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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
licoricepizza OP
48 posts
 
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
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almarg
9,670 posts
 
Yes!

-- Al
herman
2,252 posts
 
Sorry I wasn't clear. I meant take one interconnect and plug it into the right channel input of the phono and the other end of that same wire into the left input.

If it were mine I would short the input with the system powered up. I can't imagine a scenario where shorting an input would cause noise on the output but I suppose it won't hurt to turn it off first.

Good luck
licoricepizza OP
48 posts
 
Well, I tried the suggestion clarified by Herman. Buzzing still present. Now, I am going to try shorting the interconnect, and see where that gets me...
herman
2,252 posts
 
What kind of hum/buzz are we talking about here? The kind that you have to put your ear to the speaker to hear or the kind that you walk into the room and say "whats that noise?"
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