I’ve changed Q540 (2N3904). -22V is back on track.
B wasn’t triggering. Changed bad Q150 from a PN3565 (which I couldn’t find) to a BC546B, and the unit is back in business and working beautifully.
All it need now is a modern replacement display because mine is missing 3 segments.
If anyone knows of a good modern alternative, let me know. I tried to contact the person that made
a board for a DC508, but I didn’t get a reply.