VOGONS


First post, by Ozzuneoj

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Okay, yet another thread about a defective Voodoo 2. They're getting much harder to come by, so I'm more inclined to try to fix any that I find. This one had no damaged components as far as I could tell. There's a couple of dings in some traces on the back, but I made sure they weren't broken weren't shorting to each other and they seem okay.

When I first tried this card, it was only detected as "PCI Card" in Windows 98SE. This is my tester system which has separate Windows folders for each type of hardware I frequently test, so any Voodoo 2 should simply work (using Fastvoodoo drivers). I took the card out, cleaned the contacts with an eraser and double checked that there were no bent legs on the main chips. I did notice that one pin on the pixelFX chip had a slight bend in it (9th pin down from "128") so I straightened it out a bit. It still isn't perfectly straight but it definitely isn't touching anything.

I put the card back in and when Windows loaded the card was already in device manager, as if it had been there all along (how it should be on this system).

In games however, I get a lot of graphical corruption and it shimmers and moves a lot in Descent 3 (Glide). Another game I tested was a demo of Jedi Knight: Mysteries of the Sith, from 1997, which has much lower requirements.

I can't seem to find the registry entries that people use to disable TMUs for testing purposes... I've read about them, and I've found the 3dfx key in my registry but nothing there mentions disabling a TMU, and no one online that I can find has ever actually said what to edit to do this. My Googles have failed me.

The extent of my troubleshooting has been the following:

* Checked the card with my FLIR One while it's running to see if there are any obviously overheating memory chips, and I haven't seen anything out of the ordinary.

* Pressed on various chips to find any sign of a bad connection. This revealed something rather interesting. When anything is near (not even touching) the upper left corner of the right side TMU, it changes the look of the graphical corruption. I get the same thing with the SMD components on the opposite side of the PCB in that area. If I squeeze the chip\board in that spot the corruption stops moving and becomes static, but still isn't better. Strangely, one of the memory chips on the back also seems to respond to being touched in a similar way but not as dramatically. Since it happens without even touching it, I'm guessing this is some strange effect of EMI or static? I wanted to try with something non-conductive so I tried it with the bristles of a tooth brush (which I use for cleaning cards, not my teeth) and this too seemed to cause the corruption to change, even if the bristles weren't quite touching anything. Very odd.

* I rebooted and tried Jedi Knight FIRST and to my amazement it had no corruption! After playing with some settings however, the corruption came back to certain textures. Ever time I went to the menu (not accelerated) and returned to the game the corruption would switch to other textures. I'm guessing this is video memory related and the reason it works the first time is because the memory is empty, and after that it is filled and is loading data to a bad chip?

Here's a gallery with some pictures:
https://photos.app.goo.gl/dZp6rhEmAz2H35Un6

I'm hoping this is a sign of memory problems, because I think I can replace one of those. I'm far less confident about replacing a TMU... What do you guys think?

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Now for some blitting from the back buffer.

Reply 2 of 7, by Ozzuneoj

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sdz wrote on 2020-04-10, 00:12:

Try gently poking all the TMU pins and see if any of them move.

Holy crap, I did this on the PixelFX chip and thought that I'd done it to the others. 5 seconds after reading your post, I poked the second pin from the left on the top of the TMU and it was loose... yes, it was the first pin I tried! I could have fixed this hours ago! I thought for sure I checked them.

Thank you!

I hate resoldering legs like these because its hard to do it without messing with the ones around them. I should probably learn how to do this with my hot air rework gun but I've only really used that to harvest components from dead boards, never to fix otherwise working ones. I'll just do it the old fashioned way and be extra careful. I hope this fixes it!

Now for some blitting from the back buffer.

Reply 3 of 7, by sdz

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No problem, I hope it works fine after soldering it.
It's not really a good idea to use hot air on such old ICs , the epoxy package had ~20 years to absorb moisture. Just use a small tip on your soldering tool, with a little solder on it (preferably the type with lead in it), and apply flux on the TMU pins, it will make soldering easier and prevent solder bridges.

Reply 4 of 7, by pentiumspeed

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What helps so much is tube of paste flux. This will make the solder so liquid and combine into one nice solder joint instantly.

Cheers,

Great Northern aka Canada.

Reply 5 of 7, by Ozzuneoj

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Thanks guys, I used flux and my trusty Hakko FX-888D and now it's running like a champ! And thank you for the tip about not using a hot air gun. I'll keep that in mind. 😀

I'm not highly experienced with soldering (don't do it as part of a real full time job and never went to any kind of school for this stuff) but I've been doing it here and there for about 17 years, so I'm picking things up as I go. The vast majority of my soldering experience has been gained in the last 4 years since I started getting back into retro PCs. Last year my 6 year old 10ml flux pen\brush was finally running out and everything was suddenly a huge pain so I bought a 4.2 oz bottle of flux since it seemed like the most cost effective way to get it. I must say, this stuff is great! There are probably better quality products out there, but it makes such a huge difference I can't believe I went so long with the same 10ml squishy pen of crappy watery flux. I just refilled the brush\pen for the time being (pulled the end off and poured the new stuff in) but I will probably be buying some kind of precision applicators that I can refill soon.

As for the card itself, it ended up having at least 8 pins near the top left corner of the right-side TMU that were loose. Some across the top edge, some across the left edge. I'm guessing the card took a hit directly on the TMU at some point and it forced them loose. It took a little while to fix them but it wasn't as bad as I thought it'd be and it works flawlessly now. I kept fixing them and then testing the card until I got them all (there were visibly less artifacts each time I tested it). I think the flux was making them stick together a bit which made it harder to tell which ones were loose, and I was trying to solder as little as possible because it takes 10 times longer to get solder off of pins that have accidentally connected together. Flux seemed to help, but it was still a pain.

Any tips for preventing the bridging of pins on chips like these in the future? And what should I do to unbridge them? I know dragging across pins can be helpful to redistribute the solder, but I've had just as many bad experiences doing this on other chips. I've dragged UP the pins before to spread the solder as well, and that can work but sometimes you end up with a mess doing this too. One thing I'm extremely hesitant about is desoldering braid because I've had it stick completely to pins which leaves an amateur like me the choice of overheating the solder pads to get it off, or yanking it away too forcefully and destroying the pins AND the pads.

Fun stuff. 😆

Now for some blitting from the back buffer.

Reply 6 of 7, by sdz

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Glad to hear you fixed it!

Drag soldering works quite well with the right flux, right tip and the correct temperature. There are many types of flux out there, some are really good, some are crap.
Solder wick is really useful if the drag soldering approach doesn't work, same as the flux, some brands are real good, others are awful. I personally use Loctite branded solder wick and it's quite good.
If the braid gets stuck on a couple of pins, don't yank it away, just add some more solder 😀

Reply 7 of 7, by pentiumspeed

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I prefer flux paste AMTECH 559 flux make sure it is not from chinese. I had tried few different fluxes and came back to this. Cleans up nicely with alcohol.

Cheers,

Great Northern aka Canada.