How is that card supposed to work on the ISA bus!? Apart from the burnt trace, which seems like a clear indicator of a short circuit, the card seems to connect the following ISA pins only

• RESETDRV - to display the reset signal.
• +5V/GND for power supply (LEDs, control chip)
• D0-D6, no D7!
• not a single address bit!
• IOW (to monitor I/O writes)
• MEMR (maybe for a LED that shows BIOS access)

The burnt trace connects pins B1, B10 and B31. All of them are supposed to be ground pins. If the card was inserted in the right orientation (i believe you that you got it right. You know where to expect the component side of an ISA card), and in exactly the right position, connecting the three ground pins can not cause any damage and can not lead to burnt traces. But take a look at how short the ISA connector is on that card compared to an regular ISA card, you will likely discover that the unused PCB space left and right of the 31 connections each side is missing. This allows the card to be misplaced by half a pin at least. Now that makes some sense. Pin B9 is +12V. If you short +12V into something expecting 5V at max, you might very well get damage! If the pad for Pin 10 touched pin 9 well enough to pick up +12V, but pin 10 badly enough to not short the +12V out in-place at that position, the pad for pin B31 most likey connected to pin B30 instead. That sounds like very bad news 🙁, because that pin is OSC, the 14.318 MHz main oscillator of the IBM PC, also clock source for the IBM CGA card. This pin is mostl likey directly connected to the OSC input on the PIIX3 south bridge (pin 136), which will not like +12V on that pin at all.

Something must have shorted the +12V from the supply towards +5V or GND to cause the trace to burn. That device that shorted the +12V line might have just used the internal protection diode for that, so the +12V were shorted into +5V. But the protection diodes are made for a couple of milliamps, not a couple of amps. So it likely overheated and caused collateral damage. The source for the OSC signal is most likely the main clock synthesizer chip. That clock synthesizer chip seems to still be alive and kicking, otherwise your system most likely wouldn't power up at all, but if you are lucky, just that chip is damaged. That's the "PhaseLink" chip next to the Dallas chip on the P55T2P4, which can be swapped by hand soldering (with some experience!).

A first step for damage assesment would be to check the OSC line on the ISA bus (B30) for shorts to +5V (B3) or GND (B1), because an overheating protection diode might have gone short. Also you might want to check the trace for OSC on the mainboard for burn marks, especially interesting is to find out, what parts are burnt and what parts not. It is likely that the end of burn on the OSC line (if there is any) is indicating what chip caused the +12V to be shorted out.

Thanks.

There is a printed hint "PC Back Side ->" on the PCB.
Are you sure that you haven't inserted it in the wrong way?

Perhaps it will still work on PCI, but no more on ISA.

I have a card similar to this. PCI is fine, ISA didn't work at first but nothing bad like that. Then I inserted it the correct way and it worked. By rear it means rear of the PC and not the rear of the slot.

RichB93 wrote on 2020-10-09, 23:12:

I have a card similar to this. PCI is fine, ISA didn't work at first but nothing bad like that. Then I inserted it the correct way and it worked. By rear it means rear of the PC and not the rear of the slot.

I also have a copy of that card. In contrast to the card in the original posting, this card has a proper width ISA edge connector that prevents misaligned or tilted insertion into the slot. I stopped thinking about what kind of "rear" they mean and I just go by "on what side would the components be on a regular ISA/PCI card" and plug that card the same way. I don't even bother looking for the "rear --->" mark any more.

I have that same card pictured above as well. Only have used it a few times but it has never given me problems. The one in the OP looks like a really cheap version of the already cheap Chinese post card like the ones we have.

RichB93 wrote on 2020-10-09, 23:12:

I have a card similar to this. PCI is fine, ISA didn't work at first but nothing bad like that. Then I inserted it the correct way and it worked. By rear it means rear of the PC and not the rear of the slot.

I have a similar ISA/PCI POST card (with 5 logic chips) and in it's manual it states: If inserted wrong direction in ISA slot it can cause damage to card, motherboard or both.
I too once put it in wrong in an ISA slot but it did no damage to anything,

cyclone3d wrote on 2020-10-09, 23:46:

I have that same card pictured above as well. Only have used it a few times but it has never given me problems. The one in the OP looks like a really cheap version of the already cheap Chinese post card like the ones we have.

