I have been having problems with the tuning capacitor drive. The moving vanes seem very heavy and tend to drop back under their own weight. The rear bearing on the tuning cap is not adjustable, it is a spring plate fitted over the ball bearings and secured with 2 screws.
I removed and tried to increase the tension in the brass strips which rub on the shaft to earth the moving vanes, this helped a little but the vanes still tend to drop sometimes.
It is not helped by the fact that somehow the housing and the bearing surface in the concentric slow motion drive has been damaged. There were cracks in the pressed steel cup which forms the outer face for the 2 ball bearings to engage on.
One of the problems I believe is the slow motion drive only used 2 ball bearings, most modern ones have 3 or 4 bearings, giving greater grip between shaft and outer bearing.
I have had several attempts to fashion some sort of repair on the small pressed steel cup. first was to reshape it and press the crack together, that did not work it just opened up again. Then I tried covering the crack with a large blob of solder to stop it opening,
that still left a slightly pitted surface inside the cup, so then I tried smoothing the inside bearing surface with solder to help to even out the cracks. But the pressure caused by the ball bearings rolling round the surface is too much for soft solder to take.
I have now tried it with a steel wire shaped into a circular ring and soldered all round the housing rim to strengthen and help stop the crack from opening again.
Using a small grindstone in a Dremel I have ground down the bearing surface to help smooth the edges of the cracks and even out the pitting. This seems to be working more reliably but the vanes still occasionally slip down a little.
I wonder if anyone has a spare tuning cap of the same type and could let me have a replacement bearing cup.
Mike
I removed and tried to increase the tension in the brass strips which rub on the shaft to earth the moving vanes, this helped a little but the vanes still tend to drop sometimes.
It is not helped by the fact that somehow the housing and the bearing surface in the concentric slow motion drive has been damaged. There were cracks in the pressed steel cup which forms the outer face for the 2 ball bearings to engage on.
One of the problems I believe is the slow motion drive only used 2 ball bearings, most modern ones have 3 or 4 bearings, giving greater grip between shaft and outer bearing.
I have had several attempts to fashion some sort of repair on the small pressed steel cup. first was to reshape it and press the crack together, that did not work it just opened up again. Then I tried covering the crack with a large blob of solder to stop it opening,
that still left a slightly pitted surface inside the cup, so then I tried smoothing the inside bearing surface with solder to help to even out the cracks. But the pressure caused by the ball bearings rolling round the surface is too much for soft solder to take.
I have now tried it with a steel wire shaped into a circular ring and soldered all round the housing rim to strengthen and help stop the crack from opening again.
Using a small grindstone in a Dremel I have ground down the bearing surface to help smooth the edges of the cracks and even out the pitting. This seems to be working more reliably but the vanes still occasionally slip down a little.
I wonder if anyone has a spare tuning cap of the same type and could let me have a replacement bearing cup.
Mike
