Lindbergh yellow boot issue

[Arcade-Projects]

Hi,

I recently bougth a lindbergh yellow and at first it was running fine so that I started to do some software related testing.

But the system sometimes froze, than sometimes it did only boot after some attemps and finally did not boot at all.
With "not booting" I mean that there is no output at all from the video card (no bios screen), there are no reaction to pressed keys (e.g. num-block can not be switch on/off), no beeping, no reaction when I presse reset etc. What happens is that the power is switched on and stayes on so that all fans are spinning, hdd starts spinning , leds are led and everything seems to be powered.

I already tested the following things:
Hardware
- (Removed all non essential hardware so that only cpu, ram, mobo and videocard is left)
- Swapped ram banks and used other rams -> No change
- Swapped P4 against a supposedly running P4 (same stepping) bought from ebay -> No change
- Swapped videocard -> No change
- Replaced the cr2023 bios battery -> No change
- Did a bios reset using the jumpers -> No change

Power related
-Used another PSU -> No change
-Measured the voltages coming from the PSU and the "Power-Good Singal" when the system is powered -> Seems ok
-Mesured the CPU voltage and the "Power-Good" signal of the ISL6556 responsible for the multiphase pwm control of the CPU power supply -> Seems ok (so no broken FETs)


Just when I thought about giving up the system startet booting again and after some trial and error and putting the rest of the hardware back together I even got the game running that is installed.
After a while there were some freezes again and now finally I'm back at not booting event with multiple attemps.

-> It is very likely that the mainboard has a hardware related issue. Maybe a bad solder joint or something similar...

So did someone have a similar issue before and eventually got it fixed?
Any ideas or suggestions what might help to find the issue?

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