I was re-flowing the chipset using my hot-air gun and flux so far but I will try the iron as well. Adding fresh tin to the pads will at least help me by removing the chipset if necessary. I will do this at first although I have checked all pins by pressure already twice - still a cold joint could be present.

The idea about the chipset swap is good, will take lots of time and of course I can damage either the chipset or the mobo during this but it is wort the shot.
I will start with the tinning and then find some time to do this. The damaged chipset is something I do not want to repair but I was already grinding and adding new pins to one chipset in the past, took a quite long time but it was possible. Maybe there is hope in that as well.

thank you for your help, I got some very useful tips I can apply later on on other boards 😀
will come back to this when I will finish that or that step.

thx, tomas

just a quick update, I have re-soldered all the legs of the chipset using my iron but without any difference, still stuck in reset with no CLK on the ISA slot.
Also, I have broke the trace on the damaged board that went from the 7407 pin 6 to the chipset, the board was stuck in reset after, however, the CLK was still present on the ISA slot. This worries me since the chipset on the nice board seems to be too dead 😁

just to make it more clear, the damaged board is missing the: CPU, KBD bios, BIOS, RTC, OSC for both the 14MHz and 32kHz --- still it will release the reset and provide CLK to the ISA slot. While interrupting the POWER GOOD, the reset is stuck but CLK to ISA slot is still working.

Does the newer board work without those chips?

MikeSG wrote on 2025-06-23, 11:10:

Does the newer board work without those chips?

the newer board is not posting at all and is stuck in reset. The newer board, images in post #1, has all ICs and visually is in great condition. However, there is no CLK to the ISA port, and the board is in RST stuck.
the older board is almost the same as this one, a kind of clone, missing the CPU, both OSC - the 66MHz is still there, missing KBD bios, RTC, Bios, a few traces eaten away, the chipset missing 4x legs... still, the chipset provides the CLK to the ISA port, and the board is releasing RST.

br, tomas