Get TOMB3DEM and test it in pure DOS. No drivers needed as it accesses the Voodoo1 directly.

https://archive.org/download/tomb3dem/tomb3dem.zip

Black screen and blinking led from my monitor (old LCD)

This is no good. It should show 3dfx spinning logo and load the game demo. I just tested one Monster 3D and works fine on LCD too.

There was a thread on Vogons about troubleshooting with logging.

kixs wrote on 2023-12-15, 19:21:

This is no good. It should show 3dfx spinning logo and load the game demo. I just tested one Monster 3D and works fine on LCD too.

There was a thread on Vogons about troubleshooting with logging.

For now i will try to reflash the card, God knows what crazy ass solutions i found over the years here on vogons, it might work but since the card is detected and it installs i think the BIOS should be the issue here.

Look here:
Voodoo 1 with "TMU PowerOn Sense: 0xdead", "Board 0: Bogus number of TMUs (57005)!" & "ERROR: b_sum=0x060 r_sum=0x030"

Looks pretty weird, 2mb? Also the software part should be there.

Before jumping into weird hoops, grab glide2x.ovl from your drivers and drop it inside the 3Dfx Tomb Raider demo or any other Glide DOS game you may have and test it out that way.

Nope, even with the ovl in I get a black screen.

I took a glance at the card, it seems like it was missing 3 caps near the ram, I took equivalent ones with a higher voltage and put them in place.
Still the same issue, still only 2 megs perceived.

Try gently poking all the TMU&FBI pins and see if any are loose.
There's also no BIOS on these cards.

sdz wrote on 2023-12-15, 20:25:

Try gently poking all the TMU&FBI pins and see if any are loose.

They feel perfectly soldered and look perfect too.

Perhaps missing/cracked resistors. Some of them are quite important.

sdz wrote on 2023-12-15, 20:32:

Perhaps missing/cracked resistors. Some of them are quite important.

I checked, resistors seems to be all there and in good conditions too, only caps were missing but i replaced them.

More pictures

2MB is normal - that's 2MB for the framebuffer and 2MB for textures on the 4MB Voodoo 1 cards.

Your mojo result is 100% looking good so the communication between the PCI bus, TMU and FBI chips are each working. The RAMDAC is responding correctly since mojo will throw serious errors if it isn't - but what mojo can't tell is whether the RAMDAC's analogue side is properly powered and hooked up.
You stated in the 1st post that you're using the loop cable into your 2D card so the VGA port and VGA pass-through functionality are functioning and it's just 3d mode that's giving a black screen.

Please check the pins on the RAMDAC for anything that looks suspect: https://retronn.de/ftp/docs/pc_hardware/DACs/ICS5342.pdf
Pins 43 & 44 are the power inputs for the analogue side of the RAMDAC. You should also probably check the inductors (FBx & GFBx) dotted around the RAMDAC area to make sure none of them are cracked and that each one has 0-ohms resistance, that's pretty common for those to get broken or go missing especially since it's been stored in such a way that capacitors were broken off.

Also when testing tomb raider in dos, make sure it's not a windows dos-box and that you've fully exited to dos, or boot into command line only to run it. This could still be a driver issue.

Also try without the pass-through cable.

I test it like this:
Pure DOS, go to Tomb3dem directory. Type TOMB. Switch the VGA cable from 2D card to 3dfx card. Press enter to run Tomb3dem. It should show spinning logo and run the game.

I'm the meantime here's more pictures.

Even without loop cable I get a black screen, it's really weird because the card gets warm just right.
Just to make things clear a voodoo 2 was previously installed in the system, is it possible that dos still has some entries that conflict with the voodoo 1?

Well if it is a driver problem then you should still be able to run tomb3dem from DOS.
Going from Voodoo 2 to Voodoo 1 on my win98se test install required doing this: Uninstalling the Voodoo 2 driver, manually clearing all files in the Windows directory that match the files in the V2 driver folder, clearing all 3Dfx registry entries, helped in my case. Then the Voodoo 1 drivers could be reinstalled and they no longer caused a crash. Alternatively just reinstall Windows