Thorens 145 hum

[Cheesehead]

Picked up a used TD145. Thought it was a bargain.
But when the arm approaches the last track it will often
go to a loud hum with no discernable audio.
Could this be the arm wiring?
Is this a problem you've noticed or has been documented before?

[Audio Empire]

On Thu, 26 May 2011 19:41:34 -0700, Cheesehead wrote
(in article >):

> Picked up a used TD145. Thought it was a bargain.
> But when the arm approaches the last track it will often
> go to a loud hum with no discernable audio.
> Could this be the arm wiring?
> Is this a problem you've noticed or has been documented before?

Yes It is the wire and yes I've seen it before on other 'tables. Usually it's
caused by a wire being twisted as the arm traverses the record at some point
causing a broken connection. Often it's the shield that parts, or perhaps
something shorts-out. You'll have to look. Best to remove the wires from the
cartridge and using an ohm meter, ring out each wire in turn while moving the
arm about and noting which wire loses continuity at some point in the arms
traversing arc. If you have to get the internal wiring replaced, you likely
cannot do that yourself, and it might not be worth having it done, even if
you can find somebody in this day-and-age who knows how.

[Audio Empire]

On Fri, 27 May 2011 06:00:10 -0700, Audio Empire wrote
(in article >):

> On Thu, 26 May 2011 19:41:34 -0700, Cheesehead wrote
> (in article >):
>
>> Picked up a used TD145. Thought it was a bargain.
>> But when the arm approaches the last track it will often
>> go to a loud hum with no discernable audio.
>> Could this be the arm wiring?
>> Is this a problem you've noticed or has been documented before?
>
> Yes It is the wire and yes I've seen it before on other 'tables. Usually it's

> caused by a wire being twisted as the arm traverses the record at some point
> causing a broken connection. Often it's the shield that parts, or perhaps
> something shorts-out. You'll have to look. Best to remove the wires from the
> cartridge and using an ohm meter, ring out each wire in turn while moving the

> arm about and noting which wire loses continuity at some point in the arms
> traversing arc. If you have to get the internal wiring replaced, you likely
> cannot do that yourself, and it might not be worth having it done, even if
> you can find somebody in this day-and-age who knows how.


I'd like to add, that while it COULD, conceivably, be the cartridge, itself,
it's unlikely. Reason? Usually the cartridge connections (internal and
external), don't move in relation to the arm, so were it the cartridge, the
hum probably wouldn't be related to the POSITION of the arm relative to it's
position on the record, but rather would either randomly come and go, or be
bad all the time. The exception might be if the cartridge itself were a
moving coil and the greater skating force toward the inner-grooves pulls on
one coil lead more than another causing a loss of connection on one of the
channels. Moving magnet or moving iron (variable reluctance) types of
cartridges have rigidly mounted coils and they don't ever move relative to
the cartridge body.

[Cheesehead]

I think it is shutoff circuit.
I'm going to look into a bypass or repair.u



On May 27, 12:33=A0pm, Audio Empire > wrote:
> On Fri, 27 May 2011 06:00:10 -0700, Audio Empire wrote
> (in article >):
>
>
>
>
>
> > On Thu, 26 May 2011 19:41:34 -0700, Cheesehead wrote
> > (in article >):
>
> >> Picked up a used TD145. =A0Thought it was a bargain.
> >> But when the arm approaches the last track it will often
> >> go to a loud hum with no discernable audio.
> >> Could this be the arm wiring?
> >> Is this a problem you've noticed or has been documented before?
>
> > Yes It is the wire and yes I've seen it before on other 'tables. Usuall=
y it's
> > caused by a wire being twisted as the arm traverses the record at some =
point
> > causing a broken connection. Often it's the shield that parts, or perha=
ps
> > something shorts-out. You'll have to look. Best to remove the wires fro=
m the
> > cartridge and using an ohm meter, ring out each wire in turn while movi=
ng the
> > arm about and noting which wire loses continuity at some point in the a=
rms
> > traversing arc. If you have to get the internal wiring replaced, you li=
kely
> > cannot do that yourself, and it might not be worth having it done, even=
if
> > you can find somebody in this day-and-age who knows how.
>
> I'd like to add, that while it COULD, conceivably, be the cartridge, itse=
lf,
> it's unlikely. Reason? Usually the cartridge connections (internal and
> external), don't move in relation to the arm, so were it the cartridge, t=
he
> hum probably wouldn't =A0be related to the POSITION of the arm relative t=
o it's
> position on the record, but rather would either randomly come and go, or =
be
> bad all the time. The exception might be if the cartridge itself were a
> moving coil and the greater skating force toward the inner-grooves pulls =
on
> one coil lead more than another causing a loss of connection on one of th=
e
> channels. Moving magnet or moving iron (variable reluctance) types of
> cartridges have rigidly mounted coils and they don't ever move relative t=
o
> the cartridge body.