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QUESTION: Ariston Turntable Voltage Polarity

I picked up an Ariston Q Deck turntable at a thrift shop recently, but it did not come with its 12v wall AC adaptor.

The back of the unit simply says "12V DC 350mA" but gives no indication of the polarity of the AC adaptor. I can find a 12V DC adaptor that can supply the recommended mA output, but I want to be sure about the polarity.

The socket for the adaptor is the standard type round hole with a male connector in the middle.

MY QUESTION: To properly power this turntable, what polarity should I look for in the AC adaptor's female connector---in other words, what part of the female connector should be positive (+) and what part should be negative (-) ?

Inside hole positive and outside sleeve negative, or the other way round?

Many thanks in advance.........

Reply to
EADGBE
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When these DC connectors were first around, the convention was (oddly) "-" to centre. In more recent years, the convention is almost invariably "+" to centre. It is very possible that the turntable signal ground will be shared with the DC supply ground, so as a first move, just try your meter on its lowest ohms range, and see if the socket outer is common with the signal cable screen, or with the separate signal ground wire (usually black) if one is fitted. Any metal parts on the deck, will also almost certainly be connected to the DC ground.

Failing this, you wil need to go inside the deck. The motor is usually a 'pattern' cassette-type motor, where the terminals are clearly marked "+" and "-", ( "A" and "B" might also be there to go out to external speed-set pots for 33 and 45) so it's just a case of following the "-" marked terminal back to the socket. The "+" marked one will route back to the socket via the power control switch(es). There may be an electrolytic cap across the power leads also, for decoupling purposes. The polarity markings on this, if fitted, would also tell you the correct way round.

Just as a matter of interest, these motors are pretty robust against reversed polarity, at least for short periods. All That normally happens, is that the control electronics mounted inside the motor, go berserk, and just run it at high speed, backwards.

Arfa

Reply to
Arfa Daily

Arfa:

For what it is worth, there is continuity between the contact that touches the SLEEVE of the female connector and one of the turntable's motor mounting screws. There is also very low resistance.

I couldn't get any kind of reading from any part of the signal wires or the external ground wire....strange!

So based on these observations, I'm leaning toward the assumption that the centre of the female connector has to be positive (+), and the sleeve is negative (-).

Reply to
EADGBE

Easiest way is to open it up and look at the polarity of capacitors ground if it has electronics as well as just a motor. In other words trace the ground to the PCB and where a capacitor is connected directly to it.

If it is just a motor with no electronics it will likely just run in the wrong direction with reverse polarity.

--
*I'm pretty sure that sex is better than logic, but I can't prove it.  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.
Reply to
Dave Plowman (News)

I have one of these record players. I set the polarity by connecting the power and seeing which way the platter turns! It does not seem to do it any harm.

Reply to
philicorda

That would be my thought also. Sometimes with turntables employing DC motors, the signal ground is not commoned with the DC ground, to avoid introducing motor brush-gear noise into the following amplifier. A motor mounting screw going to the sleeve connection on the socket is pretty conclusive though, as the case of the motor usually has a tab down by the connector board, which solders straight to the "-" connection.

Arfa

Reply to
Arfa Daily

maybe vinylengine.com 's library or forum section has the manual so you can check?

Reply to
b

Here's an update on the polarity of the Ariston turntable.

I removed the unit's base cover plate on the bottom, and all of the wiring was plainly visible. The red wire was attached to the centre contact of the voltage input jack, and the black wire was connected to the sleeve contact.

I bought an AC adaptor with the correct female plug on it and made sure that the positive contact was the centre.

Plugged it in, switched on the turntable, and SUCCESS!

The turntable works perfectly.

Thanks to everyone for your assistance with this! :-)

Reply to
EADGBE

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