Reply 80 of 174, by MMaximus
I asked about ATX power supply beacuse pretty much all decent ones are 450W+ so the effect with the LED is easy to spot. But you […]
I asked about ATX power supply beacuse pretty much all decent ones are 450W+ so the effect with the LED is easy to spot. But you can try that with AT PSU as well, though the results might not be conclusive. The reset switch works as it should on your mobo and so the problem doesn't seem to be reset related.
BTW the JP2 and cable for the test card are to connect the buzzer on it in place of PC speaker. You can verify that by testing connection between those two on the card. No idea what the button is for, I've never used it.
Well it could be the BIOS got corrupted. Not by UV light, unless you kept the board out in the direct sun without the EPROM windows covered. Fluorescent light doesn't really erase these unless it's years of exposure. Or lamps used to kill germs. EPROMs sometimes just flip back to "1" - it's a natural process that takes years even for weak cells but it happens. The mobo should output some error codes even without RAM, so long the CPU works and the chipset is not completly dead.
Do you have something to dump the EPROMs? Or maybe another board to try swapping both?
This mobo uses Motorola RTC, MC14618A - a very common chip. I'm actually surprised there were any Suntac 286 with Dallas chips. Must've been pretty late models.
Thanks for all this useful info. I swapped the EPROMs with ones from a working board and the board still doesn't work - whereas the working board works with the EPROMs from the defective board so we can probably rule this out. I'm waiting for a cheap PLCC extractor I've ordered to arrive and then I'll swap CPUs and see if it's the problem.
Hey I think I have this exact same board in my 286 !
What's odd though is that I can't see any RTC on your board ...
Mine uses a DALLAS rtc chip, but I don't see it on yours either it's actually not the same board, or they used a different way, or it's missing on yours (I haven't opened my 286 since some time now so I don't exactly know where it is, I'll try to check that a bit later)
They look very similar but my boards had barrel batteries that I've removed. I'm now using external battery packs, it works really well.
I had 5 identical boards in total: I put one in a system that I sold, gave one of the non-working ones to Predator99, and now I have 2 functional boards and 1 defective left. I'll see what I can do with the non-working one but if I can't repair it I'll gladly give it away to someone who would want to have a go at it. 😎
Yes, jumper is for speaker connection. Button is for switching back to the previous code displayed.
Thanks for the info!
Yes, can you dump your BIOS please? You can do that with NSSI without removing chips. Does it run with 16 MHz..?
I'd be interested to see if the BIOS from Deksor's board is a different one: the one on mine and Predator's is Phoenix 3.10.22. Deksor, does your BIOS offer you the option of user-type HDD?
Actually I was thinking the same thing about 16Mhz... would our boards work at 16Mhz if we swapped the CPU and the crystal? Predator let me know if you try this 😀
No the CPU is 12MHz on mine. Actually I wish I had ram chips to upgrade to 4MB, but I'm stuck to 1MB unless I pay 60€ of ram chips.
I didn't know 411000s were so expensive! 😲 All the boards I had came each with one bank of 411000s to give 2M RAM, so with both banks full it gives a total of 4M.