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Beomaster 4400 Mains Hum

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fasterbyelan
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fasterbyelan posted on Mon, Jun 4 2018 11:28 AM

I bought a Beomaster 4400 last week and whilst pleased with its performance a slight amount of mains hum at switch on, which initially went as the unit warmed up, has now turned into something quite horrendous and I can no longer use the receiver.  The hum is present regardless of volume setting and input selection so I'm suspecting the unregulated power amp power supply has fail in some way.  Does this should sensible?

 

I ought to replace the two smoothing capacitor anyway given the units age (OC8 &9), is there any preference in part type?

 

Thank you for any help given.

 

 

Karl

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Peter
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Peter replied on Mon, Jun 4 2018 5:36 PM

Is it from the Beomaster or through the speakers? The transformers can delaminate  and hum badly - certainly do on the 3000 - short term fix is putting two halved squash balls under it and this reduces the noise! 

Peter

Beo_Jean
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Good point Peter!

Also try the LINEAR mode to see of the hum comes from the tone control or from the preamp or the output stage...

Dillen
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Dillen replied on Tue, Jun 5 2018 10:46 AM

Check the idle currents.
An overloaded power supply can easily cause hum.

Martin 

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