Beomaster 2400 radio hum

[jansjobe]

I am restoring/repairing a Bang&Olufsen Beomaster 2400.

After a minute or so, I get a hum from tuned station, no hum between stations. Hum is propably 50Hz.
I have recapped all electrolytes.

I suspect something wrong in the stereo decoder section. Could it be the IC itself?

Has anyone any ideas?

Best Regards,
Jan Sjöberg

[Mark-sf]

Do you get the hum when you turn off FM Stereo? How about any other inputs?

[jansjobe]

The hum is ONLY on FM radio.

At first the hum disappeared when switched to mono. Now it is still there, but slightly lower.

[jansjobe]

[sonavor]

If you unbolted the main PCB from the cabinet for the capacitor replacement, did you keep the FM tuner (metal box) secure?  If the metal box was free to move while you were working it is possible a shield wire became disconnected…introducing the hum.

-sonavor

[Dillen]

A bad rectifier D50 wouldn’t be a first.
Also, check the solder joints around the standby relay.

Martin

[jansjobe]

It was in fact the bridge rectifier!

Thanks everyone for your time and effort!

[Author]

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