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

[John Ruccolo]

Dave,

I emphasized heater/cathode *leakage*, not necessarily a short. If there was a short, you would have very high hum levels (it would sound like bad filter caps). 

One possible clue to H/K leakage was that the hum worsened as the day went on.

50C5's and 35W4's are prone to the H/K leakage problem. Try swapping each one out, AND the 12AV6 as well.

I just don't get the behavior of the volume control....

All kidding aside, I think it's great that young people are interested in stuff like this.


JR

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

> From: Dave Sica <davesica at juno.com>
> Subject: Re: [NJARC] Hi, Guys. What am I looking at here?
> To: njarc at mailman.qth.net
> Date: Sunday, March 15, 2009, 12:41 PM
> Just remember 
> Reply = Poster
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> _________________________________________________________
> 
> On Sun, 15 Mar 2009 07:27:19 -0700 (PDT) John Ruccolo
> <jr6v6gt at yahoo.com>
> writes:
> 
> Thanks for the suggestions, all.  I'm looking into it
> but haven't nailed
> anything down yet. Anyone with any other ideas while I'm at
> it?
> 
> > 1) Tell the young lady to forget it and buy an Ipod!
> (like everyone 
> > else her age)
> 
> I had suggested that she get one of those USB turntables so
> she could
> play the 78s into her iPod. She made it clear that actually
> spinning the
> scratchy vinyl (or in her case it's the shellac she likes)
> was the
> experience she was looking for. 
> Aren't you just charmed by that?
> 
> > 2) Does the behavior change when you reverse the AC
> line plug? 
> 
> That's the first thing I tried, along with shutting off all
> the
> fluorescent lights and dimmers. No luck there.
> 
> > 3) It may be that the volume control just needs more
> cleaning. 
> 
> Since the volume control is relatively noise-free AND this
> noise spike
> raises and lowers smoothly as the setting of the volume
> control is
> changed I'm pretty confident a dirty pot is not the
> issue.  The fact that
> the noise goes DOWN first, nulls out and then raises as you
> rotate the
> volume control clockwise still has me scratching my head
> though.
> 
> > 4) Is there a preamp stage (like a 12AV6 or something)
> before the 
> > 50C5? 
> 
> There is a 12AV6 preamp. I'll poke around in there.
> 
> > 5) Possibly the cartridge wiring? 
> 
> Aaron said "Make sure the connections at the cartridge are
> tight and
> wires properly 
> soldered and not broken. The leads can act as an antenna.
> "
> 
> This strikes me as perhaps the most likely culprit based on
> what I'm
> hearing. And it's definitely not something I thought to
> check before.
> Thanks, Aaron.
> 
> > 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.
> 
> The 60 cycle hum is not really objectionable. This morning,
> the buzz is
> also a lot less noticeable. Probably back to the level it
> was yesterday
> during the day when I couldn't really even notice it at
> normal playback
> levels.  I wouldn't expect a short here to generate or
> allow primarily
> the HF noise to get through but someone please correct me
> if I'm wrong
> about that.
> 
> Darren suggested H-K arcing. I'd be surprised if there was
> enough
> potential there to strike an arc, plus this is a VERY
> regular pulse, not
> random at all as I would expect an intermittant short to
> sound.
>  
> > 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.
> 
> Much, much less than half your age and very very into this.
> Hey, we talk
> about encouraging young people to get into aspects of our
> hobby. Now be
> careful what you wish for!
> 
> Thanks,
> --Dave
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