So I was powering some crazy experimental apparatus and suffered an "event" that killed the Topward 6306D dual tracking power supply. I had a spy infiltrate the Topward service center in California and he obtained a schematic for "nearly" the right unit. Troubleshooting found several bad op-amps and voltage references on both the Master and Slave boards. Replaced those and now everything, all functions, are working fine again... EXCEPT that I can not turn the Master side down below 4 volts. The lowest it will go after considerable warmup time is 3.7 volts. All voltage settings, current limiting, tracking, parallel and series, meters, indicator lights, all of that is working fine. Only fault is the minimum voltage on the Master side, I should be able to turn it down to zero.
Any ideas? Unfortunately the "nearly right" schematic filesize is too large to upload. For some reason Topward schematics are hard to get hold of, at least for me (at least for free.)
(sorry I originally attached the wrong schematic and the nearly right one is too large to upload.)