How is a 5120 supposed to be wired?

Discussion in 'Technical Side of Things' started by sluttyhearts, Dec 10, 2019.

  1. sluttyhearts

    sluttyhearts Electromatic

    Dec 10, 2019
    Portland, Oregon, USA
    Hey, all—

    Longtime lurker, first time poster, yada yada, thanks for your patience.

    I'm having a buzz (grounding) problem with my G5120. I replaced the stock pickups with some TV Jones a year or two ago, and even though I was a noob, it seemed like it was working OK. Then the wood around the output jack got munged (stop me if you've heard this one) and I invented a repair involving a Les Paul jackplate. (It later transpired that I was not exactly the first yahoo to think of this, but I was still kind of proud of myself.)

    During all these repairs, I noticed that the factory wiring is super cheap. Gretsch seems to have gone with 2¢/ft. wire instead of 7¢/ft. wire on this model, making the wiring harness approximately 1000x less sturdy to save 15¢. (If anyone at Gretsch is reading this, I just want to say I would totally have paid the extra 15 cents to not be dealing with this. Hell, I'd probably pay a quarter!) If, in the course of soldering a connection, you bend the wire more than twice, it breaks.

    The upshot of this is a) high blood pressure, and b) all the wiring slowly getting shorter as I cut off the broken ends and start over. So I just want to pull it all out and rewire it, using the nice new guitar wire I ordered from Stewmac.

    But imagine my chagrin at learning that neither, nor, apparently, anyone else on the Internet, has a wiring diagram that is specifically stated to work for the 5120.

    There's this, which lists a bunch of model numbers, but 5120 isn't one. And there's this, which seems promising, but who knows?

    You may ask, why don't I just replicate whatever wiring is in the guitar currently? Well, as it turns out, the only knob on my guitar that seems to do anything at the moment is the master volume. Since that's the only one I use on the regular, I didn't notice till I started trying to track down the grounding problem. But currently—and make no mistake, this is clearly my fault—the guitar is wired wrong.

    Can anybody steer me toward a schematic that, if followed correctly (a big if, I admit), will restore my 5120 to its factory configuration?
    calebaaron666 likes this.
  2. ramjac

    ramjac Synchromatic

    Aug 14, 2011
    Those diagrams are essentially two different representations of the same circuit (the second one shows a treble bleed capacitor that you can omit if you like. It is the correct circuit for the 5120 and is often referred to as the Gretsch tone pot circuit. There’s also a good pdf available at the TV Jones website.

    Which leads me to the point I’d really like to make, which is that you should save yourself the trouble by returning that wire to Stewmac and instead buying a ready made tone pot harness from TV Jones. Seems pricey at $105, but wiring inside a hollow body guitar is misery itself. I’ve made custom harnesses for lots of things, including guitars, but it’s one thing to build a DIY harness from scratch for, say, a Gretsch Jet, where you have good access, and another to try it on a hollow body. With the TV Jones harness, you’ll get upgraded pots, switch and jack, and it’s pre made to fit so you can get straight to the business of trying to stuff it inside the guitar. Not doubting your abilities in any way, but time is money and better spent playing than cursing your guitar.

    EDIT: You could also just troubleshoot it. Less money than a new harness and way less time and frustration than building a DIY harness. In fact, I think the solution to your problems may be fairly straightforward.

    1. As far as the independent pickup volume pots not working, what probably happened was that instead of soldering one of the leads of the neck pickup to ground (black + bare shield to neck pot casing) and the other lead (white) to the center lug (wiper) of the neck volume pot, you soldered one pickup lead to ground and the other lead to the same lug on the neck volume pot that connects to the selector switch, with nothing connected to the center lug. Thus, instead of seeing a variable resistance when you adjust the neck volume, the neck pickup always sees the full resistance of the pot - wide open volume. Exact same analysis for the bridge pickup. Given that you never use the neck or bridge volumes, you could just leave things as they are - it’s just a permanent wide open volume and won’t be a problem UNLESS you have the white lead going to ground and the black + shield going to the selector switch - then your shield isn’t properly grounded and can lead to noise issues. So maybe just check both volume pots to ensure proper grounding to the casing for each pickup. If you want the volume pots to work, make sure the white lead goes to the center lug (leave the harness wire connecting the pot the selector switch alone - check against the diagrams you posted above to confirm).

    2. Not sure when you started noticing the ground problem, but if it started when you damaged the output jack, it could be that the ground wire for the bigsby was yanked loose and now your strings are no longer grounded. Shine a flashlight into the guitar body to locate the wire and try to snag it lightly to see if it’s disconnected. It will be a single thin black wire coming from the output jack. Let me know if this is the case and I can send you details on how to repair it.
    Last edited: Dec 10, 2019
    sluttyhearts and Jeff67 like this.
  3. Jeff67

