[NJARC] Hi, Guys. What am I looking at here?

[Aaron Hunter]

Dave

Did you try turning the plug over if it is not a polarized plug? 

I've had 50C5s give me hum problems, try another one. 

Make sure the connections at the cartridge are tight and wires properly 
soldered and not broken. The leads can act as an antenna. 

Short the leads at the cartridge to make sure the cartridge itself is 
not causing some kind of noise.

Aaron

Dave Sica wrote:
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> _________________________________________________________
> Virtual repair clinic anyone?
>
> You may recall my post a few weeks ago about "Looking for a phonograph
> for a young person" or something to that effect. I spent today working on
> the record player I picked up from Darrin Hoffman at the club meeting
> yesterday. He had done a wonderful electrical and mechanical
> refurbishment and the thing plays like the day it was new. The girl we're
> giving it to is coming over tomorrow to pick it up (she spent today at
> the Princeton Record Exchange stocking up!) and I spent today sprucing up
> the cosmetics.. (I hadn't ever "restored" a set with that
> leatherette/painted paper covering and it was a learning experience!) It
> now looks like 999,000 bucks. (I would have said it looked like a
> million, but to be honest, there are at least a million paint speckles I
> didn't deal with. The future owner probably has more patience than me
> anyway.)
>
> Anyway, here's my predicament. After running this thing off and on all
> day and marveling at how nice it sounds, late this evening it apparently
> decided to get noisy.  There was always a bit of hum, about what you'd
> expect from the 35W4-powered 50C5 amp.  But now it's got more hum, I'd
> say a fair amount of hum. Maybe still acceptable. Possibly even still the
> same as it was this morning except that now I'm paying attention. What
> caught my attention was a new noise, a buzz. Sounds a lot like
> interference from a fluorescent light, but it only appeared at night and
> I've got most of the lights in the house turned off. Even stranger, the
> buzz is most noticeable when the volume control is down, GOES AWAY (!?!)
> when you advance the volume control slightly and then RETURNS and
> strengthens (along with the hum being amplified) as you advance the
> volume control further. I don't recall ever hearing about that type of
> symptom before.
>
> I'm the farthest thing from a competent electronics engineer, but I can't
> imagine this high frequencly damped wave buzz is coming from inside the
> record player. But then again, I can't figure out where it might be
> coming from. Or why it behaves the way it does when I fiddle with the
> volume control And why only now after it's been running for a while?  
>
> I've posted photos of the noise as seen on my scope at
> www.njarc.org/phono_noise. Can anybody figure out what's going on here?
>
> Thanks,
> --Dave Sica
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