First post, by Ozzuneoj
This is one of the weirdest issues I've come across. I picked up a YUAN JRS-3DS100 nvidia NV1 card in a scrap lot recently. A few caps were damaged (bent over), it is missing the backplate and one leg on the STG2000X chip was bent and touching another. I replaced the bent caps with low-esr equivalents and fixed the bent leg on the chip, but the card still exhibits a lot of graphical corruption in the BIOS and at the DOS prompt (haven't bothered with Windows yet). My normal method of diagnosing after this is to check for broken solder joints, which I did, and I found a couple but I fixed them and it was still happening. Next, I thought it might be memory related so I pulled the two socketed memory chips. The corruption went away but it still hangs or drops the VGA signal some times. I tried different memory chips and it made no difference to the corruption, so I checked again for bad solder joints and found none. I started just probing around the memory sockets with a stick (seriously) and it didn't do anything... but when I squeezed the chips\sockets with my fingers I noticed that the corruption changed and went away a little. Eventually I realized that it wasn't the pressure that was doing it, but it was me actually touching the solder points on the back of the memory sockets that was making all of the corruption go away. After doing this several times it actually went away completely with the memory installed, but small flashing\moving pixels would start to creep back in after a few seconds.
When I take the memory out of the system completely the corruption is gone completely but it still hangs from time to time, and drops the VGA signal when I try to load an application (like Paku Paku).
It seems very strange that touching the contacts actually mitigates the graphical corruption. This tells me the card likely isn't fried... but I don't know enough about electronics\electricity to understand what is going on here exactly. Something about capacitance? Or grounding? *shrug*
I thought maybe it was a grounding issue because it is missing the back plate (and the case my test system is in has a black powder coated interior), but when I touch something metal between the VGA port and a nearby screw on the case, it makes no difference to the visual corruption.
My next option is to replace all of the caps on the card since they don't appear to be of the highest quality and they are 23 years old now. If anyone has any other suggestions, let me know. I want to get this card working. 😀
Also, this would be a great time for us all to figure out a way to produce good quality custom back plates for cards with uncommon layouts. 😉
Now for some blitting from the back buffer.