Re: unit hums loudly regardless of volume
- From: "tempus fugit" <toccata@xxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 31 Oct 2005 13:18:17 -0500
I tested the cap and it showed about a half meg of resistance. maybe
something is shorted somehwere else. Oh, and I checked the voltage between
the record player chassis and the scope chassis - 120VAC (I thought that's
what it felt like). Odd though, I would think with 120v on the chassis that
it would pop a fuse at the breaker box.
Thanks
"CJT" <abujlehc@xxxxxxxxxxx> wrote in message
news:43665638.5000307@xxxxxxxxxxxxxx
> CJT wrote:
>
> > tempus fugit wrote:
> >
> >> Tried the turining around the plug trick, but it made no difference. I
> >> also
> >> disconnected the phono plug that connects the tone arm to the amp unit,
> >> which also made no difference.
> >>
> >> Here is something curious though. I accidentally touched my scope
> >> while my
> >> hand was on the record player chassis and got a fairly good shock. The
> >> scope
> >> has a 3 prong AC plug (the record player doesn't). I should've
> >> measured the
> >> voltage difference between the sope chassis and the record player
> >> chassis,
> >> but I didn't think to. I'll have to do that. Perhaps he chassis is
> >> live. I
> >> didn't think this would be the case though, since there is a cap with
the
> >> negative connected to the case, as well as a few other green wires.
> >>
> >
> > That capacitor might be leaking or (worse) shorted. It can be a lethal
> > failure (I read just this week about a minister in Waco who was
> > electrocuted during a baptism when he grabbed a microphone that was
> > "hot."). Be careful.
> >
>
> Here's a cite to that story:
> http://www.cbsnews.com/stories/2005/10/31/national/main995829.shtml
>
> >> Thanks
> >>
> >>
> >> "Asimov" <Asimov@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
> >> message
> >> news:MSGID_1=3a167=2f133.0_43612958@xxxxxxxxxxxxxx
> >> "tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
> >> --- on the heady topic of "unit hums loudly regardless of volume"
> >>
> >> tf> From: "tempus fugit" <toccata@xxxxxxxxxxxxxxxxxxxx>
> >> tf> Xref: core-easynews sci.electronics.repair:346437
> >>
> >> tf> Hey all;
> >>
> >> tf> I'm trying to repair an old tube portable record player. When it
is
> >> tf> on, it hums really loud, regardless of the volume.
> >>
> >> Have you tried turning the ac plug around?
> >>
> >> Which way the plug is inserted matters with these. Let the record
> >> player warm up, then insert the plug one way or the other, and then
> >> paint a mark for which was the quietest way. One way: lots of hum, the
> >> other: quiet hiss.
> >>
> >> Those old tube units used to get B+ directly from the powerline (or
> >> sometimes a voltage doubler) and used a large value resistor bypassed
> >> by a 0.01uF to RF ground the tone arm shielding to neutral. The power
> >> for the filaments often came from a secondary winding in the motor
> >> coil. Don't use this type of record player near the bathtub. Lethal!
> >>
> >> Another possibility is a broken wire at the cartridge.
> >>
> >> A*s*i*m*o*v
> >>
> >> ... Just a little force field zap.
> >>
> >>
> >
> >
>
>
> --
> The e-mail address in our reply-to line is reversed in an attempt to
> minimize spam. Our true address is of the form che...@xxxxxxxxxxxx
.
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