I've been working on a GE 409 tube AM/FM receiver (circa 1954) - AM plays fine, and FM sounds good when a station is finally tuned in. Problem is that tuning on FM is erratic - have to rock the tuning dial back and forth before a station finally 'locks in'. No smooth tuning in and out of a station, like a properly operating FM radio. Have tuned the IF and discriminator, but did not help. Looking for troubleshooting ideas at this point. Thanks,
Craig S

After a lot of debugging, I found that the FM tuning cap's little press-fit brass tabs (that connect the rotor shaft to the sides of the cap) were dirty and not making good electrical connection. They were easy to lift out, clean, bend a little (for more tension), and replace. Made all the difference - now tunes FM fine.

-Craig S

:I've been working on a GE 409 tube AM/FM receiver (circa 1954) - AM plays fine, and FM sounds good when a station is finally tuned in. Problem is that tuning on FM is erratic - have to rock the tuning dial back and forth before a station finally 'locks in'. No smooth tuning in and out of a station, like a properly operating FM radio. Have tuned the IF and discriminator, but did not help. Looking for troubleshooting ideas at this point. Thanks,
:Craig S

This is a common problem, and I know I have made mention of that contact area (in some it is a coil spring) numerous times.

Another way to address it once cleaned is to apply a drop of "Rail Zip", it will keep it lubed, and reduce the chance for corrosion to develop again for quite some time.

:After a lot of debugging, I found that the FM tuning cap's little press-fit brass tabs (that connect the rotor shaft to the sides of the cap) were dirty and not making good electrical connection. They were easy to lift out, clean, bend a little (for more tension), and replace. Made all the difference - now tunes FM fine.
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:-Craig S
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::I've been working on a GE 409 tube AM/FM receiver (circa 1954) - AM plays fine, and FM sounds good when a station is finally tuned in. Problem is that tuning on FM is erratic - have to rock the tuning dial back and forth before a station finally 'locks in'. No smooth tuning in and out of a station, like a properly operating FM radio. Have tuned the IF and discriminator, but did not help. Looking for troubleshooting ideas at this point. Thanks,
::Craig S