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Thread: Paolo's GR 1SF build

  1. #21
    Overlord of Music WeirdBits's Avatar
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    Photos of each part of the loom would help, from output jack to each pot and switch etc. Clear and close-up, if possible. Often times itís something that only other eyes can see.

    Common on things to check:
    Reversed output jack connections.
    Bad ground lug connection on a volume pot.
    Stray strand of wire from a Ďhotí brushing a ground point.

    Does it happen in all switch positions, are your getting sound from the pickups with a tap test, does either volume affect the hum? Sometimes disconnecting each pickup from the switch one at a time can help to narrow down where the issue is occurring.
    Scott.

  2. #22
    Quote Originally Posted by WeirdBits View Post
    Photos of each part of the loom would help, from output jack to each pot and switch etc. Clear and close-up, if possible. Often times itís something that only other eyes can see.

    Common on things to check:
    Reversed output jack connections.
    Bad ground lug connection on a volume pot.
    Stray strand of wire from a Ďhotí brushing a ground point.

    Does it happen in all switch positions, are your getting sound from the pickups with a tap test, does either volume affect the hum? Sometimes disconnecting each pickup from the switch one at a time can help to narrow down where the issue is occurring.
    Hi WeirdBits thanks for this.
    I checked through your list:

    Yes I get good sound from pickups tapping test.
    Yes it happens on all switch positions

    When both Neck and Bridge Vol pots are on 0 and Mast Vol is on 10, The noise has an added low Hum plus the buzz.
    When all 3 Vol pots are on 10 the low Hum goes.

    I checked ground lugs solder on Vol pots under jewellers glass, they looked strong but I added some solder on under side to be sure.
    Output jack is correct. Ground to inner sleeve.

    I also did a continuity test on the grounds with a multimeter - all seemed to pass.

    I disconnected Pickups one at a time at switch with No difference.

    So possible stray wire? on this third attempt I was very careful and the Pickup wires are divided and insulated.

    Could the problem be in a pickup?
    I will take picks and send tomorrow.
    Cheers

  3. #23

    Wiring GR 1sf

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  4. #24
    Member Swanny's Avatar
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    Have you checked the pots have continuity with the meter, and the resistance changes from the centre to outer lug when you turn the pots?
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  5. #25
    Overlord of Music Simon Barden's Avatar
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    Quote Originally Posted by BuffaloGhost View Post
    if its a hum that disappears when you touch the wires it sounds like an earth - when you touch that wire YOU effectively earth the wire.. hope you manage to sort it.
    This is a common misconception and you don't earth/ground the wire, touching the ground wire grounds you.

    When you connect direct to a good ground, either a) your body stops acting like an aerial picking up RFI and making any moise worse, or b) your body acts like a big ground plane and soaks up a lot of the RFI around, significantly reducing the level of hum (I'm not sure which, or it may be a combination of both).

    If you acted as a ground, then touching the signal wire would kill all noise- but instead it makes it louder. In this instance RFI being picked up by your body is being fed into the guitar signal, making the hum worse.

  6. #26
    Overlord of Music Simon Barden's Avatar
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    Whilst it shouldn't really make much difference in such a small circuit, it's worth checking that you haven't created a loop in your ground wiring as this can make hums worse. Breaking any loop might improve matters slightly. For instance, the white link between the toggle switch ground tab and the back of the master tone pot seems to form a ground loop. It looks like you were trying to achieve this from the diagram you sketched on your template, but you may have then added to it trying to kill the hum.

    But I'd be tempted to ditch the cloth covered wire and use screened cable instead. The runs between pots are quite long, so the wires can pick up a reasonable amount of noise.

    You can use the screen of single core screened cable to act as a ground between pots, but if you have several screened cables running to one device (such as the pickup selector switch), then only connect one of them to the ground connection (I normally use the output wire) and only have the screen connected to ground at one end for the others. The braid acts as a better screen if it han't got current running along it.

    The fact that you still have hum when both volume knobs are set to zero tells me that something's not right with the wiring or maybe the pots are damaged. When both pots are at 0, all the signal wires should be connected directly to ground, which should kill any noise. So with both of the pickup volume pots set to 0 and the master volume set to 10, I'd try measuring the resistance between the input and output lugs, the resistance between the output lug and ground and the resistance between the input lug and ground. All three readings should be as close to zero ohms as the meter will read. Do this with the selector switch set for the pickup volume pot you are testing to avoid the other pickup/pot affecting the reading.

    Also, have you got any major sources of electrical noise nearby? Fluorescent lights and dimmer switches are always bad for generating noise and the wiring can only pick up radiated noise that is around, it won't generate any. Try turning off anything that isn't essential in the room and see if the noise reduces.

  7. #27
    Overlord of Music Andy40's Avatar
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    I doubt its the pick ups at all. just check the resistance of them with your multimeter. I assume that you haven't got the ground and hot wires mixed around in one or both pickups? That wouldn't cause a grounding issue but it would cause some hum.

    It looks like there only one wire going to the jack? or is there two encased in heatshrink? If so, that would mean you have the earth wire running from the master tone to the jack instead of the earth coming bridge volume pot. I suppose it shouldn't matter (if everything is grounded well) but do you have complete earth continuity between the ground lug on the jack and the back of each pot and the earth lug on the switch?

    The solder joint on the earth lug on the bridge volume pot could be a little bit better. It may be fine now but could cause problems down the track in a hollowbody.

    Sorry thats all I can see mate.
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  8. #28
    Member Alexis's Avatar
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    Just in case: if you use a fluorescent lamp close to the circuit, it can add a lot of hum. It happened to me several times, until I remember to turn it off when I am testing the guitar circuit.

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