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

[John Ruccolo]

Hi Dave,

I have several suggestions:

1) Tell the young lady to forget it and buy an Ipod! (like everyone else her age)
Just kidding....

2) Does the behavior change when you reverse the AC line plug? That's an old trick with anything that's AC/DC powered (or "transformerless").

3) It may be that the volume control just needs more cleaning. Give it a spritz of cleaner (like the stuff that John T. had at the meeting that I forgot to buy a can or two of) and work it back and forth.

4) Is there a preamp stage (like a 12AV6 or something) before the 50C5? 
I might suspect that area, or maybe:

5) Possibly the cartridge wiring? But I'm sure Darrin chacked all that....

6) Try swapping out each tube one-at-a-time -- I wonder if you could have heater/cathode leakage somewhere? If there was a H/K *short*, however, I would expect a LOT more HUMMM.

Just throwing some ideas out. Trying to fix things via email can be tough. ;-)

As a vinyl collector for over 30 years, are you telling me now I have to compete with people MUCH LESS than half my age? Sigh....no wonder I'm not finding anything at the local second-hand store.


Later,

JR

--- On Sun, 3/15/09, Dave Sica <davesica at juno.com> wrote:

> From: Dave Sica <davesica at juno.com>
> Subject: [NJARC] Hi, Guys. What am I looking at here?
> To: njarc at mailman.qth.net
> Date: Sunday, March 15, 2009, 12:53 AM
> Just remember 
> Reply = Poster
> Reply All = Everyone
> 
> _________________________________________________________
> 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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