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Re: S3 Virge GX 385 Video Noise Recap?

Posted on 2019-06-06, 01:56

Taking a look at the design it has 3 internal power planes, one ground, one 3.3V, and one 5V. They seem to just strategically place caps at points around the board. However, this board had quite a few unpopulated capacitors. I think this was probably a cost savings measure and also that the board …

Re: S3 Virge GX 385 Video Noise Recap?

Posted on 2019-06-01, 20:58

Replaced all the electrolytics with new higher quality and it has improved the noise probably 70% or so. Interesting aside, they had all drifted higher, some 50%. I've read that is typical of using 16V caps on lower voltages. I really think it is on the power filtering side. I'm going to try to …

Re: S3 Virge GX 385 Video Noise Recap?

Posted on 2019-05-22, 03:36

I am a total newb with a scope, but below is a video of startup probing the 3.3V regulator output on the cheapo Virge board. Looks noisy (+/- 0.5V) and the scope output corresponds to the noise on the screen. 5V off the PSU looks fine (sine wave +/- 4%). Note, the grid lines are 0.5V. https://youtu. …

Re: S3 Virge GX 385 Video Noise Recap?

Posted on 2019-05-21, 02:18

So maybe we are on to something here... The STB board is completely 5V and the cheapo board is 5V/3.3V (presumably for 3.3V SGRAM). Could the linear voltage regulator be picking up some noise from other components? See pics of the STB board below, you can also see the inductor/capacitor pairs for …

Re: S3 Virge GX 385 Video Noise Recap?

Posted on 2019-05-19, 03:21

So I removed the SMD caps and inductors from the RGB lines. I then shorted where the inductors were. It's slightly better, but still get the shimmer/jitter. Especially when the CPU is loaded at high res (starting up a linux boot cd). Any idea where on my board are the equivalent pin 3+4, 12+13? Also …

Re: S3 Virge GX 385 Video Noise Recap?

Posted on 2019-05-18, 19:13

Sounds promising. I'm going to try to remove the inductors and capacitors on the output. I don't have an empty U3 pad, I do have a similar pad U15, but its populated with an IC (see pics). Before I go all medieval on it, here are some pictures of the cheapo Virge/GX with the jitter/shimmer issue. …

Re: S3 Virge GX 385 Video Noise Recap?

Posted on 2019-05-13, 15:53

I don't even know where to start ripping filters out. I'm not having any luck on google either. Are there some basic guides to how these things were designed? Is it a power filtering issue or just a analog video signal filtering issue? Is the DAC integrated into the silicon or is it external on the …

S3 Virge GX 385 Video Noise Recap?

Posted on 2019-05-12, 00:33

So my S3 Virge GX 385 (4MB SGRAM) PCI has always had some shimmering (best way to describe how the pixels move) video signal noise especially at higher VESA resolutions. I confirmed it's not any other issue because my Cirrus Logic 5434 board works fine with absolutely no noise in the same machine. I …

Re: Sierra/Dynamix sound driver hacking

Posted on 2019-01-17, 05:16

in DOS
Thanks, seems to be working better. Another question. I use 300H for my General Midi output. I have used the Sierra Midi Driver Port Changer from here: http://www.sierrahelp.com/Utilities/SoundUtilities.html This works fine on LSL6, GK. But, for TIM2, it does not seem to work. Any way to change the …

Re: SoftMPU project needs your help! (game & sound card testing)

Posted on 2019-01-12, 22:25

in SoftMPU
I only load SoftMPU when required. Any game that uses MT-32 (LSL3 (intelligent mode), Monkey Island (uart), etc). The RA-50 does not recognize "all notes off" command and SoftMPU fixes that, even for games that don't need intelligent mode. On boot, I don't load SoftMPU. It would be nice not to have …

Re: SoftMPU project needs your help! (game & sound card testing)

Posted on 2019-01-12, 15:41

in SoftMPU
I'm experiencing the following issue... 1. Load SoftMPU (ATC-6631 YMF-719E-S) /MPU:330 /SB:220 /IRQ:7 /RA50 (I have an RA50 and an X2) 2. Run a protected mode game like Doom (works fine with GM outputting to X2) 3. Run a real mode game like Monkey Island and there is no output on the MPU interface …

Re: Yamaha YMF71x SB Pro Mixer Bug Issue Fix

Posted on 2018-11-09, 02:57

Thanks for the info. I did notice that when changing CD input mixer volume that there were pops. So I went back to the drawing board and ended up keeping the 1k ohm in-line resistor and reduced the decoupling capacitor to 1uF. I also left out the 220 ohm resistor to ground because that was the …

Re: Yamaha YMF71x SB Pro Mixer Bug Issue Fix

Posted on 2018-11-08, 05:03

So ran into another issue on my ATC-6631. The CD Audio volume seemed really really low, even with the mixer setting at 7. I tried multiple drives, so that wasn't the issue. Looking at the input circuitry, there is a 1k ohm resistor in series and then there is a high pass filter with a 220 ohm …

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