RCA Phono Wiring

Discussion in 'Tonefreaks' started by martin2hall, Jul 21, 2017.

  1. martin2hall

    martin2hall Senior Member

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    Hi Folks,

    Having had lots of very helpful advice here before, I'm hoping you good people can help...

    Not STRICTLY guitars but I'm trying to replace a damaged RCA male phono plug. I've picked up some non-solder plugs to make things 'easier'. :shock:

    All of the info online suggests that my cable (which in this case comes from a turntable) should have a single core and some insulation. However (as per my terrible diagram below) it seems I have three core wire. I figured it was double insulated but no matter what I do I am getting huge 'earthing hum'.

    Could someone simply point out which wire needs to go where?

    Fingers crossed here...

    <a href="http://s1356.photobucket.com/user/12mart12/media/20170721_121228_resized_zpshddt4js3.jpg.html" target="_blank"><img src="http://i1356.photobucket.com/albums/q723/12mart12/20170721_121228_resized_zpshddt4js3.jpg" border="0" alt=" photo 20170721_121228_resized_zpshddt4js3.jpg"/></a>

    <a href="http://s1356.photobucket.com/user/12mart12/media/20170721_121228_resized_zpshddt4js3.jpg.html" target="_blank"><img src="http://i1356.photobucket.com/albums/q723/12mart12/20170721_121228_resized_zpshddt4js3.jpg" border="0" alt=" photo 20170721_121228_resized_zpshddt4js3.jpg"/></a>
     
  2. martin2hall

    martin2hall Senior Member

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    Sorry, Pics error:

    20170721_121430_resized.jpg 20170721_121228_resized.jpg
     
  3. DarrellV

    DarrellV Murry Chrirstmers to earl! Silver Supporter Premium Member

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    upload_2017-7-21_8-40-45.png

    Your cable appears to have 2 shields. One could be signal ground and the other a chassis ground or something similar.

    Normally these 2 grounds are the same. Pics would help. Does this cable come out of the turntable itself?
    Pics of the inside of the turntable would really narrow this down, if it comes apart fairly easy......

    When assembling the connector make sure you put the jacket pieces on the cable first before making any connections, and be really sure that not even one strand of wire is touching between signal and ground or it won't work.

    I prefer a solder connector over what you are using because these can be a bugger to work with and aren't as reliable in the long run.
     
    Last edited: Jul 21, 2017
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  4. DarrellV

    DarrellV Murry Chrirstmers to earl! Silver Supporter Premium Member

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    In this case I would try the center conductor for hot, and the shield around it as earth.

    I would leave the outer foil and wire shield unhooked for now to see if it works. It may be redundant and can be cut cleanly off at the end and left unhooked.

    RCA jacks are mono by design. It takes 2 for stereo, so the 2nd shield is not needed.

    It may have been the wire they had laying around at the time..... Gibson would never do anything like this on a guitar.....:hmm::laugh2:
     
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  5. martin2hall

    martin2hall Senior Member

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    Hi, thanks for the reply!
    The cable comes straight out of the turntable, yes. I'll try and open it later for pics. It seems straight forward enough.

    if I twist the two shields together and attach them to the casing it hums. If I use just one, (either one) and tape the other off, it hums. I'm definitely not touching them together, or to the centre. Ive been very careful with individual strands.

    What do you mean by jacket pieces? The outer casing of the screw fit?

    Thanks again.
     
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  6. martin2hall

    martin2hall Senior Member

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    Ill try this!
     
  7. DarrellV

    DarrellV Murry Chrirstmers to earl! Silver Supporter Premium Member

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    This is where the 'cavity' pics of the turntable would help.

    Usually the other end of that cable is fastened to a terminal strip inside.

    The cartridge leads are then soldered to that strip to make the connection.

    It would be positive ID as to which wires you need to use, and from what you are saying, there may be something we are missing, or another problem under the hood causing the hum.

    You are correct, this isn't NASA stuff and it shouldn't be humming.
     
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  8. martin2hall

    martin2hall Senior Member

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    Ive done it!

    Ive put the middle wire to the casing and the centre to the hot and left the outer shielding unhooked. Clear sound, no hum!

    I must have had a crossover before.

    Thanks for your help DarellV. Really appreciated!
     
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  9. DarrellV

    DarrellV Murry Chrirstmers to earl! Silver Supporter Premium Member

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    That's the ticket! :thumb:

    I don't know why they do that kind of stuff with cable! :dunno:
     
  10. cooljuk

    cooljuk Transducer Producer Premium Member MLP Vendor

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    Turntables tend to have a chassis ground and a grounded shield on the output leads from the cartridge.

    If your turntable doesn't have a separate ground or a screw terminal on the back with a ground symbol to connect one, it might have been integrated into the output cable. Some use "zip wire" with two coax leads and a central ground conductor between them. Yours could be an alternate version of the same idea.
     
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