Early AR XA turntable restore found three wires coming out of tonearm.

[cmarti]

I got this table from a local seller, he was the original owner and it seems to be on of the earliest incarnations of the AX model because it has two motors instead of one.

As I was removing the Pickering v-15/am1 that was on it with the intentions of installing a new old stock Shure 500S I noticed that both ground connectors for the cart left and right channels were soldered together (joined)

I thought that was weird and separated them, did the whole maintenance to the table and when I rested it I heard a loud hum on the left channel. I was like what? So swapped carts and checked the continuity of the tonearm wires as all looked normal... Then I noticed that only three wired come out of the tonearm and one ground was missing, keep in mind this is a 100% stock table from probably 1964.

I thought and brainstormed and remembered the fact that the negative leads for the card were soldered together so I went ahead and soldered them back as they were original, so I reconnected everything and there was no more hum and pulled out my old trustworthy Hi-Fi stereo records and the turntable passed all tests.

Now, why do I only have three wires coming out of the tonearm and what is more important does anyone think I will suffer from sound quality degradation because the ground leads for the carts are joined? That is what worries me the most, I am used to seeing separate leads for positive and negative leads from the carts all the way to the RCA plugs.

Here are some pictures which might help give some more understanding. https://imgur.com/a/9R1Wr

Thanks for the support guys!

 

[marcmorin]

The arm has been rewired, that's not factory. makes no difference if the grounds for the cart are summed at the back of the cart, back of the headshell socket, or like 99.9% of every table out there, summed at the preamp. provided both channels have a ground.

 

[cmarti]

The arm has been rewired, that's not factory. makes no difference if the grounds for the cart are summed at the back of the cart, back of the headshell socket, or like 99.9% of every table out there, summed at the preamp. provided both channels have a ground.

So in short I am good?

I can hear awesome channel separation and since it passed the test disk I assume there should be no problem.

 

[marcmorin]

So in short I am good?

I can hear awesome channel separation and since it passed the test disk I assume there should be no problem.

I sum both channel grounds and TT ground on ARs at that wire tree. makes for less noise. the earliest stereo carts only had 3 pins, I believe it was Shure who started the 4 pin set up

 

[woodj]

I sum both channel grounds and TT ground on ARs at that wire tree. makes for less noise. the earliest stereo carts only had 3 pins, I believe it was Shure who started the 4 pin set up

Marc, Good to know that. It was a logical way to do it though.

 

[cmarti]

I sum both channel grounds and TT ground on ARs at that wire tree. makes for less noise. the earliest stereo carts only had 3 pins, I believe it was Shure who started the 4 pin set up

Thank you Marc, it is indeed dead silent. The only thing you can hear is a little motor rumble but not wiring humming at all.