[Jukebox-list] A Wurly 2510 amp question

[Steve Wahl]

On Thu, Sep 20, 2007 at 07:49:54AM -0400, Jjmscf at aol.com wrote:
>  
> Mono 2510s should have a ceramic cartridge.  The first model to do so.
> ...  So the needle itself only makes a mechanical connection, not an
> electrical.  It's a standard flipover needle.  She stated she changed
> the entire cartridge.  It is also the same cartridge as the stereo
> version wired for mono so she would have had to deal with the little
> push on clips attached to those delicate tone arm wires if she
> changed the cartridge. Wonder if she broke a tone arm wire?

J.C.,

So do I hear you right, there's a stereo cartridge feeding a mono amp?

How did Wurlitzer originally wire it, with the channels in parallel,
or in series?  (Or did they just use one channel of the cartridge?  I
doubt that.)  Are there four pins or three on the cartridge?  (I
believe some ceramic carts, not necessarily ones used in jukeboxes,
had a single common ground; I can't remember what it looks like on my 2410s.)

Thinking along the lines that the person who replaced the cartridge is
of unknown technical ability: If there are four pins, I can think of a
couple ways to screw up the wiring so it looks OK but yields no
sound.

If wired in series, there would need to be a jumper between the - of
one channel and the + of the other channel, with the lead to the amp
connecting to the remaining pins.  If you mistakenly connect the
jumper to both + pins, and the outputs to both - pins (or vice-versa),
you'd get a phase cancelation, which would greatly reduce the output
of a mono record, or make a stereo record sound "hollow", but I
wouldn't expect silence.  BUT, if you leave the jumper off because you
didn't know you had to transfer it from one cartridge to the other,
you would get silence.

If wired in parallel, each lead to the amp would connect to two pins;
one to both + pins on the cartridge, the other to both - pins.  If you
swap two of the pins by accident, you can connect one lead to the +
and - outputs of one channel, and the other lead to the + and -
outputs of the other channel, shorting both out and sending nothing to
the amp.  (A different set of swapped pins could end up with the phase
cancelation problem, like above.)

So, I'm thinking it might be worth inspecting the cartridge
connections even closer than just looking for a broken wire.
Esp. if the finger-to-the-amp input method gives a hum.

Oh, and of course the muting circuit ought to be checked out as well.

--> Steve

-- 
Steve Wahl    steve at pro-ns.net

One day, the light bulb in the fridge burnt out, and I thought to myself,
"At least now I know it's off when the door's closed... Or do I?"