It's later. Started walking through the alignment to discover that there's no TX audio. Noticed the ground for the compressor board looked corroded. Cut it and resoldered, no go.
Worst case it would be the SL1626C chip. So, of course, it was. Lucky for me the TRC-448 I never fixed the chopped out mode switch on has the same chip. Swapped it out, audio is restored.
I now have a working Sidebander V. And it seems to work very well.