    Jeff67 Gretschie

    Nov 3, 2019
    Crockett, Texas
    This really is the best idea! Also, if you can swing the $105 for the harness, do yourself a huge favor and spend the extra $8.50 for the treble bleed kit and $8.00 for the installation kit. You'll be glad you did!
    sluttyhearts likes this.
  4. wildeman

    wildeman Gretschified

    May 10, 2015
    I could rewire a 5120 in about 2 hrs with 30 to 50.00 worth of parts ( excludes pickups) and i've been messing with guitars for 25 years. I think a pre made harness is a MUST if you don't have experience, unless you have the patience of Ghandi. Trust me, it will not be an enjoyable first re-wire.
    BorderRadio, sluttyhearts and Outlaw like this.
  5. calebaaron666

    calebaaron666 Country Gent

    Aug 15, 2018
    Portland, Maine
    Welcome! I love your avatar pic. Ivy is my ultimate guitar Goddess. She’s one of the main reasons I play a Gretsch. My 5420 is named Marlana after Ivy’s given middle name.
    I replaced the wiring in this guitar with a prewired TV Jones wiring harness. All I had to do to the harness was solder the pickups to their respective volume pots. I bought a busy harness with extra stuff (tone switch, kill switch), and I paid about $130. It wasn’t cheap, but after all is said and done, I have no regrets.

    However, if you only use the master volume, maybe consider buying the “hot rod” harness. It’s a little cheaper. It’s as simple as it gets. Pickups, selector switch, volume, output jack. You could keep the other knobs in your guitar for decoration.
    Just a thought.
    G5422T, sluttyhearts, audept and 2 others like this.
  6. thunder58

    thunder58 Super Moderator Staff Member

    Dec 23, 2010
    tappan ny
    Admin Post
    Not sure if this helps .... this came out of my 5120 . Long gone but I hope you can follow this and hope it helps IMG_0277.JPG
    sluttyhearts likes this.
  7. sluttyhearts

    sluttyhearts Electromatic

    Dec 10, 2019
    Portland, Oregon, USA
    Hey, sorry to post and ghost. Thanks to all who helped; I feel a bit more confident now.

    I know that the ideal answer is to buy that pre-wired harness from TV Jones, but I can't (or at least shouldn't) spend the money right now. So I'm going to do the stupid thing and try to rewire it myself. I'll have two weeks around Christmas when my bandmates will be doing family stuff, so I'll have some breathing room if things go sideways.

    As I mentioned above, I've already changed the pickups and replaced the output jack, so I have a fairly good idea of how much of a pain it's going to be. But I figure I can pull out all the guts at once, and then use the trick where you "install" your pots and switches in a piece of cardboard in the same positions that they'd be on the guitar.

    Then I can at least wire it up in the open, rather than through a keyhole. And after that, the hardest part will be getting the new wiring harness back into the guitar—which I'd still have to do even if I bought the pre-wired harness.

    I'll try to get some photos of the process so you all can share in my joy/humiliation, and so the next poor guy can see what to do (or not do). But if I die, all bets are off.
    BorderRadio and calebaaron666 like this.
  8. thunder58

    thunder58 Super Moderator Staff Member

    Dec 23, 2010
    tappan ny
    Admin Post
    Lots of tips and tricks on You Tube regarding ( just type in ) " TV Jones Wiring Harness "
    Perhaps it may help in re-installing your wiring " harness "
  9. audept

    audept Senior Gretsch-Talker

    Dec 1, 2010
    Sydney, Australia
    Welcome to the forum, sluttyhearts!
    welcome mat 110.jpg
  10. DennisC

    DennisC Synchromatic

    May 11, 2017
    It is by no means stupid to wire the guitar yourself!

    Basically, compared to real complex electronics a guitar is a pretty simple thing ... two source-devices, here exchanging energy from string motion via bending a magnetic field into electric current, a selector switch and a liitle bit of filtering and a jack.

    In a hollowbody, it really is getting the stuff out and in again that makes it ... well, suck. Tubes on the pots and switches shall help to relocate them or locate the new ones, you can pull them into place that way.

    Honestly, I don't doubt TVJ makes the complete wirings from well known and reliable components, or that they are experienced and well-abled workers - but I may be a DIY-kind of guy too much to buy a complete harness instead of making one myself.

    An aid to place the stuff on, with the restrictice guts of the guitar, like soundpost or other bracing elements, centerblock and the like, should at least help avoid too short cables ... and 1 or 2 inches too much won't hurt no one, especially when you use shielded cables, but even when you don't, this isn't gonna result in any catastrophe.
    new6659 likes this.
  11. Lizardkinged

    Lizardkinged Friend of Fred

    Oct 5, 2009
    Holy cow... That's sitting in my parts drawer!
    thunder58 likes this.
  12. thunder58

    thunder58 Super Moderator Staff Member

    Dec 23, 2010
    tappan ny
    Admin Post
    AH - HA !! couldn't remember which member it went to
  13. G5422T

    G5422T Country Gent

    May 24, 2012
    To the OP. Whatever route you take, add the master volume treble bleed. IMO, well, well worth it.

    Makes the master volume very usuable with out losing highs when you lower the volume.

    Best of luck and take your time. Pics are always welcomed
    BorderRadio and DennisC like this.
  14. sluttyhearts

    sluttyhearts Electromatic

    Dec 10, 2019
    Portland, Oregon, USA
    What value for the treble bleed cap? .022 or .047? Or something else? (FWIW, I'm a guy who likes a fair bit of treble...)
  15. G5422T

    G5422T Country Gent

    May 24, 2012
    Here's what I've been using. I have no local access, so you can use any brand that you prefer.

