Unreliable turntable cartridge?

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Archived from groups: rec.audio.tech (More info?)

On Tuesday I bought an Audio-Technica AT-PL120 turntable. When I
put it together I was dismayed to find that while the left channel
seemed to work fine, I only got a loud hum in the right. I fiddled
with the connectors, and removed and replaced the cartridge a couple
of times, but nothing seemed to help. Then I removed the cartridge
shell one more time, poked very lightly at the exposed cartridge
wires with my finger, and when I replaced it again suddenly everything
worked! I removed and replaced it one more time just to be sure,
but it still worked.

Happy ending, as I did not look forward to repacking the thing and
lugging it back to the store! But now I'm nervous, and worried
that I might have a lemon that could go bad again at any moment.
So I'm wondering if anyone could tell me what the problem might
have been, and whether it was a commonplace setup glitch, or whether
it means the equipment is probably faulty. Any thoughts?
--
John Brock
jbrock@panix.com
 
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Archived from groups: rec.audio.tech (More info?)

In article <d1cmva$od5$1@reader1.panix.com>,
John Brock <jbrock@panix.com> wrote:

>On Tuesday I bought an Audio-Technica AT-PL120 turntable. When I
>put it together I was dismayed to find that while the left channel
>seemed to work fine, I only got a loud hum in the right. I fiddled
>with the connectors, and removed and replaced the cartridge a couple
>of times, but nothing seemed to help. Then I removed the cartridge
>shell one more time, poked very lightly at the exposed cartridge
>wires with my finger, and when I replaced it again suddenly everything
>worked! I removed and replaced it one more time just to be sure,
>but it still worked.
>
>Happy ending, as I did not look forward to repacking the thing and
>lugging it back to the store! But now I'm nervous, and worried
>that I might have a lemon that could go bad again at any moment.
>So I'm wondering if anyone could tell me what the problem might
>have been, and whether it was a commonplace setup glitch, or whether
>it means the equipment is probably faulty. Any thoughts?

The hum sounds to me as if you have a loose connection on one of the
cartridge contacts. On standard cartridges, there are usually some
small gold-plated springy metal contacts soldered to the wires, which
are slid onto the cartridge pins. I suspect that the fault may exist
at this point: either the solder (or crimp) junction on the contact
is intermittent, or the contacts are loose or "fatigued" where they
slide onto the cartridge pins and are not making a reliable connection.

Either of these problems will cause one side of the cartridge's
electrical connection to "float" - the cartridge will be disconnected,
and the wire will pick up 60-cycle powerline hum.

The fix is fairly straightforward - figure out where the connection is
breaking or becoming intermittent, and fix it. The fix may involve
re-soldering the wire to the contact, or gently squeezing the slide-on
contact so that it makes a firmer connection to the pin. [In either
case you should slide the contact off of the pin before trying to do
anything to it!]

It's also possible that the contact just hadn't been slid onto the pin
at all, I suppose, and was/is just held in place by the pressure of
the wire.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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