I repaired one of these not too long ago, the video I made might help.
My unit had drifting carbon composite resistors that were replaced, the usual sticky switches that were disassembled, cleaned, DeOxit-ised and relubricated (the gold wafer cam switches were only cleaned with alcohol and paper as mentioned earlier in this thread), and a faulty LD110 (faulty as it warmed up) that was successfully replaced with an eBay sourced part.
Jared Cabot