Started going through the entire set checking resistors and replacing any out of tolerance. Finding a fair number of drifted ones, mostly higher resistance ones that have gone even higher.
Found a strange situation with R168 and R169 in the focus circuit. Both are 680 ohm, 1W, 10% carbon comps. Connected directly in parallel and located right next to each other. Appear to be identical manufacturer parts, both look fine visually. One reads spot on 680 ohm, one near 1K. Go figure...
