First post, by kaputnik
Discussed my retro rigs in another thread, and got the suggestion to build a Northwood one. Had nothing better to do yesterday, so brought up my old Asus P4P800 Deluxe mobo from the cellar to build something around just for the hell of it. Good way to get the hangover from saturday night out of the mind and kill some time at least 😁
However, the damned thing won't even post. The standby LED lights up when I power on the PSU, and everything looks fine, but when starting the computer, the CPU fan only spins for a fraction of a second, and then dies. When trying to start it again, nothing at all happens until I power cycle it, and give everything time to discharge until the standby LED goes out, before powering it up again.
When I think about it, I have some faint memory of the mobo dieing on me without explanation, and getting my next computer due to it. However, got no idea at all why I would have kept a broken mobo all these years? It's just not like me.
Tried with two different PSU:s, another CPU, other RAM sticks (CPU and RAM verified compatible with the mobo), a few different GPU:s (both AGP and PCI), just in case I remembered what happened all those yeara ago wrong. At this point I'm certain it's something with the mobo. For the record, I did the testing with the mobo out of the case on a non-conductive surface, both with one and two RAM sticks, and nothing else but PSU, CPU, GPU, and a PC speaker connected. The CMOS battery had been removed before stowing away the mobo, fitted a fresh one before beginning. Oh, and I did not forget the 12V CPU power connector 😀
Tried to connect a PCI post card. Unsurprisingly it never shows any error code on the display, but the +3.3V, +5V, +12V and -12V indication LEDs lights up immediately when starting, as they should. Everything but the 3.3V LED goes out once the computer dies again, this should also be in its order.
As an experiment I unseated the BIOS chip. The computer behaves exactly the same way without it. Beginning to think it's some protection circuit either in the PSU's or on the mobo that cuts out the power, very early in the process.
Noticed that the motherboard is slightly warped, and that both the north and south bridges are quite large BGA packages. Tried to boot the computer while pushing them down, to temporarily reconnect any solders the mechanical stress might have broken. Tried to loosen the retaining clips for the CPU heat sink, and also pushing the CPU down. No difference.
The PSU I used back in the days was the one included with the Cheiftec Dragon case. It's known to be of quite low quality and suffer from bad caps, not impossible that fried the mobo.
All caps looks good. Doesn't necessarily mean they are good of course, but there's nothing obvious to the eye at least. Found no visible signs of mechanical damage, excessive heat generation, corrosion, shorts, etc either. The environment in the cellar where I stored it never goes below 10 deg C even in the winter, and it's not damp or anything like that.
I'm out of ideas, besides desoldering all the caps to check ESR and capacitances. My recollection of the mobo just dieing without explanation smells bad caps miles away, but still wanna check if you guys have any suggestions of other things to try before doing that.