Hi everybody!
Finally I've solved the problem. Here you are my little story:
When I received the nox power supply, I noticed that motherboard connector are not configurable to change 24 pin to 20 pin. So, I had to return it. Instead, I bought a MSI MAG A650BN 650W 80 Plus Bronze where it's possible to change to 20 pins atx connector. Well, with a new popwer supply, I solved the hdd problem, but the dithering problem not.
The next step was to do a recap. Before starting, I noticed that a capacitor was missing on the board. I weld it but the problem persisted. So, I replaced all the capacitors. With the new capacitors, the dithering was reduced considerably. You had to look very close to the screen. I measure ESR from old capacitors and it was very bad. It was good idea to replace them.
Looking some old post from here I read generally voodoo card have a bit of dithering because of its DACs and depending on the monitor you can see a little or not. I assumed that was normal then. Anyway I searched if it was something related with a voodoo card and my monitor, a dell 2007FP. In a post where people posted test results of their monitors, was mine and I read in low resolutions sometimes you needed to activate autoadjust option manually so you can look the resolution correctly. Usually this feature is automatic but for some reason in low resolutions, this feature doesn't activate. Ok, I test this on my dell monitor and the dithering dissappeared completely!!! The imagen now is very clean.
So, the summary or guide would be the following:
- Check if your monitor has an autoadjust feature and enable it. Maybe the main problem is here.
- If the problem persists, replace old electrolytic capacitors with new ones (Good quality brand like Rubycon, Vishay or Nichicon for example).
Other details like a good VGA cable is very important to avoid parasitic interferences or noise.
I hope my experience can help other mates.
Regards!!
