04-18-2013, 02:18 PM
Yes, I would try changing the 77 mixer/osc tube first. The autodyne converter is sometimes finicky as to tubes. The other thing you might check is the 77's cathode resistor (#8 on schematic) which should be 8K. If this resistor has drifted up in value, it can cause intermittent oscillation, especially at the higher freqs.