Fluke 3330B Calibrator buzzing noise

[Jim Narem]

I got a Fluke 3330B calibrator on ebay in unknown condition.  After
cleaning it up, it seems to work but it makes a buzzing noise when
in operate mode.  The frequency varies with output voltage which
probably means that the buzzing is related to the VCO that regulates
the HV transformer power output.  It buzzes slower under low loads
until it hits a certain point and the buzzing is a constant frequency.

I've checked the power supplies for ripple and they look OK.  I was
wondering if anyone else had used one of these and if the buzzing
was normal.  I have another HV power supply (an HP 6521A) which
has a big notice on the back that says "ticking sound normal" and it
makes a fairly disturbing noise from the pulse transformer as it
regulates the HV.

......jim (narem at narem dot com)

[Testtech]

Yes, these do buzz a bit.. When ever I have repaired any of the Fluke calibrators, the first thing I do is really carefully check all the aluminum electrolytic caps. Most of the small ones will need to be replaced. Also check for overheated carbon comp resistors, a common problem with these. Relays can also be a headache. 

[dacman]

I maintain a 3330B, and it doesn't buzz at all.  Pull the cards and clean the contacts (with DeoxIT).  As stated, the little electrolytic capacitors do go bad.  If you have a Variac (with a current meter), measure the current draw and make sure someone didn't put in a high value fuse.

[pelule]

My 3330B started one time in the past also buzzering at the highes voltages.
It was cause by the pre-regulator board. Thus I would check the e-cap at this board first.
Now mine is quite again.