Measuring A Capacitor

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?"

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.

Here's one possible scenario: As he is inserting the foil or whatever he uses to create the short, it comes into contact with the center pin an instant before coming into contact with the ground. Meanwhile, his body is in contact with the foil. The static electricity on his body (perhaps he's even just been walking on a carpet) discharges into the center pin, then is amplified by the 80db or thereabouts that the system gain is likely to be, from phono input to speaker output. That's a voltage gain of 10,000 times.

Not something I would want to risk doing on my system!

Regards,
-- Al

The buzzing noise is at 60Hz (my guess), and is pretty loud (volume dependent). I know it's there, so I get bothered by it's presence.

OK, I did the shorted IC exercise, and there was no hum. What does that tell me?

It says that the problem is not the preamp! It is outputting hum because hum is going into it. There are many threads at Audiogon on phono hum problems that you can search through. A few possible causes that come to mind:

-- Your power amplifier is too close to either the preamp or the turntable or the turntable cable.

-- Lack of good grounding between the turntable and the preamp (as you mentioned in your first post).

-- The phono cable being in close proximity to ac power cords, or to the power amp.

-- Ground loop issues between the preamp and other components, which become more apparent in phono mode than when other sources are selected because the signal levels are much lower for phono. Try disconnecting everything from the system except for the turntable, preamp, power amp, and speakers.

-- Try reversing the polarity of the ac plugs of each of those components, and/or floating them (using a cheater plug).

-- When the turntable is connected, is the hum present both when it is turning and when it is not? What kind of cartridge are you using? Grado's in particular often have a problem picking up hum from the turntable motor (when it is on), because they are unshielded. (It could be that the hum you hear when the turntable is connected is not the same hum that you heard when nothing was connected to the preamp inputs).

HTH,
-- Al