building, I just need to find time. Easier when the weather turns for sure. First snow today.

Regarding REX#, I built 25 units today for M100/T200. That's part of my backlog anyways.

I recently repaired a T1000xe to a working state. I used information I found online regarding T1600 if i recall correctly. It was very involved. I had to replace caps and some semiconductors...both ics and psu parts. I think these machines share architecture for the most part. There is a...

I would find any scrap crystal that is similar clock and just see if using that would allow a clock to be generated. That would rule out the crystal and maybe point to the controller.

No, little board changes that are fixes to problems get added in the factory after the pcb is built....those are barnacles. For your hardware to require reversed bits for video means you machine has inverted video as a default relative to mine. Very odd. But whatever works.. not the reason...

You must have a different hardware barnacle on there!

Here is a picture of 1 second during boot up. A13 seems to have a periodic nature to it that fits.

sounds like you have a good ram board now. you could try pulling the CMOS RAM (to reset contents). I guess the CMOS RAM is one are of potential problem. what if you have a missing address line at the cmos ram? Also, I would bet that even with a bad A13, you would pass ram testing. But you need...

I used 27C256. (in fact on all the eproms)

If you pull the memory card altogether and try to boot up, you should get an error at 0000 message. Try that, to see if at least that part of boot up is the same as others.