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Hi all,

I'm working on an old Sonar FS-23. I have the TX and RX working very nice. There is a hum that comes from the speaker when the volume is turned down, it's pretty loud. Once you turn the volume up and hear static/signals it somewhat drowns the hum out.

The hum is very prominent in the TX audio as well. I have replaced all of the electrolytic capacitors in this radio already.

Someone suggested a loose power supply transformer, tried pushing down on the big black transformer in the back while the radio on and I was observing the rx hum, no change. All the transformers seem pretty well bolted down.

I'm also using tested/good tubes.

Any ideas?

[QUOTE="479tx, post: 334123, member: 22199"] Hi all, I'm working on an old Sonar FS-23. I have the TX and RX working very nice. There is a hum that comes from the speaker when the volume is turned down, it's pretty loud. Once you turn the volume up and hear static/signals it somewhat drowns the hum out. The hum is very prominent in the TX audio as well. I have replaced all of the electrolytic capacitors in this radio already. Someone suggested a loose power supply transformer, tried pushing down on the big black transformer in the back while the radio on and I was observing the rx hum, no change. All the transformers seem pretty well bolted down. I'm also using tested/good tubes. Any ideas? [/QUOTE]

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