Agree ! the OP's card has just one logic chip so assume it is a lessor quality product than the 5 chip versions.
Also in the manual it states that: some motherboards will not give proper codes from ISA slots if PCI slots are present depending on BIOS and chipset.

cyclone3d wrote on 2020-10-09, 23:46:

The one in the OP looks like a really cheap version of the already cheap Chinese post card like the ones we have.

They should sell this ultra-cheap edition as PCI only and do away with the broken ISA connector. It misses at least 9 connections to the ISA bus (A0-A3, A6-A9, D7) that are necessary for kind-of proper operation (real proper operation would also decode A4,A5,AEN), so I don't see how it will ever work in an ISA slot. This applies even if you manage to align it correctly. Seems like they didn't finish the ISA side of the card until production time.

I would recommend lolo799 to use a compact angle grinder like a Dremel to remove the dangerous and non-functional ISA connector from the card to prevent accidental killing another main board. Is an ISA post card is needed, by the "real thing" instead of the cheap clone of the common cheap card. As it looks, the PCB is 2-layer only, so using an angle grinder does not risk shorting internal layers. Looking at the possibility of inner layers in more detail: They did connect the three GND pins and they did connect the two +5V pins on their attempted ISA bus card egde - but the did not connect that to the power rails of the card. Also: they installed the speaker, but "forgot" to install the 2-pin header for the cable to the mainboar speaker output. Just WTF?

Thank you mkarcher for that very informative reply.
I noticed the shortness of the ISA connector and I think I carefully put in the slot so the pins would be aligned, but I still may have made a mistake there.
As for your first observation, it was a cheap product from an over abundance of cheap clones on ebay, it's a bit ironic that I broke a perfectly working motherboard I got new in the mid 90s with an add-on card made to diagnose hardware issues, there's a worthy lesson here...

And don't worry it will never get close to an ISA slot ever again!
I'll take note of your suggestions on what to check for signs of damages on the board, and take pictures along the way in the coming days.

Disruptor, RichB93 and Horun, it definitely was in the correct orientation.

Hey guys,

I got the same card as OP (A311L5G1112), started searching the web for the manual but no luck so far.

Anyone perhaps has a link to manual (or a link with post codes will do), the one that came with it is in chinese...

Thanks in advance 😀

Khorne wrote on 2020-11-03, 19:07:

I got the same card as OP (A311L5G1112), started searching the web for the manual but no luck so far.

Anyone perhaps has a link to manual (or a link with post codes will do), the one that came with it is in chinese...

The POST codes do not depend on the card you use, but only on the kind of BIOS. The leaflets provided with the cards only have limited use - in the best case, they just copy a good set of POST code references from the web, in the worst case, they copy some POST code table without even telling you what BIOS they apply to. http://www.bioscentral.com/ seems to have a comprehensive set of POST code tables.

mkarcher wrote on 2020-11-03, 20:38:

Khorne wrote on 2020-11-03, 19:07:

I got the same card as OP (A311L5G1112), started searching the web for the manual but no luck so far.

Anyone perhaps has a link to manual (or a link with post codes will do), the one that came with it is in chinese...

The POST codes do not depend on the card you use, but only on the kind of BIOS. The leaflets provided with the cards only have limited use - in the best case, they just copy a good set of POST code references from the web, in the worst case, they copy some POST code table without even telling you what BIOS they apply to. http://www.bioscentral.com/ seems to have a comprehensive set of POST code tables.

Ah, I see. So what you are saying is it will depend on the board / chipset what the output code will mean. That actually makes perfect sense when I think about it 😀
Thanks !

Just to add my two cents.
I've bought the exact same card to troubleshoot an old 486 ISA only.
It was not working (no light)
I just test it on a known working HP vectra P133 :
Ok in PCI slot
Not OK at ALL in ISA : no light + preventing boot (and i have put it in the right direction ^^)

might as well add my 2 cents....

The one chip card is in no way usable for post codes on the isa bus.
the chip is not even connected to the isa bus.
I bought one, tried it, removed the chip and noticed the traces just ending there.