    Works well for my Gretsches.
  16. BorderRadio

    BorderRadio Country Gent

    Mar 6, 2014
    Phoenix, AZ
    It's really not that hard to make a harness, but the first time will take some time. I also agree, you should set it up on cardboard with the outline and positions replicated. I do the same on masonite board, since I was at one time selling harnesses. This allows me to make only one solder connection at the guitar: the tailpiece grounding wire. I also added a clip-in/solderless system for making pickup swaps a breeze. To make a quality harness, I'd be spending about 45 bucks retail, so it's worth the savings if you have patience and like to build things. The actual installation isn't terrible either, compared to a semi-hollow/center-block instrument. Now those types of guitars drive me nuts during installations, and thread and f-holes are sometimes the only option, with multiple solder points at the guitar itself.

    I'd use the standard TVJ-spec set, 15ok resistor and 0.001uF cap in parallel.

    Also, for the FYIs for guys who don't want to make their own loom, Sigler/920D has a nice harness with quick connects.
  17. sluttyhearts

    sluttyhearts Electromatic

    Dec 10, 2019
    Portland, Oregon, USA
    Hey, all—

    Just wanted to update as to what ended up happening with my 5120—I often come across threads like these when trying to solve a problem, so I figured I'd put the solution in writing in case someone else in the distant future comes here looking for answers.

    The upshot: I wimped out, and instead took ramjac's advice

    I decided that before I went crazy gutting the guitar, I could at least check and see whether the strings were grounded. Using a multimeter, I checked for continuity between the tailpiece and the ground (shaft) portion of the output jack. Nada.

    I then ran a wire, externally, from the tailpiece to the output jack (basically treating the strap button and output jack nut as screw terminals), and plugged into my amp. Grounding issue was gone.

    So it was just the grounding wire after all! Hmm, wonder what happened to it? Aahh, who cares? I removed the tailpiece to reveal the little hole in the bottom of the body that the grounding wire goes through on its (internal!) way from the tailpiece to the output jack, and ran my own brand new wire through there. I fished out the other end and, having already removed the output jack, I soldered my new ground wire onto the shaft connection of that and replaced it all in the body, using the standard, profanity-inducing laparoscopic procedure well-known to most of you.

    During the course of this process, I came across the original ground wire flapping around in the body—still attached at the tailpiece end, but loose at the other. Must have come loose from where I'd soldered it to the shell of the bridge pickup volume pot last time; I remember that connection gave me a lot of trouble back then, when... wait, what?

    Yes, you read that right: For some reason, the last time I'd worked on this guitar I had attached the grounding wire, not to the output jack, but to the aforementioned pot. (Which is connected to ground, supposedly, but apparently not in the right way.) God only knows what I was thinking. I had even spliced an additional length of wire onto the end of it so it would reach the pot, all the while cursing Gretsch for not leaving enough slack in the wire to make the job easy.

    So, I now had a (sorta) working guitar—no grounding issue! Of course, there was still the fact that neither of the pickup volume pots worked. Emboldened by my relative success, I decided to press on...

    I pulled out the bridge pickup pot and was disappointed to see that it was wired correctly. Then, just for the hell of it, I plugged in the guitar and gave it a twiddle. Now it worked! Maybe it didn't like the way I'd connected it to the grounding wire before, and now that that was gone, it was OK? Whatever; it works now, so close enough.

    I then checked the neck pickup, and sure enough, it was exactly as ramjac predicted:


    Nothing connected to the wiper, so no way for the pot to do its job. I quickly corrected this and boom, everything now worked! I quickly reassembled the guitar before it changed its mind, and so far so good.

    MORAL OF THE STORY: This is directed at those poor future slobs who might read these words looking for a solution to their own guitar troubles. There's one difference between the guy who put in those pickups and miswired his guitar a year ago and Modern Me, who more or less managed to fix that guitar: The latter took 20 minutes to read "Understanding Guitar Wiring" at the Stewmac website.

    It doesn't have to be that particular site, there are lots of other places that have the same info. The point is, there's a big difference between blindly following instructions (or trying to match your work to a diagram, or just hoping to put everything back exactly as you found it) and having at least a rudimentary understanding of why you're doing what you're doing.

    I'm still an idiot, and God knows I exhausted every possible alternative before finally breaking down and learning something, but it really did help. (Finally understanding how pot lugs work was worth the price of admission all by itself!)

    Remember, kids, there's no substitute for education. Now shut up and get off my lawn.
    Last edited: Dec 31, 2019
    new6659 likes this.
  18. wildeman

    wildeman Gretschified

    May 10, 2015
    Wait till you get to the next level, just looking at that stuff and being able to SEE what its doing.
    Sean McILwaine likes this.
  19. Henry

    Henry Gretschified

    Apr 9, 2014
    Good for you. I have regressed. My next and only level is to take it to the luthier. The rest of my life causes enough stress.
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