Replaced U22. Works perfectly now.

Thank you both for your extremely valuable help.

I am pretty surprised that this issue is not discussed in detail anywhere else, since even I myself have a second model with exactly the same problem. So it seems to be fairly common.

I found a handful of forum threads describing a similar or the same defect, but there never was a solution. If anyone has a similar issue, drop me a pm, I do have 8 spare opamps 😀

Below is the new opamp in place, please excuse the bad soldering job especially for R62, as well as the flux residues. Everything will be nice and clean, but I still need to replace the line-in jack 😀

A LOT easier for U19 on the CT2290. Also fixed the issues completely.

Awesome, congratulations ~

This has been a good read. Great work!

It wasn't over... This card is like a super-villain, who jump-scares you after you think, you've definitely beaten him.

Turns out the WT header wasnt working and I was getting garbled sound or none at all.

Again, the DC voltage on the opamp closest to the WT-header (U10) was inconsistent (0.8 V on one output, 2.5 on all others). I wasn't able to probe the signal, since the PC kept crashing almost instantly, when playing back anything via port 330 (with or without WT board). I also ran SBMPU401, no effect.

So, I went ahead and removed U10 and discovered a big blue mess. This doesn't look like your regular greenish oxide and I have no idea, if it came from the chip itself. But I also saw similar deposits below two of the caps, I previously removed (not located next to the chip and the caps tested fine). There is also a little bit visible under the DC-converter P3, but I will certainly not touch that.

Anyway, with another opamp replaced, now, finally, the card is fully functional, including the MPU-401 interface and WT header.

The End

Well I recently got my hands on a a ct1740 , I want to use it because its jumpered and seems to work without conflicts unlike my ct2230 and sure enough the left channel is totally dead.

Would it be possible to remove the chip with a regular soldering iron , or would I need to use a hot air gun?

AppleSauce wrote on 2022-12-03, 07:37:

Would it be possible to remove the chip with a regular soldering iron , or would I need to use a hot air gun?

It is possible, but definitely harder: https://youtu.be/NrB1Rdrglng?t=50

Well I'm game to give it a go , would this chip be a suitable replacement?

I ended up getting a hot air station , and the chips, but looking at the data sheets there seems to be some differences.
So I'm not sure whether I can get away with using the ON semiconductor 3303s or if id need to use the SGS/ST 3303 chips.

The opamps are same on the most important parameters so there is no need to seek out specific brand.

Tiido wrote on 2023-01-01, 14:00:

The opamps are same on the most important parameters so there is no need to seek out specific brand.

Awesome thanks for letting me know , sometime this week I'll try and fix the card and let you all know how it goes.

Well I replaced the chip , I needed to remove the caps next to it to get to it , and I melted the volume wheel a bit somehow.

It hasn't fixed the issue though, id say its made it worse now , in the duke3d sound test everything sounds crackly and distorted and the left sound channel still seems weak. I hope I didn't ruin the rest of the card.

Then there's a good chance there are other bad opamps too and perhaps a few bad capacitors here and there too.

Tiido wrote on 2023-01-04, 10:42:

Then there's a good chance there are other bad opamps too and perhaps a few bad capacitors here and there too.

I thought each op amp did one sound chanel though?

There are a number of functions spread across all 4 chips and their total of 16x individual opamps, i.e U10 has CD and possibly WB header related functions, U11 does OPL3 related things and something for the SB DAC+ADC chip.
I don't have a card at hand to take closer looks, I know I have two of these cards in storage somewhere (I moved to another country 2.5 months ago, some things are still not accessible).

You can put some music playing and use a line-in of another device to poke the sound path, listen opamp input and output pins and perhaps identify one that misbehaves this way. That is how I identified such issues before I got an oscilloscope. (but be sure to connect up ground first to somewhere and avoid any shorting of neighboring pins).

Tiido wrote on 2023-01-04, 12:53:

There are a number of functions spread across all 4 chips and their total of 16x individual opamps, i.e U10 has CD and possibly WB header related functions, U11 does OPL3 related things and something for the SB DAC+ADC chip.
I don't have a card at hand to take closer looks, I know I have two of these cards in storage somewhere (I moved to another country 2.5 months ago, some things are still not accessible).

You can put some music playing and use a line-in of another device to poke the sound path, listen opamp input and output pins and perhaps identify one that misbehaves this way. That is how I identified such issues before I got an oscilloscope. (but be sure to connect up ground first to somewhere and avoid any shorting of neighboring pins).

Right but U22 would handle the left channel?

Probably both left and right of some certain function, it doesn't seem any of the chips do just one channel. Most of the parts around the chips are symmetric, showing that both channels go through them and are processed equally.