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Thread: 50s Wiring Help

  1. #1

    50s Wiring Help

    Hi all, new guy here. I'm an extremely novice 10 year player, self taught & not very good at all. I also like to tinker. So, I have a 2004(5-ish) Chinese Epi LP (EE serial number prefix) & I decided to upgrade it. I bought some Slash PuPs, and a premium wiring kit from Stewmac to wire it up 50s style. I work in engineering, and have spent many years as a mechanic, so I'm good with tools & schematics etc. I spent a good amount of time online watching various wiring videos & reading up on it all prior to starting. I made a template of the pot holes on some strong cardboard and wired up the pots & caps outside of the cavity, then I wired the switch & started installation. I noticed that the long shaft of the switchcraft switch caused the base of the switch (where the wire connections are) to not line up with the passthough hole for the wires, so they have to be bent back "up" towards the top of the guitar before routing. After re-assembly (bad move), i have the following problem:

    Neck position - neck pup is good, vol & tone works.
    Middle position - neck pup is good, vol & tone works, nothing from the bridge pup
    Bridge position - heavy buzz like a ground short. no sound or tone from pup.

    When i test the ground (from pot to each component) its all good. Testing the pups through the output jack does not work, but isolated testing them is good. Not sure where to go with it now, could it be a bad switch, or the fact that the switch posts touch the wood? I've also read that with the single conductor pushback wire its possible to "overheat" it when soldering, and ground the wire out... not sure if this is true or if its the case, but if so, i cut my pup leads to fit, is there a way to replace them?

    any suggestions? I've searched the forum and the internet, and couldnt find a similar problem, so i had to post. thanks in advance

  2. #2
    Les Paul Forum Member
    Join Date
    Jun 2007
    Location
    England
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    Re: 50s Wiring Help

    As you say it is possible that the shielded wire can be damaged by excessive heat, particularly when soldering the outer braid to the back of the pots it can melt the insulation so that the inner conductor shorts to ground. This can often be very difficult to see but close examination with a magnifying glass under good light might show if this has happened, testing for shorts with a multimeter may also show this up, check for continuity between the centre conductor and ground with the volume pots on 10 - there should be no continuity.

    You say that testing the pickups at the output jack does not work? With the volume controls on 10 if you measure the D.C. resistance across the jack you should get a reading which is close to the D.C. resistance of whichever pickup is selected, if not there is a wiring fault somewhere so recheck all your connections.

  3. #3

    Re: 50s Wiring Help

    Quote Originally Posted by PaulD View Post
    You say that testing the pickups at the output jack does not work? With the volume controls on 10 if you measure the D.C. resistance across the jack you should get a reading which is close to the D.C. resistance of whichever pickup is selected, if not there is a wiring fault somewhere so recheck all your connections.
    Correct. If i perform this, the neck position measures in range. The middle position measures in range & the bridge position measures 0.0

  4. #4
    Les Paul Forum Member
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    England
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    Re: 50s Wiring Help

    That tends to suggest there is either a problem with the wiring of the bridge pickup or with the switch itself. I would check all of the solder joints, if they are OK remove the switch and have a look to see that contacts are making and breaking properly when you move the toggle (you can see the operation of the 2 spring loaded contacts clearly with the switch removed). When you say it measures 0.0 do you know if it is open circuit (infinite resistance) or short circuit (zero ohms)? Some meters will read 0.0 for both but if you have a continuity function you can check with that, if it reads continuity it is a short circuit.

  5. #5
    Les Paul Forum Member
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    Aug 2017
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    Weston super mare , engalnd
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    Re: 50s Wiring Help

    watch that nothing is touching the inside of the switch cavity or any other cavity for that matter , that inocent lookin black matted paint is conductive in those chinese epi's

    so the wall of the cavity's are connedted to ground

  6. #6
    Les Paul Forum Member
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    Re: 50s Wiring Help

    Quote Originally Posted by GeraintGuitar View Post
    watch that nothing is touching the inside of the switch cavity or any other cavity for that matter , that inocent lookin black matted paint is conductive in those chinese epi's

    so the wall of the cavity's are connedted to ground
    That's a good point! I didn't realise they had conductive shielding paint so that would probably be the first thing to check.

  7. #7

    Re: 50s Wiring Help

    Quote Originally Posted by PaulD View Post
    That's a good point! I didn't realise they had conductive shielding paint so that would probably be the first thing to check.
    Didn't realize that either, gave it a check last night but no luck. There's definitely a ground in the bridge loop, and at this point i suspect its either the switch or pup lead that got too hot and melted the insulation, unless there was some solder drip down the lugs. I didnt get too much time to mess with it so ill probably pull everything out tonight and see. I also have a new (short body) switch coming on monday which ill install. If the pup was grounded out, wouldn't i still get sound from it?

  8. #8
    Les Paul Forum Member
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    England
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    Re: 50s Wiring Help

    Quote Originally Posted by raiderbob View Post
    If the pup was grounded out, wouldn't i still get sound from it?
    No, if it was grounded all the output is shunted straight to ground and it would be silent (same as having the volume control on zero)

  9. #9

    Re: 50s Wiring Help

    Quote Originally Posted by PaulD View Post
    No, if it was grounded all the output is shunted straight to ground and it would be silent (same as having the volume control on zero)
    By that you mean silent as in ....no output.... but there's still the heavy buzz coming through the amp on that switch position (like when you grab the end of the guitar cable while its plugged into the amp and powered on).

  10. #10
    Les Paul Forum Member
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    Jun 2007
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    Re: 50s Wiring Help

    If it was a dead short to ground it would be completely silent but dodgy solder joints and poor / intermittent connections can cause buzzing noises. As well as looking for shorts on the wires I would also double check all of your solder joints, particularly the ground connections as bad grounds are a common cause of hum and buzzing.

  11. #11

    Re: 50s Wiring Help

    Turns out the bridge pup was dead. Not sure if it shipped that way or if i somehow damaged it, but amazon rules. New pups arrived yesterday & i metered them... they both work lol. Ill be re-installing it all tonight. Hopefully i can post good news later.

  12. #12

    Re: 50s Wiring Help

    Aaaaaaand done. Re-installed/wired everything up last night and all is good. also, this upgrade shreds! thanks for the help all.

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