DuMont Inductuners

[Electronic M]

Originally Posted by bigaudioal

Thanks for these suggestions. What parts are the sliders you are talking about?

They are little copper pieces that connect between the metal on the white ceramic and the coil wound on the brown phenolic. Their arms grab the coil and as the coil turns they slide along the ceramic. You may want to bend the arms closer together so they grab better....Also look for vertical motion in the shaft. If the shaft bearings are missing or miss-installed or the back pressure pivot screw for the shaft is too loose excessive vertical (or perhaps horizontal) slop may be making the sliders hop out. One coil is reverse wound so it's slider will move opposite the others. You will want to clean the coils and all metal surfaces with Goof-off there was some nasty dirty greasy residue on the tuner in my RA-103 that nothing else was getting (and I could not see it till it came off).

EDIT: Another thing you may want to do is sawp in as many different 6J6 tubes for the osc. as you can. Tube testers only tell you the emission/mutual conductance, and NOT how well it will oscillate in a given osc. circuit....A strong tube may suck at oscillating, but a weak one may do it like a champ.