Hi Stephen,
My first thought is that the series regulators on +/-10 are not regulating.
Most obvious issue would be Q213 and Q217 are shorted, and/or D213 and D216 are open.
Check the 27VAC at the transformer, and verify that you see about 14VAC between each side and Ground.
Given all the problems you already found and fixed, perhaps the unit was exposed to a "catastrophic" event, such as being powered by 230V when the switch was set to 115V.
Pete
saipan59 (Pete)