HP 3478A power supply whine?

[mmagin]

Does anyone else have a high-pitched (but line frequency modulated) noise coming from their HP 3478A when turned on?  I listened around when I had it apart to change the battery, but I couldn't spot it.  I tried using a piece of plastic tubing as an improvised stethoscope, but couldn't narrow it down to a single component.  It's somewhere near the transformer though.

It still works perfectly and has a 5 year old calibration, but it annoys me a bit, having sensitive ears.

[bitseeker]

I haven't encountered this on a 3478A. However, it's not uncommon for transformers or capacitors to generate noise. It's probably the transformer, but also check for capacitors that aren't glued down or may have come loose. That multimeter has been around for a few decades.

I know what you mean about sensitive ears. CRT monitors were extremely annoying when they'd whine.

[mmagin]

Yeah, it's odd, since I thought it wasn't a switching power supply, but maybe I need to take another look at the schematic.

[bitseeker]

As far as I know, it's not a switching supply. Something may be loose from age, a failing component might be causing an oscillation, or some of the "hot snot" may no longer be adhering to the board or component.

[mmagin]

Well, it's a lovely mystery, I think it may be time for me to get one of these: http://www.mcmaster.com/#1024t28/=11hz6nz

[bitseeker]

The doctor is in!