Greetings folks! My first post here..

I am restoring a Pentium MMX 200 / 430TX system; and i'm having problems with my SB AWE32 and trying to determine if it's hardware or software. Model CT3910.

System is running MS-DOS 7.1/WIN98 SE. I'm using IDE (4GB CF) and the onboard USB ports for mouse/storage. System is running on an old (but physically clean) 230W AT PSU.

Using DIAGNOSE.EXE during a DOS boot or under Windows, FM sound and AWE32 "advanced effects" music *always* works, and sound clear.
However, The 8-bit and 16-bit digital sound either doesn't work at all; very rarely plays clearly for a few seconds, plays but is very garbled, and/or emits a bunch of static/noise only.

If I have a very noisy sound output that hangs around (such as after booting up Win98), once I open a DOS window and run diagnose.exe, immediately after selecting the first base setting (220H I think), the noise cuts out. Then of course forwarding to the output options, above is what still happens.

I've tried:
- PNP-Aware OS to NO in BIOS
- Disabled power management
- RAM test a few times in DIAGNOSE.EXE = pass
- DIAGNOSE.EXE: Tried various DMA/IRQ settings; no high DMA, yes high DMA, IRQ 2, 5, 7, 10, DMA 1, 3, 5, etc.
- Removed the PCI NIC -- so the only cards are video (ATI Mach64) and the Soundblaster. Maybe placebo seemed to help a little with making digital sound work a little more.
- Used Phil's Computer labs updated win95/98 drivers
- Tried different DIAGNOSE.EXEs -- both SB16 versions and SBAWE32 found on Vogons Driver repository.
- Headphone jack vs. Line out jack - no difference, just headphone is louder/too loud for my line in on stereo
- Warcraft 2 Battle.Net edition -- the digital sounds (i.e. Orc chopping wood) always works, but the music either doesn't work at all, or plays noise-ily as per above. The game runs OK - I don't see any weird system hanging going on.
- Reinstalled Sound drivers in Windows a few times
- REM'd the SET BLASTER stuff in Autoexec.bat
- I cannot switch it to another ISA slot as both slots would interfere with the processor. (unless I run the MMX without a heatsink, maybe I underclock to 2/2.5x50 MHz and try that?..)
- Manually set IRQ 5 / DMA 1 / DMA 5 to "Legacy/PNP" in the BIOS and set the card to match; no change
- The BIOS has a early 1998 date, have thought about updating but haven't tried it yet.

I don't think it's the cable given the FM and AWE32 output is consistent, clean, and will work for several minutes.

The card does have a layer of old dust on it, so I think my next step might be to get a good brush and try to clean it thoroughly with rubbing alcohol. I've at least briefly inspected the capacitors and I don't see anything leaking. I only have another untested SB Vibra 16S but that appears to have some damage from a cap that appears to be missing. I do not easily have another ISA bus system to try this card on. I also do not have another PCI video card handy to swap in.

Other Thoughts? Is the digital sound run through a specific portion of the card or chips I should more carefully examine?