just tested the relays for good measure and they click over as expected when 5v is applied to the coils...

Here's another question ... does anyone know how many layers this board is? The damage to the traces on the back of the card was quite deep... is it possible that I have broken traces buried in the board layers that I cannot see? The damage is just above where the TMU is on the otherside of the card.

It looks like a normal 4-layer board with gnd/pwr planes in the middle to me.

One thing I tend to do is to test the solder connections on the TMU:s type of pins, is using a fine needle or toothpick, just slide it gently along the legs and listen for the 'ping' that indicated a good solder attachment, if a pin is loose from the pad it will not make the same sound.

Check for cracks in the soldering under the memory chips pins.

Rwolf wrote on 2025-11-06, 17:58:

It looks like a normal 4-layer board with gnd/pwr planes in the middle to me.

One thing I tend to do is to test the solder connections on the TMU:s type of pins, is using a fine needle or toothpick, just slide it gently along the legs and listen for the 'ping' that indicated a good solder attachment, if a pin is loose from the pad it will not make the same sound.

I've reflowed both 3dfx chips and checked pin by pin under the scope. They're sound.

Postman5 wrote on 2025-11-06, 19:37:

Check for cracks in the soldering under the memory chips pins.

checked as well - all super sound

Lostdotfish wrote on 2025-11-06, 15:06:

Here's another question ... does anyone know how many layers this board is? The damage to the traces on the back of the card was quite deep... is it possible that I have broken traces buried in the board layers that I cannot see? The damage is just above where the TMU is on the otherside of the card.

I have checked pretty much everything I can check now... I am leaning towards thinking there must be damage to a trace in one of the inner layers of the board. As far as MOJO is concerned - the TMU does not exist nor does any of it's attached memory...

This is the trace repair - it is directly behind the passives at the top of the TMU. The cut is quite deep...

Wish I had a spare TMU so I could swap test that and see if it is actually dead or not...

You didn't mention whether You have tested the voltage to the TMU? which I assume will be on the +ve of c43.
My Diamond monster had a bad memory chip that caused the TMU and/or FBI to get quite hot when I was testing it.
Check all the network resistors in ohms mode, if even 1 has gone high that could be it.

Imperious wrote on Yesterday, 00:36:

You didn't mention whether You have tested the voltage to the TMU? which I assume will be on the +ve of c43.
My Diamond monster had a bad memory chip that caused the TMU and/or FBI to get quite hot when I was testing it.
Check all the network resistors in ohms mode, if even 1 has gone high that could be it.

I popped the card back in my test system so that I can get a meter on it while powered.

All the yellow caps have 5v where expected.

All the TMU RAM ICs have 5v on pin 1

The TMU has 5v on pin 153

So I have to assume that TMU and RAM are all powered correctly.

MOJO output looks like this.

