This board sounds very close to Roland SC55 and all the later Dream/Crystal things with the GS soundbank. Without being intimately familiar with them all it is hard to hear a difference.

A WB card gets MPU401 signal from the host card and outputs analog audio back that goes to some mixer input on the host card. Make sure you have not muted the releveant input. On Creative cards it should be same as the FM level, but since you mention cracking noises then it is unlikely this is the problem and the WB card itself is at fault.

Can you show photos of both sides of the board ?

I had another test today using totally different setup with Terratec Base-1 which (I believe) should have no compatibility issues. Result was the same, no audio, just nothing, in both Windows 98 & DOS.
North of CS9233 is located CS4331-KS DAC from where analog output is buffered using 064 OP-amp located NE corner. If I can build some kind of test bench I'll measure supply voltages and then scope input and output of the DAC. If there is some data I might have a change, this is getting interesting...

Nothing looks visually wrong. There is a good chance the 4 black capacitors are dead. I have had to replace these on one card I worked on to get sound output (but it did have one, just really really quiet).

If you can wait a few months I can take a stab at repairing this card (if capacitor change won't help), I'm in the process of moving to Norway right now (less than 2 weeks until the transportation aspect begins) and do not have a workspace anymore.

Whats your setup, any other cards in your system?
Do you have any other wavetable cards to test your setup with?

Current setup is GA-586TX with Terratec Base-1 + some random ethernet and Matrox G200. I don't have any other wavetable cards, this is actually my first one. Thats why I'm fishing for configuration hints. Now I use Windows 98 MIDI player and I have changed MIDI playback=Roland MPU401 from multimedia settings in control panel. Everything plays fine when MIDI device= default internal "Yamaha OPL3/FM", but not with the wavetable.

Today measured the board and found some cracked solder joints from TH regulators etc. Re-soldering those did nothing special. Also measured signals with oscilloscope. Saw nothing from the digital and analog outputs. Supply voltage is a bit low, about 4,7V. CS9233 datasheet recommended is above 4,75V. I don't believe it's too low but I have to check it. UART data comes alive when midi file is played. Also "something" happens in RESET/ line, need to verify that better because there was like some kind of interference/signal. Seems like nothing happens around the CS9233.

I'd drop unisound for now and go back to a default creative driver setup first, to rule out any driver errors. And run everything in msdos.

So; (autoexec.bat)
SET SOUND=C:\DRIVERS\SB16
SET BLASTER=A220 I5 D1 H5 P330 T6
C:\DRIVERS\SB16\DIAGNOSE /S
C:\DRIVERS\SB16\MIXERSET /P

(config.sys)
DEVICE=C:\DRIVERS\SB16\DRV\CTSB16.SYS /UNIT=1 /BLASTER=A:220
DEVICE=C:\DRIVERS\SB16\DRV\CTMMSYS.SYS

(You might need CTCM/CTCU aswell as youre using a pnp card)

Then any game should detect the wavetable card on 330. (or 300 if you set it to that)
Also pull any cards you dont need for now, it is possible they hog the resource for it and it just wont work outputting weird noise, especially if youre using other mpu-401 cards.

I had that kind of setup and basically it didn't work with CT2910 at all. FM was missing. I've read someone other here had the same issue... I have tried Terratec DOS driver without unisound.

Anyway, soldered off EPROM (MX27C1000) just to dump it and see what's there, but all I can read is FF FF FF...whole thing. Chip ID is also read as FF FF. I can read other chips like similar MX27C1000 (DIL32) without issues. If the EPROM was dead, I believe host synth chip CS9233 would act just like this, because it contains firmware for internal MCU. Without any firmware probably nothing happens. Let's see if someone has dumped Crystal EPROM HEX somewhere, I assume it's the same for wavetable cards with two ROM chips.

That sounds like it never worked in the first place... Or the OTP EPROM died somehow along the way.

I have few dumps and each ROM arrangement has its own firmware that is incompatible with others. (send me a PM)