Hallo, I have got my hand on an pretty "modern" motherboard with a 386sx/40Mhz CPU. The board is pretty shiny, barell battery removed (leaked a bit but the corrosion is not sever - cleaned). The traces look good - some small vias look suspicios, but multimeter says continuity is there.
The board is not postig and giving 10 beeps repeatedly. (10c short beep-pause-and again). This should be "CMOS shutdown register read/write error. ".
However this DAT305 is a highly integrated board and I am afraid the chipset is faulty. I do not know which of these 2 chips contains the CMOS and can ยดt find datasheets. Especially the ALD chip is a black box to me.
I would apprciate any advise, help, links..This is a board of desire as I do not have many nice SX and not a single working 40Mhz. Thank you very much for any help!
Very likely an 82C206 (KS83C206 on that board) failure. ๐
CMOS shutdown register read/write error is a common indicator of 82C206 problems, as it integrates the CMOS memory, reset logic, ISA IRQ/ DMA and a bunch of other X-bus peripherals.
If reflowing the pins on the 82C206 doesn't help, it'll probably be high time to get the hot air rework station and a replacement chip ready, preferably a working one taken from an otherwise junk board. Getting a working 82C206 from eBay is a big-time crapshoot. (Most of the ones I was able to get from eBay, turned out to be faulty! >_>)
The KS83C206 is simply Samsung's take on the 82C206, it is fully pin and function compatible with HMC, CHIPS, OPTi, SiS and UMC 82C206 chips. I'd personally try for an HMC or SiS '206, I see fewer dead chips of those two makes for some reason.
Life isn't long enough to re-enable every hidden option in every BIOS on every board. ๐
Thank you very much for info on that chip and replacement options. Good to know. So one might sey that those ICs are common source of problems? I assume the CMOS part is sensitive.. ๐ I think I am capable replacing that chip. But finding the new one would be an issue. So you think even buying a "lot" of new ones on e-bay is risky? What is killing them - static electricity? Again, thank you!
When you tested the traces, did you check only the top layer or the vias as well? It's usually vias that corrosion destroys first, but the fix on these mobos is usually simple - gently expose the ends by removing solder mask with something like fibreglass pen, then put a short wire through and solder on both ends. The inner planes of the PCB are typically for power distribution and only the outside ones carry signals on these 386SX mobos.
When you tested the traces, did you check only the top layer or the vias as well? It's usually vias that corrosion destroys first, but the fix on these mobos is usually simple - gently expose the ends by removing solder mask with something like fibreglass pen, then put a short wire through and solder on both ends. The inner planes of the PCB are typically for power distribution and only the outside ones carry signals on these 386SX mobos.
Thank you. I am aware of this. But I will re-check the small vias from both sides. It is possible I missed something. However that board is not corroded too much - but yes, you never know. The battery looked quite Ok but still I found some green-blue residue. The wierd thing is the residue was only on several places - like one tantalum cap. but not so much arround the battery itself. I have a plan to check the bios integrity as well. Don ยดt know anything about the board history - bought for repair from a guy who lost the game as he is not in to board level repair.
If you have EPROM programmer and can read the BIOS chip, I might be able to tell you if the checksum is correct or not. As for '206 chips dying, I know people here reported such issues but I never had one of those going bad, most of the motherboards I fixed were down due to battery corrosion and deep scratches on the bottom that cut some traces (I usually pick out cheap mobos that already went through a garbage bin or two).
I assume you've tried different memory sticks? You need at least two in one bank, and some motherboards (though none as new as this one) don't like the 3-chip SIMMs. If you think you'll be fixing more of these or you really want this particular mobo running again, then consider buying a POST card. It really helps with issues like this one.
At least one of my 386SX boards (Opti 82c291 based) refuses to boot without all 4 simm slots populated. Can't remember what errors it throws, but it's not something memory-related, so this threw me off for quite a while when diagnosing it (dead KBC and heavy corrosion compounded the issues).
Thank you very much for info on that chip and replacement options. Good to know. So one might sey that those ICs are common source of problems? I assume the CMOS part is sensitive.. ๐ I think I am capable replacing that chip. But finding the new one would be an issue. So you think even buying a "lot" of new ones on e-bay is risky? What is killing them - static electricity? Again, thank you!
Unfortunately, I've been noticing quite a few 286/386/486 boards with dying 82C206 chips, so I'd personally say that they have a bit of a failure rate these days.
I don't know why they are starting to die off all of a sudden, I suspect the chips were perhaps a little too integrated for their time, and seriously pushed the limits of their process tech, but that's just my best vaguely educated guess. It's also possible that, since they are part of the ISA bus, they are vulnerable to spikes/surges/etc. and other potentially damaging transients that may afflict the ISA bus. Given that the power supplies (especially the more cheaply-made units) in many older computers are not necessarily aging with dignity, that would seem at least remotely plausible.
Life isn't long enough to re-enable every hidden option in every BIOS on every board. ๐
Hmmm no battery on the board, did you pull it ? and the Ext Bat pins are missing. just an observation.
Hate posting a reply and then have to edit it because it made no sense ๐ First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun
Hmmm no battery on the board, did you pull it ? and the Ext Bat pins are missing. just an observation.
Yes, the previous owner cut of the battery and tested with a new one and a bunch o memory sets and VGA. Always the same result. Than he fixed the old battery back (not very well as it had been already cut) and sent the board to me. I removed the battery and cleaned everything . Ext. battery pins are factory not installed - probably because it was a super-cheap design - consider how old 386SX already was when produced. The good quality GP battery is not as dangerous as Varta and it did not cause such a mess. The overal good condition of the board leads me to the assumtion there is an electronic failure../-: However I think the board is salvagable.
Thank you very much for info on that chip and replacement options. Good to know. So one might sey that those ICs are common source of problems? I assume the CMOS part is sensitive.. ๐ I think I am capable replacing that chip. But finding the new one would be an issue. So you think even buying a "lot" of new ones on e-bay is risky? What is killing them - static electricity? Again, thank you!
Unfortunately, I've been noticing quite a few 286/386/486 boards with dying 82C206 chips, so I'd personally say that they have a bit of a failure rate these days.
I don't know why they are starting to die off all of a sudden, I suspect the chips were perhaps a little too integrated for their time, and seriously pushed the limits of their process tech, but that's just my best vaguely educated guess. It's also possible that, since they are part of the ISA bus, they are vulnerable to spikes/surges/etc. and other potentially damaging transients that may afflict the ISA bus. Given that the power supplies (especially the more cheaply-made units) in many older computers are not necessarily aging with dignity, that would seem at least remotely plausible.
I would say you are close to the source of failures. I am now thinking the same way. I have been studying the datasheets for a while now and I think even a faulty or bad seated ISA card can kill it. And well the web information I have found says those integrated chips were not considered 100% reliable at their times - as you states - "integrated and pushing technology to the limits" - you are most probably right. And what hits my nose now - they have to keep the bios setting anc clock thus tey are still powerd from the battery. This board is so simple that there is not much to protect anything and the chance to kill the chip directly is probably higher. I have found an info these chips were often socketed in the past to make repair of expensive motherboards easier. However this board most likely was not so expensive in 1994 as his bulky older predecessors . But I have weakness for those cute compact mobos so will do my best (-:
