utahraptor wrote on 2020-12-25, 19:25:

The sound card gets mixed through it and both channels work for game sounds. Is there some setting for balance?

My SC-88VL has a similar issue with one of the channels (left or right, I don't remember which) when using the line-out on the back. The headphone out works fine in stereo, however, so I use that (TRS 3.5mm to L/R RCA cables). I should look into fixing it .

What does "both channels work for game sounds" mean? Your sound card plays back speech normally, but audio from the SC is messed up?

If that's the case, I had an identical problem with a SC-55mkII many years back. I took it to an audio repair place (these days you can find them on Facebook and in audio/Roland groups in your area). He said the channel had been messed up from what seemed to be a fall, he got it working pretty quickly.

I mean that the output from my SB16 clone that is sent to the input of the SC-88 and then sent back to the line in on the SB-16 contains game sound effects for both the left and right channels. The MIDI sound coming in through the same cable however is only from the left speaker whereas the same midi music played by the SB-16 comes out of both speakers.

Cold/cracked solder most likely. A quick reflow will probably fix it.

Unrelated but the volume wheel on CM units are junk, can often short out a channel as they age.

Is there any kind of guide you could link me for solder points for the device?

Not really. If you don't have a tester, I'd just start with the jack itself. If a reflow there doesn't fix it, then you might just have to "shotgun" it and reflow all of them.
But if the headphone jack works, then the RCA jack itself would be my guess. It's also possible you just have too much corrosion in there as well.

roger that, will be kind of scary, but I will see what I can do this weekend