Kahenraz wrote on 2023-12-03, 06:48:

So the card is mostly working but there is no video output.

Corrupted VBIOS maybe?

In this video @vswitchzero managed to repair a couple of Voodoo 3 cards which had similar symptoms by simply re-flashing them.

I flashed the BIOS with no change.

I've attached a backup of the original image.

Check all the inductors near the VGA port. If you have a scope, check for signals on the R, G, B and H/V-sync pins.

C84 next to the main IC doesn’t look like it’s connected at both ends.

paradigital wrote on 2023-12-03, 13:52:

C84 next to the main IC doesn’t look like it’s connected at both ends.

It is. The ceramic capacitor there is just lopsided.

IIRC, in vswitchzero's videos he uses verbose diagnostics logs to determine point of failure in Voodoo cards he has repaired.

Perhaps that could shed some light on where there might be a failure?

Out of curiosity, I setup the Voodoo 3 as a second desktop, opened a window on it, then dragged it over to another desktop that is being rendered by a different card. This produced a garbage rendering of the window. My guess is that this garbage was bit blit from the Voodoo framebuffer, which appears to be corrupt.

Although this isn't a definitive test, it does add some credibility that the fault may be in whichever memory chip serves the framebuffer.

Are there any suitable replacements for this chip or will I need to salvage one from another card?

I have some questions:

1. Are the damaged capacitors replaced? Looks like they got baked in an oven and the electrolytics will probably all need replacing. I mean you've said you have but just checking 😀

2. So in the card's current state, what happens if you boot the computer with just the V3 PCI fitted? Does it boot with no display output, or does the PC give the "no VGA detected" beep error?

3. You've flashed the BIOS, was that through the flash utility in DOS to write the VBIOS while the card is running, or was the EEPROM chip removed to program it?

4. I agree with the suggestions to check the VGA connector with an oscilloscope while the card is running. I don't like pulling out my scope so instead I use my multimeter's (UT61E) Hz / clock measurement mode to see if VSYNC & HSYNC clock signals are detectable. If you have a multimeter with a similar capability I recommend jamming a pin into the VSYNC / HSYNC pins on the VGA port and measure that with just the positive probe.
Even with bad memory or maybe even no memory, the card should be providing video output.

5. I made a floppy image with VMTCE configured for logging to file. That should help you to see if the card is running enough to run this test. See this post: Re: Accurately troubleshooting video memory faults with VMTCE

Something to add as well, the framebuffer and card's memory layout is not confined to one chip. Because the V3 has a 128-bit bus, that's made up in aggregate from all 4 of the QFP SGRAM chips with 32-bits each.