Measuring A Capacitor


I have a preamp (NAD 1155) that has a hum problem. It started when I got a new turntable, so I thought it was a TT grounding problem. But no... The preamp's phono section hums every time it is selected. Even if there is no phono present. All the other inputs are dead quiet.

Anyway, a fellow 'goner thought it is a capacitor that's going 'round the bend. I'm willing to take my volt/ohm meter, and find the offending component, and replace it. All I know about capacitors is that they are measured in picofarads, and they discharge their energy in bursts, when it's requested.

Any help in this regard is much appreciated. I have a mountain of vinyl waiting to be played.

TIA

Lee
licoricepizza
I would first try taking a single interconnect and connect one input to the other. That might be enough to shield the input and if the hum stops you know it is coming from outside. If it still hums no need to sacrifice anything. Plug an interconnect into each input and on the other end gently jam something between the center pin and the outside ring to short them, piece of aluminum foil would work.
The IC to every input didn't work, so now I'm on to shorting the ICs. We'll see... Do I need to turn anything off while I'm doing this? I'd hate to damage my Vandersteens while performing this. Also, I have a question. Someone thought a cap is going bad, hence the buzzing. If a component like that is bad, shouldn't the buzzing be present constantly? For me, there are times when the buzzing is totally absent.
Do I need to turn anything off while I'm doing this?

Yes, definitely, although it might be less critical if a different input were selected while you applied or removed the short. But that would be bad practice anyway.

If a component like that is bad, shouldn't the buzzing be present constantly?

Probably, but not necessarily. The component could be marginal or intermittent.

Regards,
-- Al
In order to be perfectly clear, I:

Turn the stereo off
Put the shorted IC in place
Make sure Phono is selected as the input
Turn the stereo back on
Turn my house into a smoldering pile ashes (just kidding)
Listen for the dreaded hum on the phono input

Thanks for all your help.

Lee