[EdHolland]

I poked around a little more, and found the folded dipole that I've been keeping for no apparent reason. FM comes in pretty well across the dial in mono, but I am sure would benefit from alignment.

Selecting Stereo, or FM automatic indicates that there is some issue here. On "Stereo" the relay clicks (switching the MPX module I think) but the signal is cut out. On "FM Auto", careful tuning on strong signals will cause the relay to activate.. and the sound to cut out. It seems to me that there is an issue somewhere in the MPX circuitry, but that it might be detecting that a stereo signal is present - enough to switch the signal path.

More fun detective work

EDIT: Progress!

Had a few minutes to look things over. I checked, and very carefully cleaned the relay contacts, using a piece of clean card, on to which a little De-Oxit was applied. Proper connections re-established. Also checked the bulb in the stereo indicator - and it was open circuit. I exchanged it temporarily for the bulb behind the signal meter. A new set is in order all round, as the tuning dial lamps are not working either.

On a re-test, I found that V101 in the multiplex section was not heating. I jiggled it, and then got one stereo channel - Good, not a dead tube. Pulled all the small valves and cleaned the pins. Success! Working stereo. In fixed "stereo" mode, it seems to demultiplex on all channels, but tends to sound a bit scratchy, hissy and distorted, which could be my dodgy basement signal or alignment. The "Auto Stereo" will click in on some stations, but even on strong signals, seems a bit reluctant and is very picky about tuning.

I need to think about alignment, as I don't have much gear for this. First thing is to read the procedure thoroughly.