Add some RAM 😉 Check the labels near the sockets, bank 0 should be populated as a minimum.

Nice board. Hope you get it up!

It has 512KB in bank 0 😀 . The board came with all the banks filled (yeah, that's a lot of chips) but behaved exactly as described, so I've removed them all and only populated bank 0 with known working ones. Without RAM the board stops at code 10 and gives the endless three beeps series.

OK 😉

1A is:
AMI (1A)Memory refresh line is toggling. Going to check 15 micro second ON/OFF time. Return from optional video ROM. Optional video ROM control OK

How does it behave with/without VGA card? Also tried a CGA? In different slots?

I have tested with various graphics cards (almost all ISA cards that I have). With a video card installed, the motherboard stops one step earlier (code 19 instead of 1A), and the monitor gets initialized (LED turns blue, but nothing is displayed).
Also tested with my single EGA card, and since I don't have any EGA monitor all I can say is that it stops at code 19 with this one too.
No CGA card unfortunately.

Usually there is jumper to switch between color and mono. Maybe its set to mono? Try to switch all jumper you can find.
I think there are good chances your current config runs with CGA. EGA is basically the same as VGA. Both have their own BIOS which doesnt seem to initialize correctly. However, the switching of your monitor LED indicates something is going on there...
Can you also try without keyboard-controller? Just to see if something changes...there seems also to be some corrosion damage in that area - did you try to check the traces?
What beep-codes do you get?

Thanks for your input. Well... I've tried to keep the story short, thus omitting some details that I thought wouldn't make any difference.
The board had some battery corrosion, and after removing the components in the affected area I found two broken traces. Repaired them and many others that had even a tiny bit of corrosion. Also found many of the switches didn't make proper contact. Dismantled the DIP block, it was full of green gunk. As I didn't have another on hand I restored it to factory condition. Vinegar, WD40 and a lot of work with tiny pieces 😀
After repairing the two broken traces I was very optimistic about the board, but after soldering back the components it was stuck as before, code 16. No change at all.

That's when I started tinkering with the switches, and found out a combination that allows the board to progress to code 1A. I also changed, one by one, all the jumpers on the board, to no avail.

I've tested with other KBC chips and even without one - no change; found on the net (chukaev.ru54.com) a newer BIOS image for the exact same chipset, burned it into two 27C256 but nothing changed, so this rules out a possible corrupted BIOS.

Somehow I don't think it would work with a CGA, because I never encountered so far a board that wouldn't POST without a video card (with the proper beep code / error, of course). But of course with a CGA I could use the supersoft diagnostic ROMs...

The only beep codes I get are the endless series of three beeps when I'm testing without RAM. With RAM installed, no beep whatsoever.

Here are some more pics of the board, including the battery area before and after repair.

Another quirk of the board, it doesn't seem to have a Reset header, or it is not functioning properly. One of the 4-pin headers in the lower-left corner is for speaker connection, and there are two other 4-pin headers, I suppose the Reset should be among them. But I've shorted them in any combination and the board doesn't reset. I've checked all the logic chips with my TL866 and found no problem, so this might indicate a chipset problem I guess?

You should try the Supersoft, it outputs also on the speaker via beep code. You could also try Ruuds-ROM
http://www.vcfed.org/forum/showthread.php?682 … mpatibles/page9
I didnt follow it anymore, but I think he planned output on VGA and serial port.

Nice board and excellent restauration work!

Okay, so I built the simplest CGA/EGA adapter and found a video card that can display the Supersoft diagnostics on my monitor. Doesn't look too good, I think:

The position of the jumpers and switches doesn't seem to matter. Testing still in progress.

quicknick wrote:

Okay, so I built the simplest CGA/EGA adapter and found a video card that can display the Supersoft diagnostics on my monitor. Doesn't look too good, I think:

TACT_supersoft.jpg

The position of the jumpers and switches doesn't seem to matter. Testing still in progress.

Maybe your chipset needs some initialization from the BIOS and Supersoft shows nonsense?
What graphics card is this..? 😉

Could be, but it doesn't properly POST even with its own BIOS, so...
The card that worked best for me is the monster at the end of the first post, here.
Before that I tried my American Microland EGA card, it looked like this:

Strangely, Supersoft ROMs even worked with one of my VGA cards, (CL-GD5320 based), but with one third of the image missing, and not on every attempt:

No other VGA card initialized the monitor, and in all three cases the image is very small, I'd say about 10% of the screen size, and the monitor (EIZO FlexScan L985EX) is complaining about some out-of range frequencies (too high vertical for the VGA and too low horizontal for the EGA and whatever is the large Compaq card 😁 )

Interesting, also have to try this with my VGA..!

How does the original BIOS behave with your Compaq CGA?

With the original BIOS (and the updated one from the Russian site), when using the Compaq card it stops at code 17 with the same switch/jumper settings that go to 19 with a VGA card. The monitor gets initialized but nothing is displayed.

Sorry, no further idea. Maybe you can read some other 286 repair threads to find a point to continue...
Re: Suntac 80286 Mainboards
[SUCCESS!] Old KEnitec 286 Plus (suntac) Rescue, will need help.

35-2309-1 -> PcPartner/Vtech code indeed
702236 is another number they will use inside their documentation.
Alas, so far I cannot find info on 286 boards from them. If I find something I'll post it here.

Thanks. I've kind of put it on the back burner, but I'll revisit this board for sure. Nothing with TACT chipset will go into the bin!

The original BIOS probably initializes the TACT chipset, whereas the Supersoft doesn't. If the (8254) timer was not working you wouldn't get any beeps from the motherboard.
Error '16' to my knowledge is a failed CMOS battery, '19' failure to find the video BIOS, '1A' failure to return to the system BIOS from the video BIOS.
This would suggest the video BIOS is stuck in a loop.

Can you dump the original AMIBIOS rom?

Of course, here's the BIOS (original LO/HI images, and the two unified in one image via WinHex). The BIOS itself is working, PCem can boot with it.

Played a bit with the board about a month ago, without much progress, after stumbling across a similar one for sale, identified as Laser L286-3 CIJF. Mine has CIJC on a small sticker, so probably an earlier revision, as witnessed by the different bodge wires (mine doesn't have the resistor network on the back, but instead some bodge wires connecting to a F245 chip near the CPU).

I finally identified the reset header too, it's the two middle pins (2 and 3) of a 4-pin header, which is kind of strange.

One other thing noticed while checking for proper clock signals, the CLK that reaches the CPU is quite unstable, hovering about 28-30 but never quite reaching 32MHz unless I pop the CPU out of the socket. The crystal outputs a proper and stable 32MHz. The board is densely packed and full of sockets, making very hard to trace the paths, and so far I've been unable to trace the source of the CPU clock.

I have added it to UH19 here : http://www.win3x.org/uh19/motherboard/show/6236. If you figure out any infos about that board, let us know 😀