and logging

1sst1Init Routines: InitCode $Revision: 8 $
2sst1InitMapBoard(): BoardsInSystem = 1
3sst1InitMapBoard(): vAddr:0xe6000000 pAddr:0xe6000008 Dev:0xf Board:0
4sst1InitRegisters(): Setting TREX-to-FBI FIFO THRESHOLD to 0x8...
5sst1InitRegisters(): Setting PRELIM FT-CLK delay to 0x8...
6sst1InitDacDetect(): Entered...
7sst1InitDacDetectICS(): Entered...
8dacWr(0x7,0xb)
9dacRd(0x5,0x79)
10dacRd(0x5,0x2e)
11dacWr(0x7,0x1)
12dacRd(0x5,0x55)
13dacRd(0x5,0x49)
14dacWr(0x7,0x7)
15dacRd(0x5,0x71)
16dacRd(0x5,0x29)
17sst1InitDacDetectICS(): Exiting...
18sst1InitRegisters(): Storing TREX0INIT0=0x5441
19sst1InitRegisters(): Storing TREX0INIT1=0xf420
20sst1InitRegisters(): Storing TREX1INIT0=0x5441
21sst1InitRegisters(): Storing TREX1INIT1=0xf420
22sst1InitRegisters(): Storing TREX2INIT0=0x5441
23sst1InitRegisters(): Storing TREX2INIT1=0xf420
24sst1InitSetGrxClk(): Entered...
25dacWr(0x7,0xe)
26dacRd(0x5,0x0)
27dacWr(0x4,0xa)
28dacWr(0x5,0x7b)
29dacWr(0x5,0x6c)
30dacWr(0x4,0xe)
31dacWr(0x5,0x0)
32sst1InitRegisters(): Setting up FAST DRAM Configuration
33ERROR:  b_sum=0x030  r_sum=0x060
34sst1InitFillDeviceInfo(): Retry #1 for chip GetInfo()...
35ERROR:  b_sum=0x030  r_sum=0x060
36sst1InitFillDeviceInfo(): Retry #2 for chip GetInfo()...
37ERROR:  b_sum=0x030  r_sum=0x060
38sst1InitFillDeviceInfo(): Retry #3 for chip GetInfo()...
39ERROR:  b_sum=0x030  r_sum=0x060
40sst1InitFillDeviceInfo(): Retry #4 for chip GetInfo()...
41ERROR:  b_sum=0x030  r_sum=0x060
42sst1InitRegisters(): ERROR filling DeviceInfo...

Still stuck but obviously something not happy when setting up the DRAM but I guess if the TMU isn't talking, then it can't bring that RAM online...

see my repair post here for some ideas 3dfx Voodoo 1 fault diagnosis and repair

You can try and reduce the amount of FBI and/or TMU memory available then test with tomb raider and see if any signs of life are there.
If one of the TMU memory chips is bad it could stop the TMU functioning.

Imperious wrote on Yesterday, 09:40:

see my repair post here for some ideas 3dfx Voodoo 1 fault diagnosis and repair

You can try and reduce the amount of FBI and/or TMU memory available then test with tomb raider and see if any signs of life are there.
If one of the TMU memory chips is bad it could stop the TMU functioning.

I removed the 4 TMU RAM chips and tested the card. Same result - TMU 0xdead

I went ahead and removed the 4 FBI RAM chips as well - so the card currently has no RAM on it at all - still getting TMU 0xdead

I'm going to solder the TMU RAM back into the FBI positions and test again...

What system specs are You testing it on? Voodoo 1 cards generally don't like faster cpus like athlons or p3's above 800mhz or thereabouts.
Do any of the chips get hot when testing. The TMU and FBI especially should be warm at least when powered up.

Imperious wrote on Yesterday, 11:09:

What system specs are You testing it on? Voodoo 1 cards generally don't like faster cpus like athlons or p3's above 800mhz or thereabouts.
Do any of the chips get hot when testing. The TMU and FBI especially should be warm at least when powered up.

I have an immaculate copy of this same card that works flawlessly in my system.

Both TMU and FBI are warm to the touch when the system is on

Progress!

Soldered the TMU RAM to the lower 4 positions.

Going to solder in the other 4 and see if I get funky textures...

So 3D apps now trigger the relays to click over but black screen on output.

Guess we play hunt the faulty RAM module now.

Lostdotfish wrote on Yesterday, 13:45:

So 3D apps now trigger the relays to click over but black screen on output.

Guess we play hunt the faulty RAM module now.

Any idea why I'm getting 1MB reported on the TMU when no TMU RAM is currently installed?

Well, could be that the card's BIOS or the tool does not actually probe for memory but assume it's presence based on possible hardware configurations and 1 MB is the bare minimum.

technokater wrote on Yesterday, 14:13:

Well, could be that the card's BIOS or the tool does not actually probe for memory but assume it's presence based on possible hardware configurations and 1 MB is the bare minimum.

No BIOS on Voodoo 1/2 cards.

Didn't check the hardware, but on banshee that is what the driver does to detect the memory size. According to the datasheet, texture memory can be 1-4 MB EDO DRAM, thus I would assume the tool just uses this as a minimum.