Help-60 cycle hum

[rumplstratskin]

I recently installed new pups in my Epi LP. All was well for a couple of weeks then-out of the blue-I have a hum.
It is ground related I am sure but all the connections are tight and I can find no breaks in the wiring. The only thing that makes it stop is to push inward on the power cord plug which is approx. 1/32nd of an inch from being all the way in. I know the cord is good so I am left with the idea that the jack is bad.
Could this be it or is there another problem I have overlooked?

 

[59paul]

Re: Help-60 cycle hum

Take the Back Plate off, and look for the ground wire that comes in from the input jack. Carefully re-solder it back down . Then, look for the ground wire that comes in from the side of the cavity ( Body Ground ). Re-solder this wire back down to the volume pot. Dont solder it on top of your pickup grounds. Find a clean spot on the pot, and re-solder it there. This usually takes care of the hum. Get good , hot solder joints, and don't blow on them, this can add air pockets, which can make for a weak solder joint. You may want to use a little solder flux, to help get a nice, solid solder joint. If it still hums, carefully take out the input jack, and re-solder the connections on the jack. ....

 

[Artie]

Re: Help-60 cycle hum

The only thing that makes it stop is to push inward on the power cord plug which is approx. 1/32nd of an inch from being all the way in. I know the cord is good so I am left with the idea that the jack is bad.
Could this be it or is there another problem I have overlooked?

Are you refering to the plug that goes into the wall socket, or the cord that goes into the guitar?

It makes a huge difference on how to address this problem.

 

[rumplstratskin]

Re: Help-60 cycle hum

Found the body ground was a little loose. Re-soldered and made it nice and pretty. Now the hum is loud enough for me to be concerned about touching the metal parts of the guitar. Could the body ground have come loose inside the body or be otherwise compromised?

 

[Artie]

Re: Help-60 cycle hum

Hey rumpl; This is a bit hard to diagnose, partly because you're using some non-standard terminology.

In your first post, you refer to the "power cord". Generally that means the cord that goes from the amp to the wall socket. Do you mean the guitar cord instead?

In your last post, you refer to the "body" ground. To me, the "body" is the big wooden part of a guitar - which isn't grounded.

Generally, the input jack is grounded, the back of the pots, the bridge, and in some cases, a pickgaurd shield.

This sounds like one of those problems where a small meter would prove invaluable. If you don't have one, you may want to consider getting one.
Then, just double check all the "ground" connections inside the guitar. Recheck your wiring overall.

There really isn't any concern about getting shocked unless the amplifier itself has suffered some catastrophic failure. You can use the meter to check for voltage, both AC and DC, on the jack where you plug the guitar in.

Let us know to which of the above your refering to, and we should be able to lick this thing.

 

[rumplstratskin]

Re: Help-60 cycle hum

Actually I got the "body ground" term from 59paul. The power cord/inst. cable screw-up was indeed an improperly applied term. Sorry.

The wire in question comes into the cavity holding the control pots from the general direction of the bridge. It is a small, single filiment wire.

 

[59paul]

Re: Help-60 cycle hum

The " Body Ground " is the Bridge ground ( old School term...sorry ). Find a clean place on the pot, and re-solder it. It is either in this ground, or the one coming in from the input jack. You need to re-solder that Bridge ground 1st, and see if the hum goes away. Be patient, and get a good solder joint. This is a common thing, and I understood your question, I've had this happen many , many times. I doubt that you've broken any wires....so just trace the grounds. ....

 

[Artie]

Re: Help-60 cycle hum

The " Body Ground " is the Bridge ground ( old School term...sorry ).

Ah . . . well then maybe it is a standard term. Me bad. :smack:

I don't know if this will be of any help, but one of the things I find myself doing any time I open up the guitar to change something, like put in a new pickup or something, I replace the standard input jack with a stereo one. Then, just solder the ring and sleeve lugs together. This gives several "free" benefits:

1. It gives you twice as much "ground" connection on the input jack.
2. It gives you an actual connector, or "clip" to make the ground connection.
3. You have a "mute" position by simply pulling the cord out one "click".

