Good. […]
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zuldan wrote on 2025-06-01, 06:29:
Modifying the BIOS (and confirming with Z-GPU and Everest), I reverted the cards memory back to 650MHz (from 350MHz) and Windows XP booted up perfectly in 800x600. I then changed the GPU back to 300MHz (from 250MHz) and the video loss problem returned, I couldn't boot into Windows XP. I was able to go into VGA mode (640x480) and get to the desktop.
Now that I have the schematics, I'm going to order caps from Mouser closer to the actual specs. If the capacitors were causing the problem, which ones do you suggest I replace first?
Only just got my oscilloscope. It's a cheapo FNIRSI 1014D. I need to figure out if it has the capability to do what you're asking 😉
Good.
If you are considering changing caps, go with anything around NVVDD, as this is the GPU core voltage. Meaning C1302 and C1304 on the output side of things. Input would be C1264 and C1267.
C1302: 510µF - 4V - 14mOhms ESR - 4.08A Ripple current rating
C1304: 510µF - 4V - 14mOhms ESR - 4.08A Ripple current rating
C1264: 510µF - 4V - 14mOhms ESR - 4.08A Ripple current rating
C1267: 510µF - 4V - 14mOhms ESR - 4.08A Ripple current rating
There are alternate variants as well, which appear to be used on the input side of your card:
470µF - 6.3V - 25mOhms ESR - 2.09A Ripple current rating
On the input side there's also C1371, which is more of a general bulk capacitor and not as critical for the switcher as the other ones.
C1371: 1000µF - 6.3V - 170mOhm ESR - 0.45A Ripple current rating.
Just from a quick look your scope might actually be able to do some basic analysis. If you do so, don't do it "free hand", ideally solder some test point to the PCB that you can remove later, where you can attach the probe securely to. That prevents shorting something out by accident.
myne wrote on 2025-06-01, 06:32:
Again, it can just as easily be the mosfets or drivers.
In all seriousness, give it a wash.
Yes. Wash. In the sink.
I agree with the cleaning, that's always part one. However make sure to have it properly dried and any residue removed.
Flaky FETs or drivers haven't come around for me a lot the last years, so they wouldn't be my first concern.
Again, without tracing the GPU voltage in time of error, it's hard to say if it's even the issue, same for caps.
zuldan wrote on 2025-06-01, 06:43:A small update....GPU at 250Mhz and memory at 650MHz works for a minute or so but then the no signal problem returns. So, it app […]
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A small update....GPU at 250Mhz and memory at 650MHz works for a minute or so but then the no signal problem returns. So, it appears reducing the memory speed is also required to make it stable.
Just to recap...
- GPU 300, Memory 650 = Cannot boot into Windows XP at 800x600
- GPU 250, Memory 650 = Can boot into Windows XP at 800x600 but after a while video signal is lost
- GPU 250, Memory 350 = Can boot into Windows XP at 800x600
* In all situations, as soon as DirectX is initialized (EG 3dMark or Quake 3 is run), I get video signal loss.
Interesting. Especially that it is a "time related issue". Does the time vary between "runs" and "no signal" with memory at normal clock, if you perform many 2D draw actions? Like opening files, refreshing the desktop etc?
If the timing is fairly consistent and unrelated to that, it doesn't sound to me like it is "traffic" induced, but could be environmental.
Are you able to apply heat or cold (like serious heat ~100°C or -20°C cold) to certain components to see if it has an influence?
For starters going with the easiest: Extreme airflow on both sides of the card to see if that prolongs the "happy phase".
Cheers!
EDIT: In general, you scope should be good enough to have a simple look at ripple on NVVDD, that gives a good indication how "stable" everything is. You can find NVVDD at TP25 if you want to add a test-pin.
