49-906 FM hum - Printable Version

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+--- Thread: 49-906 FM hum (/showthread.php?tid=7215)

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49-906 FM hum - Eric Adams - 08-11-2013

I just finished my 49-906. Replaced all caps, out of range resistors and a few tubes. Alignment was done also.
AM is good and strong-no hum. FM picks up a few stations but has a hum all across the dial. It does almost go away when tuned to a station.
What did I miss?

http://www.nostalgiaair.org/PagesByModel/675/M0013675.pdf

Thanks,

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RE: 49-906 FM hum - Mondial - 08-11-2013

You might try changing the 14F8 converter tube. If it has heater to cathode leakage, then the AC voltage for the filament will FM modulate the oscillator, causing a hum. It could also be the 19T8 tube, since different diode sections are used for FM.

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RE: 49-906 FM hum - Eric Adams - 08-11-2013

Thanks, I'll try a swap and let you know.

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RE: 49-906 FM hum - Eric Adams - 08-11-2013

That did it! The 19T8 made a difference.

Thanks, Mondail,

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