u missed last post- i already killed this board 😒

dulu wrote on 2022-11-19, 20:30:

u missed last post- i already killed this board 😒

Sorry for your loss, in a few days you'll feel much better.
Been there.

It didn't work anyway. If it's worse than before then you can use it at least for spare parts - slot 1 retaining clips, chipset heatsink, ISA slot (some boards miss it), BIOS chips etc. Also use it for practicing capacitor replacement.

I have a BX2000 that stopped posting some time ago. I recapped it but it made no difference.

I came across this thread and decided to remove the BIOS chips and reflash them just in case. It didn't help.

No components get hot as far as I can tell. I have a ISA POST card that tells me the 12V/-12V/5V lines are ok, but nothing else.

Any more ideas of what to try (how)?

dulu wrote on 2022-11-19, 20:14:

When measuring the voltage on the isa connector, the board turned off - I think I made a short circuit ... Mobo stopped starting at all. There is a short circuit on the 5V line. I desoldered the RAID chip - still shorted. I connected the battery to the 5V line to check which element will heat up - the south bridge gets hot. So I think it's over.

RIP to your board

tauro wrote on 2022-11-25, 04:35:

I have a ISA POST card that tells me the 12V/-12V/5V lines are ok

sadly no, POST cards can only indicate mere presence of some voltage on those power rails. Im not aware of any POST cards intelligent enough to even measure, not to mention analyze (for ripple, sags). Not that is the problem with your board, just throwing it out there so people dont get the wrong idea about those cards.

no codes means CPU is not starting at all, or is unable to read bios. Bios goes thru southbridge on 440BX boards.
cpu needs ~2v power, 1.5 Vdd (first pin on socket1). Chipset needs 3.3V. Southbridge and bios need 5V.

rasz_pl wrote on 2022-11-25, 04:58:

tauro wrote on 2022-11-25, 04:35:

I have a ISA POST card that tells me the 12V/-12V/5V lines are ok

sadly no, POST cards can only indicate mere presence of some voltage on those power rails. Im not aware of any POST cards intelligent enough to even measure, not to mention analyze (for ripple, sags). Not that is the problem with your board, just throwing it out there so people dont get the wrong idea about those cards.

Thanks for that info. Of course now that I think about it, it's so simplistic to say everything is fine based on a POST card xD
I guess that it just reports if it has a steady voltage but that doesn't mean much.

rasz_pl wrote on 2022-11-25, 04:58:

no codes means CPU is not starting at all, or is unable to read bios. Bios goes thru southbridge on 440BX boards.
cpu needs ~2v power, 1.5 Vdd (first pin on socket1). Chipset needs 3.3V. Southbridge and bios need 5V.

Thanks for those ideas. I measured the VCC on the BIOS chips and they get 5v.
On the slot 1 I measured A1, and it's 1.5v. But B13/B17 is giving only 0.8v. I guess that's wrong, isn't it? That should be at least 2v, right? What could be the cause?

measuring wrong pin would give that voltage for sure 😀 or bad caps 😀 third option is slotket with bad jumpers
just to be sure measure vcore on the big coil next to the chipset

I'm measuring the contacts on the bottom side of the board. I did first it without a CPU, and just did it again with a CPU, and it's the same voltage.
As you told me I also measured the coil and GND, and it also shows this same voltage.
It starts at about 0.5v and goes up to 0.8v.

To be completely sure, I just did it on a different board, a SY-6BA+III and I measure 2V (B13/B17). I'm using this reference http://ps-2.kev009.com/eprmhtml/eprma/f706.htm
Do you think this is a caps problem? I remember replacing all the caps on the board. I may have made a mistake because I'm learning and this was some years ago.

I'm thinking, could it be related to the MOSFETs, in which case, how could I discard them as the culprits?

I need a good i440BX board because the SY-6BA+ (III and IV) for some reason won't cooperate with a USB keyboard.

Thank you very much for your help! It's greatly appreciated 🙏

same weird voltage without cpu looks like broken vcore circuit. its designed in a way to not produce any if all VID pins are floating.
you can buzz mosfets in diode mode looking for a short. Short on upper one would maybe briefly send 5V to the CPU then trigger OVP, short on lower one would trigger OCP. RC5051 is blown? https://datasheetspdf.com/pdf-file/354866/Fai … ductor/RC5051/1

I had somehow the same issue with my BX2000. Noticed the switching power passes on the board around PS/2 ports. Mine was a cold solder/Micro PCB disconnecting under it. Fiddling with the PS/2 connectors and cables brought it back to life. You might check if your issue is something similar.

I found those BX2000 boards made with not so high quality as the silly failure rates are generally high on them.