Are there any burnt traces or burnt spots on any of the chips?

I have a identical 3d monster that works so today I did a quick comparison side by side.

What really sticks out is the resistance from the output and input vga port pins to ground.

So on my working card I get alot of pins that show .500 resistance to ground, on the faulty one it shows .50 .. this is a big difference almost like something is nearly shorted to ground on that line.

Without a schematic (not like anybody has it) for a 3dfx its a guessing game where the line goes or can't even see anything burned.

Some of the port pins are connected to the
p15c3384q chip on the back, has anybody got any experience here or what would most likely get shorted out here first?

Talking about the area between C16 and R36
and u can see those traces go to vga out

Using a multimeter, test pins 12 and 24 of the P15C3384 10-bit 2-port bus switch chip there.
If they are shorted, then try removing the chip and re-testing the pads for pins 12 and 24. If they're still shorted, the fault is elsewhere (and you can put the chip back in). On the other hand, if the short is cleared, the P15C3384 is probably the problem chip.

Pin 12 is short along with many pins between 1 and 12. Also I found shorts on one of the main chips on the front

I got shorts on cvdd and dvdd which are clock power inputs according to the pinout.

I guess from here it comes down to removing part by part to see if it clears the short and the bus switch is smaller and easier to take off.

I could probably keep turning it on and see what gets hot but don't know if its worth stressing it out more.

I will take off the bus switch when I have some time.

CVDD and DVDD are often connected together I think?

I took off the bus switch chip, now the resistance on cvdd is .450~ looks much better! it is .350~ on the working card but with the bus switch naturally it won't be exactly same.

Now the big challenge will be finding a replacement

strictly speaking you don't have to have the switch - you could bridge the Voodoo's DAC directly to the output DE-15 and just not use the passthrough

then handle switching externally with an Extron VSW 2VGA A

If I had that hardware would be a good test to see if it works with the chip off. I have ordered the chip from ali express for about 3usd so now it will take a few weeks

Good luck. It's pretty hard to find legitimate/working chips on Aliexpress. I don't even order from there anymore because I've received too many fakes or factory 2nds with broken functionality. If the chip doesn't work, look for a used board that has the same one and transplant it.

for 3usd its worth the gamble but I am of the same opinion.

I don't have any other broken 3dfx, anybody have any idea on what other old cards or electronics I could find this chip?

wiretap wrote on 2021-06-24, 12:46:

Good luck. It's pretty hard to find legitimate/working chips on Aliexpress. I don't even order from there anymore because I've received too many fakes or factory 2nds with broken functionality. If the chip doesn't work, look for a used board that has the same one and transplant it.

YMMV
I ordered an SMC FDC37c932FR and a winbond w89c982af. Both are working fine. My mainboard's keyboard&mouse are working fine again, as well as my 10Mbit HUB :-p
on the other hand, I ordered some MPF102 transistor, which don't match the datasheet pinout.

edit: just to add the correct chipid is PI5C3384q , not 15. This way google will find it 😉

treeman wrote on 2021-06-24, 09:43:

If I had that hardware would be a good test to see if it works with the chip off. I have ordered the chip from ali express for about 3usd so now it will take a few weeks

you don't need a switch to test it, just manually move the monitor cable after the game switches to glide mode

it certainly won't work with the chip simply removed though, you will have to bodge over the signals

maxtherabbit wrote on 2021-06-24, 15:15:

treeman wrote on 2021-06-24, 09:43:

If I had that hardware would be a good test to see if it works with the chip off. I have ordered the chip from ali express for about 3usd so now it will take a few weeks

you don't need a switch to test it, just manually move the monitor cable after the game switches to glide mode

it certainly won't work with the chip simply removed though, you will have to bodge over the signals

or just attach a second monitor to the card, just for the 3d output. right? easier than switching over, though still requires bodging the signals.

weedeewee wrote on 2021-06-24, 18:38:

maxtherabbit wrote on 2021-06-24, 15:15:

treeman wrote on 2021-06-24, 09:43:

If I had that hardware would be a good test to see if it works with the chip off. I have ordered the chip from ali express for about 3usd so now it will take a few weeks

you don't need a switch to test it, just manually move the monitor cable after the game switches to glide mode

it certainly won't work with the chip simply removed though, you will have to bodge over the signals

or just attach a second monitor to the card, just for the 3d output. right? easier than switching over, though still requires bodging the signals.

Yeah this is a great idea, so simple and logical!

Just tried it but got no signal 🙁

However the card is detected by the system so it is not totally dead.
This is what I did:
1. start system with video connected to 2d card (s3 trio)

test 1
2. boot to dos
3. start shadow warrior 3dfx patch
4. turn off power to monitor
5. switch cable from s3 trio to 3d monster
6. turn on monitor, no signal
7. when press keyboard can hear the sounds for the menu moving.

Test 2
1. take out 3d monster, only 2d card in system
2. start system in dos
3. start shadow warrior with 3dfx patch
4. error no card detected

Test 3
1. put 3d monster back in
2. connect vga to 2d card (s3 trio)
3. start Windows 98
4. check device manager and shows 3d monster works ok

After the tests I took out the 3d monster the 3 main chips were warm, not hot so I think this is a good sign.

I guess it looks like somewhere along the path the 3d signal is not going out to vga port, hope its not the main chip 🙁

Any tips what I can test next?

I will keep the switch chip off now, I did have shorts with it so it is still questionable

Again, it's not going to work with the switching chip simply removed. You have to manually solder wires from the DAC input side of the switch ship's footprint to the connector output side

I see, I do remember now reading that at the very start but got excited and jumped the gun.

Its not straight pin to pin connection from input to output? (where chip was) That would be too easy?

treeman wrote on 2021-06-25, 02:02:

I see, I do remember now reading that at the very start but got excited and jumped the gun.

Its not straight pin to pin connection from input to output? (where chip was) That would be too easy?

Bro I don't think you're picking up what I'm putting down. You might be better off just getting a new chip and installing it. Just randomly connecting pads to other pads is a good way to smoke something

maxtherabbit wrote on 2021-06-25, 02:37:

treeman wrote on 2021-06-25, 02:02:

I see, I do remember now reading that at the very start but got excited and jumped the gun.

Its not straight pin to pin connection from input to output? (where chip was) That would be too easy?

Bro I don't think you're picking up what I'm putting down. You might be better off just getting a new chip and installing it. Just randomly connecting pads to other pads is a good way to smoke something

That and checking (and likely fixing) the potentially broken traces, if you do replace the chip .

As mentioned by maxtherabbit, do no connect the chip pads together. The missing chip was not a passthrough resistor block .

I know what your saying, the input side of the switch needs to connect to the output side to the vga out, just like the chip would switch that output - for the 3d.

Ofcourse there will be a vcc pin and if connected to the wrong pin it will smoke it.

So I have no idea at this stage which input goes to what output. I can probably use a multimeter to try determine this on my working 3d monster, unless somebody already mapped this or knows? This is what I was trying to imply