Les Paul with a Hum

No, it doesn't "hum along with the music" it just hums.

Long story: My 81 Les Paul Custom had its stock pups replaced in 1981 shortly after it was purchased. The person who did it was a complete hack... ok, it was me, I was 16, had a radio shack soldering iron, etc... I bought the guitar brand new and for some reason replaced the stock pups. Dumb, I know, I wish it never happened, I wish I still had the stock pups, I'd put 'em back in now, but I don't. In the neck position is a Dimarzio PAF and a Bill Lawrence L-500 in the bridge. Aside from that, I somehow managed to not wreck the guitar and it made it through the rest of my youth. It's got some wear and tear, but it's still an amazing player.

Fast forward to now: I'm not such an electronics hack anymore, but I still have my Les Paul with its assed-up pickups.

The guitar has a definite 60 cycle hum. When I touch the output jack, the hum is reduced greatly. Must be a ground problem. There is no "bridge" wire, like my tele and strat have, so touching the strings has no effect. The guitar is shielded throughout in the cavity by the stock shielding in the pickup selector cavity and the potentiometer/control cavity.

Since last week, I've gone through the wiring and cleaned up the soldering drastically. This hasn't made much of a difference in the hum, but I feel better about the guitar, that I've some what atoned for my youthful sins.

Questions:

1. Did some Les Pauls have a wire to the bridge to ground the guitar through the strings and player? Would it be a good idea to add one?

2. Is it possible the open face pickups are to blame for this hum? The L-500 is encased in metal, so I think it's pretty well shielded. The dimarzio PAF is not.

3. Any other suggestions for fixing the hum?

Well I think you need to rewire it, and fix the ground connetions, and yes, there should be a wire to top tail to ground the strings. Also, keep in mind that shielding only works if the conductive shield is wired to the ground as well.

Thanks for the reply.

I went through it and rewired where needed, still has the hum.

I'm curious how to hook up a wire to the bridge or tailpiece. There is really no where to run it. I suppose I could pop the wire under the bridge pickup holder, but it would look sort of hokey.

How can I ground the bridge otherwise (and not modify the guitar, i.e. not drilling any holes).

Gonna bump this old thread... hope someone can answer how to run a wire to the bridge in the les paul without modifying it.

Thanks - wag.

have you star grounded the guitar? ie, all grounds in the guitar go to one pot? ground loops cause hum. was the guitar equipped with active pickups when new? if not, it should have a bridge ground wire, whether it was severed when you 'hacked' into it or not is another story.

It isn't star grounded, which is something I could try. I recently shielded and star grounded my strat and it is whisper quiet for guitar w/single coils.

It had stock gibson humbuckers when it was new, with gold covers.

As I recall, it didn't have a ground wire coming from the bridge. There is no hole or access to the bridge at all in the guitar from the control cavity or the bridge pickup so I'm not sure how it could have ever had one.

It does have a screw on metal cover over all of the controls, so it is shielded.

Thanks for the reply.

You might look at http://www.guitarnuts.com/index.php. Lot's of tips on eliminating hums and noise.

Have you tried a different cord on it or put the guitar into a different amp?

just to be sure the problem is the guitar and not either a bad gound in the cord or the amp ? Not the first time this has happened .Or the amp starting to have problem ....

Have determined that the hum is from your guitar? Verify this, by plugging your guitar at a certain volume, pull the plug from your guitar. If the hum goes down, then it's your guitar with the hum. If the remains, it could be the cord or the amp. Now unplug the chord, if it disappears..it's a bad cord.

If it's your guitar and you said it quiets down when you touch the connected plug shield or quiets down when you touch any grounded metal on your guitar, it sounds be a reversed wiring on the PUP. Your body is like a capacitor and kills the hum. You can download a wiring diagram from Gibson's site and also websites for your PUPs. Is the hum quite noticeably loud? You can also check the capcitors in the guitar. You might have fried them when resoldering.

I am not sure how LP strings/bridge are grounded. My Gibson ES345 string are grounded...I checked with an ohm meter between the strings and the jack sheilding, and I don't know where it's grounded either.

All:

Thanks for info.

I've determined that the hum is from the guitar. Plugging my tele (shielded w/single coil sized humbuckers) into the same rig is whisper quiet.

The bridge and strings are definitely not grounded. I'm debating running a short length of black coated wire under the bridge pup and clamping it under the bridge.

The pups are wired correctly, I've confirmed that.

Thanks again for the info.

I realize I'm bumping a VERY old thread, but a Google search brought me here. Maybe the OP has since solved his problem, but I'll offer my opinions anyway, seeing as I'm experiencing the same problem right now and maybe it can help someone else.

Wagdog, you were getting that hum because you no longer had the metal pickup covers on. I have a 1980 Les Paul, and the LPs from that era used shield cans instead of a ground wire to the bridge. Meaning, along with the braided wire, every part of the circuit is encased in a metal enclosure -- the control cavity, the output jack....and the pickups. The metal pickup covers are part of the shielding. Take them off, and you create an opening in that shield.

Soon after I bought my guitar I put a set of Duncans in. The new pups were cool-looking and I wanted to keep the covers off, but there was tons of hum. I eventually figured out that I needed to put the covers back on to restore the proper shielding, and I did, and the hum went away.

I'm getting new pups again, and am faced with the following choice: Do I put the covers back on, or run a ground wire to the bridge and leave the covers off? Either will work...just a matter of how important looks are and if I want to make myself part of the grounding scheme.

Pull your treble side bridge post out. Drill a hole from the control cavity to the post hole. Run a wire thru this hole so it contacts the post and can be grounded to your volume pot that has all the other grounds (you do have all your grounds in one place, right?). Button it up and:rawk:

:facepalm:Forgot to mention: the threaded insert that the bridge post goes into needs to come out. You're grounding the string path by running the wire between it and the body.

I get the insert out using a block of wood with a piece of corrugated cardboard under it as a fulcrum. Then I pry it out using my wonderbar. A flat blade screwdriver with some length will work. Leave the post in for something to pry against.

This is what I ended up doing. Should have updated the thread long ago.

I got a big washer that had an inner hole that fit around the insert. I used a big socket and a threaded bolt with the same thread as the post. I put the socket onto the washer, threaded the insert and it came out with a little pressure. I drilled a very small diameter hole and threaded a piece of enamel wire through it and attached it to ground. I stripped the end that went in the hole with the insert, re-inserted the insert and post, and it works GREAT.

I didn't look at dates. I can't imagine any guitar not having a bridge ground. And this is a Gibby that came new that way!?!?

WTF were they thinking???

I do like the insert puller idea. I've always just used brute force and bull headedness.

I forgot to mention that I did put some felt under the washer. Probably not necessary, but I did it anyway.

I'd like to see a pic of this home made device. I seem to be stuck with a sideline repair bidness and anything I can do to save time is a plus.