Check that the main chips are still level and that there aren't any solder balls that have joined up underneath - that can easily happen with leaded solder at that temperature I think. They could work again if the Voodoo 3's VSA-100 chips are re-balled and reinstalled.

If that's the cause it's beyond my ability to repair it. I don't have proper tools nor experience to do re-balling, I couldn't even solder one PLCC chip without destroying the cards. Is there someone who would attempt to repair them? I would gladly part with one of the cards as a reward.

Why not post some pictures, maybe we can spot anything? Have you tried looking at the BGA array between the chip (substrate) and the PCB? Can you see any balls that have melted together near the EEPROM?

Also instead of removing VGA BIOS chips you can just reprogram the EEPROM with another BIOS.
Actually this gives me an idea:

Have you tried booting the computer with the V3 installed but using some PCI graphics card as your primary video card?
If that works maybe you can try flashing the V3 BIOS. I have attatched the required BIOS files and flashing program. Only use it in real DOS though!
But maybe try posting a picture of your cards first. 😀

Thanks for the tips. I have tried to use both V3s as secondary card while using primary PCI card but with the 3000 the OS froze and with 2000 the system behaves like nothing is inserted in the AGP slot. I have checked the soldering under both video chips and at least those balls around the corner are fine, none of them are jointed. Of course some could be in the middle but I have no means how to confirm that. It is possible at all to melt solder under video chips while I couldn't even melt the solder around BIOS chip? Seems unlikely to me. I have probably fried some other small SMD component.

Here is detailed photo of V3 2000:

And V3 3000:

EDIT: Those oscillators are suspicious. Commonly they're not built to withstand high temperatures above 200°C for a long time. I used 300°C for a minute and something so it's worth a shot.

I don't see any obvious faults on the board either.
I guess replacing the oscillators is a good start. 300°C over a minute is definitely a bit on the warm side.
The OS crashing when trying to load/install drivers for the card makes sense with a malfunctioning clock generator. It also makes me suspect the card isn't completely fried.
Good luck! 😀

Btw: Are you able to reprogram the EEPROM with the correect VGA BIOS for any of both cards under real DOS with the flash tool I posted?

I've tried to replace oscillator on V3 2000 with another one from my other dead card and no luck. I had to use heat gun again as those are SMD oscillators and they are too hard to remove with just soldering iron.

Considering BIOS flashin, non of the cards are getting recognized by the utility anymore.

EDIT: Another dead card... This time Geforce 2 Pro 64 MB. Tried to remove glued heatsink and damaged the chip below. I should just stop bothering anymore.

I don't have energy left to deal with this stuff. If anyone is interested, I will give away both cards for postage costs. I have to make a break.

EDIT: I'll take a break for few weeks and will try to fix the cards again. If that fails then I'll give them away. Some people already contacted me so I will let them know first.