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Media Vision Pro Audio Spectrum Plus issue.

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First post, by Ozzuneoj

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I picked up one of these rather rare cards recently and decided to finally try testing it out today. I know this is a very old card, but when I pop it into my Windows 98SE test system (440BX, tried a PIII 850Mhz and PII 266Mhz) it is detected easily as a PAS Plus by the non-PNP hardware detection wizard and it installs without any problems or resource conflicts. I am getting normal audio from the left channel but the right channel just gives loud clicks and pops some times, but never any audio. Both FM playback and digital sound work on the left channel but not on the right.

It pops once as Windows is starting (but before the startup sound plays) and I get pops from the right channel when I try to adjust the volume with the volume slider in Windows. And it isn't just from the "ding" sound playing. It gives me repeated pops as I move the volume slider (click and drag). Is this some kind of issue with the right channel of the card's mixer being initialized?

Since the card is from 1992 and it only has FOUR electrolytic caps, I did something I don't normally do with sound cards and replaced them. It didn't fix the problem. There may be less noise on the working channel now, but it sounded pretty decent to me before. It's possible that one of the tantalums has gone bad, but none seem to be shorted. Maybe one has failed open? I know this can be hard to test without removing components. Anyone have any recommendations?

Is it possible that it is a speed sensitivity issue? I'm still in the process of putting together a 486-class test system (poor selection of AT towers), so it'd have to wait if that is the case. I noticed no difference between a PII 266 and a P3 850.

Also, my system has a power supply adapter that gives -5v, though I believe this may be one of the few PAS cards that supplies its own and doesn't require it from the power supply.

Other troubleshooting steps I've tried:
Reflowed nearly all of the through-hole components.
Checked the MVD101 chip for loose or bent legs
Checked for loose jumpers

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Last edited by Ozzuneoj on 2020-04-14, 04:37. Edited 1 time in total.

Now for some blitting from the back buffer.

Reply 1 of 7, by cyclone3d

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Try it in a slower computer.

The no FM is classic "computer is too fast".. or rather.. "ISA bus is passing commands to the card too fast for it to handle" symptoms.

Yamaha modified setupds and drivers
Yamaha XG repository
YMF7x4 Guide
Aopen AW744L II SB-LINK

Reply 2 of 7, by Ozzuneoj

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cyclone3d wrote on 2020-04-14, 03:57:

Try it in a slower computer.

The no FM is classic "computer is too fast".. or rather.. "ISA bus is passing commands to the card too fast for it to handle" symptoms.

I get digital audio and FM from the left channel perfectly fine. Are there speed related issues that only show themselves on one channel?

Now for some blitting from the back buffer.

Reply 3 of 7, by cyclone3d

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It kinda sounds like something else is messed up since one channel is working fine.. but who knows.

What are the ports on the card? Does it have a Line Out? If you try that and get sound from both channels then you know it has something to do with the amplified output.

Yamaha modified setupds and drivers
Yamaha XG repository
YMF7x4 Guide
Aopen AW744L II SB-LINK

Reply 4 of 7, by Ozzuneoj

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cyclone3d wrote on 2020-04-14, 05:33:

It kinda sounds like something else is messed up since one channel is working fine.. but who knows.

What are the ports on the card? Does it have a Line Out? If you try that and get sound from both channels then you know it has something to do with the amplified output.

Sadly it only has "MIC", "OUT" and "IN".

The last time I had a problem similar to this it was on a really beat up old GUS Classic. It turned out to be a damaged jumper. Doesn't seem like it's that easy this time though.

Now for some blitting from the back buffer.

Reply 6 of 7, by Ozzuneoj

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derSammler wrote on 2020-04-14, 06:46:

I think the jumper block between the two big caps changes between speaker out and line out, with the later one not using the amps.

Thanks for the suggestion.

I just checked it and it looks like these are used to disconnect those channels entirely.

Here's a rough idea of the pinout. I'm not that good with understanding circuits so I won't try to interpret this in too much detail. I just checked continuity with a stereo jack to stereo RCA Y-cable and wrote down my findings (for the Line In I had to check on the other side of a couple of resistors near the IN jack). I'm not exactly sure what the one pin is connected to (?).

The "MIC\IN" side of the jumper block had no effect on the sound output. The OUT side of the block seems to just disconnect each speaker. I'm sure to someone who understands circuits like this it makes sense. I took all the jumpers off and without a jumper across the R +/- pins I get no right channel sound OR popping. Without a jumper across the L +/- pins I get no left channel sound. What is this jumper doing exactly? How does connecting the positive and negative of an output signal make it work? Is it somehow different when the card is actually running?

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Now for some blitting from the back buffer.

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