Hi everyone,

I've just removed the Pentium 133 and installed an Pentium MMX 166 and now the motherboard nolonger works.

It's this model: https://theretroweb.com/motherboards/s/gigabyte-ga-586s

There's no BIOS POST, the ISA/PCI debug card shows the beep,
but no real error code on the 7 segment display.
An 8 glows, but that might be a bug.

The beep code: a few beeps at the start, then endless short, very quick beeps.
When I remove RAM, the endless beeps won't happen. So the problem is past memory test, I guess.
Maybe voltage/power related?

I did check the motherboard manual before, of couse.
I changed all the jumpers for split-voltage for Pentium MMX (P55C) before testing.

When I measured voltages, the LX8385 and its output voltage was at 3.49v instead of 3.3v.
So I've changed the 120 ohms resistor for an 112 ohms and the output was 3.30v.
Also used the multimeter to check for capacitor shorts (via resistace method).

But still, the endless beeping continues.

I'v also went back to original settings and re-installed the Pentium 133, but no change.

I wonder what's broken.. 😟

Any ideas welcome.

Jo22

Edit: Photos and sound file added.