I have dumped the 2 EPROMs, I'm attaching them to this post. The first chip is marked 250235-02 and it's located in the second EPROM socket from the edge; the second is 250236-02 and it's in the 4th socked from the board's edge.

And FWIW the 2 files merged bitwise.

I opened the box bolted to the side of the PS. There is no electrical connection between the PS and the box, it's completely separate. I'm glad nobody took the bet on the battery inside, because there isn't any. Here's what is in it:

An oscillator and associated circuitry. There's also a jumper block, with 2 jumpers labeled "60" which are closed. Three of the other jumpers are labeled "48" and one is unlabeled, all these are open. So it's an oscillator, but why in a separate box and not integrated in the motherboard? Who knows.

I also mapped the power supply connector. Here's a drawing with associated voltages. These were measured with no load. There's GND, 5V, -5V, -12V. Not sure if the 9.81V is supposed to be 9V or 10V. There is no +12V.

The PS fan is noisy and will need to be replaced.

(edit) on second thought, the yellow 9.81V may be supposed to be +12V and it's out of spec?

It's alive! The ATI banner is from a random VGA card I found laying around and dropped in the motherboard for the first test.

Okay I hit a wall.

The system boots with only a VGA card in. I tried several VGA cards and they all work, though some seem picky about which slot they're inserted in.

But as soon as I add a second ISA card, it doesn't POST anymore. I tried several combinations of different VGA and IO cards, changed slots etc. Bottom line is: it boots with one card in, it doesn't with 2 cards.

I suspect the PS may be flaky. I measured the voltages in different combinations, and the picture isn't convincing.

First off, the yellow is indeed +12V. Even though it reads below 10V without a load, when connected to the motherboard and with one VGA card in (configuration that boots) the yellow reads 12.48V. Wit a second ISA card plugged, it reads 12.00V. A significant drop, sure, but still perfectly within specs.

The 5V line (red) reads 4.90V when one card is inserted (and boots) and 4.96V with 2 cards (and doesn't boot).

The -5V and -12V don't change significantly with 1 or 2 cards plugged, still read very close to the picture above.
The white line reads 5.00V also not changing with the number of cards.

So overall it doesn't make much sense. Yes there is a drop on the 12V line, but I think not significant enough to stop it from booting. And the 5V line voltage actually goes up and closer to 5V with 2 cards.

CAn anyone think of an explanation?

Ancillary question: can you identify the type of connector that the power supply uses? If I could find another one like it I could make an adapter to try and use a regular AT power supply instead. The only marking on the connector is "J H P22" printed on one side.

Congratulations, nice board! However, as you can see, there seems to be nothing Wyse-specific in it - except the non-standard connectors. Also the BIOS is a standard Phoenix one, not even the brand is displayed.
You will not need any specific Software for it.

Hope you will also get some EMS cards running in it 😉

Predator99 wrote:

Congratulations, nice board! However, as you can see, there seems to be nothing Wyse-specific in it - except the non-standard connectors. Also the BIOS is a standard Phoenix one, not even the brand is displayed.
You will not need any specific Software for it.

Hope you will also get some EMS cards running in it 😉

Well for now as seen in my post above yours, I'd be happy if I could at least attach a FDD to it. 🙁
Eventually I want to have in it either a Rampage 286, or a lo-tech 2MB card (and probably a 1MB card also so I can have some UMBs).

Check the solder joints for cracks or cold spots, check and repair the traces, and spray some contact cleaner in the ISA 8-bit and 16-bit slots. Could also be a bad or failing capacitor as well.

I've inspected the board closely, it is very clean and all solder joints look good. There is no corrosion and no tracks to repair. There is a grand total of 4 aluminum capacitors on the board, all look good. This board was made way before problematic capacitors appeared. Yes good capacitors can go bad but these don't look like they have. Some of the others may be tantalum, but in my experience those don't cause problems if they don't explode, and none did. I cleaned the slots with an electronics cleaning spray then inserting/removing cards from them a few times. It did not make a difference.

How do you know the board POSTs only with the I/O card installed when you dont have a VGA in at the same time?

Did you try other cards together with VGA (Sound, SCSI, ...)?

Predator99 wrote:

How do you know the board POSTs only with the I/O card installed when you dont have a VGA in at the same time?

Did you try other cards together with VGA (Sound, SCSI, ...)?

The VGA is in at all times. It posts with only the VGA. If I add another card, it doesn't POST anymore. I haven't tried anything else but I/O cards yet. Can't get anywhere until I can attach at least a floppy drive.

FWIW here's a link to the setup disk, DOS 3.1 and DOS 3.3 that I got from someone on reddit. They are in ImageDisk format, easy to convert to more common .img or .dsk but if anyone wants them I can upload the converted images too. The ones I converted to .img work fine if placed on a USB drive and into a Gotek emulator flashed with FlashFloppy (tried them in another computer).
https://archive.org/details/Wyse286

stamasd wrote:

Predator99 wrote:

How do you know the board POSTs only with the I/O card installed when you dont have a VGA in at the same time?

Did you try other cards together with VGA (Sound, SCSI, ...)?

The VGA is in at all times. It posts with only the VGA. If I add another card, it doesn't POST anymore. I haven't tried anything else but I/O cards yet. Can't get anywhere until I can attach at least a floppy drive.

Then try some other cards to know if there is an issue with the the power supply etc. I guess its just an incompatability. I have several of these I/O cards that dont like to run in a specific board. Did you already connect cables to the I/O-card? Remove them and try without.

I've tested about 12 VGA cards and 8 I/O cards in various combinations with the same results. After the initial 1 or 2 tests I've disconnected the floppy cable and the power cable from the FDD emulator. No change.

I think the power supply is at fault. I don't like the wide variations of voltage on the 12V line. I have found info on the power connector (see the similar thread I made on vcfed) and have ordered what I need to make an adapter cable for an ATX 1.0 supply. Hopefully will work better with that.

Hmm, dont agree to that conclusion yet. Insert some Soundcards just to be sure...they also consume power even if no driver is installed.

Hmm... good if puzzling news.
I started retesting the system today, using the same cards as yesterday. Surprisingly, several of the VGA+I/O combinations which would not allow the system to boot yesterday, do boot today. I finally settled on using a OTI077 VGA + UMC I/O for further testing. I did not do anything else to the system, just let it rest overnight. I didn't have time to check the voltages again.
Now to find my lo-tech ROM card with XT-IDE so I can start working on attaching a CF or microdrive to it.

That's promising. Good luck.

More info after some brief experiments yesterday (not much time to do things, and today will be the same).

1. It does not remember its settings. If I power it off for more than 5 minutes, when it's turned back on I have to run setup again because all the info previously set is scrambled to random values. The type and number of FDDs is scrambled, same with the HDDs, memory, boot speed etc. The board as you noted has no battery; I was suspecting that the little box has a battery but that's not the case. There may yet be a battery inside the power supply but I haven't opened that up to check. But after 30+ years that is probably dead.

2. Still having boot problems with various card combinations. After I somehow made it boot with a VGA and an I/O card in, I wanted to add a lo-tech ISA ROM card with the XTIDE firmware. That is still a WIP because I can't get it to both boot and recognize the XTIDE. Depending on the address, either it boots but the XTIDE doesn't get activated, or it doesn't boot. At least the results are somewhat consistent: address 0xC0000 or 0xF0000 it boots but without XTIDE, 0xC8000/0xD0000/0xD8000 doesn't boot.

I'll see what work I have time to do on this during the week-end.

Not much happening. Manual received from the benefactor on reddit:
https://archive.org/details/WYSE286pcManual/page/n0