Mic Pre Hums

[craigmorris74]

I've got a tube/solid state hybrid mic pre that has started to hum when I turn it on.  When I say hum, I mean I can hear hum coming from the box, not while I'm monitoring with phones or speakers. 

I don't remember hearing this before.  Is there something that would be an obvious place to check to see if something is wrong?  In input would be appreciated.

Craig

 

[desol]

Transformer?

 

[craigmorris74]

If it is the transformer, will the voltage coming out of it necessarily be off?

 

[desol]

No...the voltage will probably be ok. But there could be a problem with the laminations, which will cause it to hum.

 

[craigmorris74]

OK, thanks for your help.

 

[joaquins]

You should put wax or varnish to the PS transformer, the vibrations can make a short circuit in the windings, see for wax potting in the web.

JS

 

[pstamler]

You may need to schockmount the transformer too; rubber grommets can help.

Peace,
Paul

 

[craigmorris74]

I appreciate the tips guys.  I'll try these things out, and if not order a new power transformer.