Like I said, that probably doesn't help your problem per se.

 

[midnite_man]

Re: Help-60 cycle hum

Ah . . . well then maybe it is a standard term. Me bad. :smack:

I don't know if this will be of any help, but one of the things I find myself doing any time I open up the guitar to change something, like put in a new pickup or something, I replace the standard input jack with a stereo one. Then, just solder the ring and sleeve lugs together. This gives several "free" benefits:

1. It gives you twice as much "ground" connection on the input jack.
2. It gives you an actual connector, or "clip" to make the ground connection.
3. You have a "mute" position by simply pulling the cord out one "click".

Like I said, that probably doesn't help your problem per se.

Possibly not, Artie, but I just found it to be a great tip if you ask me. The fact that it provides better ground contact is enough reason right there to switch it out.
Thanks.

 

[59paul]

Re: Help-60 cycle hum

Artie, you very well could be right. It could be in the jack. It's definitely a ground problem somewhere. Could be that the ground has broken loose on the jack itself. I hate these grounding problems, but....usually a little patience pays off. Just have to trace em, and find the bad connection. It's a pain, but..it happens......

 

[Kent S.]

Re: Help-60 cycle hum

I a slightly related issue, have you tried a different cable? And yes some of the cheaper phone jacks will do wierd things like that ... sometimes it's just better to replace them with a switchcraft jack ... they are cheap enough, and last forever. I do like Art's stereo jack idea, as that also leaves open other mod possibilties down the road.

 

[Radeon]

Re: Help-60 cycle hum

Hey Kent, I have never heard of a switchcraft jack could you please describe it more for me. I would appreciate it and I like Arts stereo jack as well since you do get a bigger conneciton for the ground as well.

 

[rumplstratskin]

Re: Help-60 cycle hum

I a slightly related issue, have you tried a different cable? And yes some of the cheaper phone jacks will do wierd things like that ... sometimes it's just better to replace them with a switchcraft jack ... they are cheap enough, and last forever. I do like Art's stereo jack idea, as that also leaves open other mod possibilties down the road.

The cable is about the only thing eliminated at this point. It works fine with my Strat. Good idea though.

The jack in the LP is a stereo jack installed the first time I swapped the pups.

 

[rumplstratskin]

Re: Help-60 cycle hum

The jack is still my chief suspect. I will be running into town and buying a replacement today.

If that doesn't work I may just go ahead and pull everything out and re-wire the entire axe. Doesn't take that much longer and the only added expense would be the pots since I have everything but the jack on hand.

 

[Kent S.]

Re: Help-60 cycle hum

Hey Kent, I have never heard of a switchcraft jack could you please describe it more for me. I would appreciate it and I like Arts stereo jack as well since you do get a bigger conneciton for the ground as well.

Switchcraft is a company that makes switches,connectors and the like, they have only ben around for decades ... most Gibbies use Switchcraft switches and jacks ... there is nothing special about them, they are just made to a good tolerance ... I have seen some cheaper phone jacks that aren't machined well enough to keep a proper ground connection ... it happens.
Neutrik is another good brand of jack also. Seems to me though that that would be fairly easy to spot though, an intermittent contact type of thing, some cheap cables can have the ground or even tip section start to separate. Are you getting sound the entire time even with the hum, you may have to rebend the tip section of the jack if it's not making contact, although that doesn't sound exactly like your problem here. Off hand I'd say it's the jack, since you said it's a stereo jack ... some of the enclosed style jacks can screw up and their internal contacts can become loose causing similar problems. Again get a good brand of replacement.

 

[Kent S.]

Re: Help-60 cycle hum

The " Body Ground " is the Bridge ground ( old School term...sorry ).

No, no Art ... he means *your body* ground ... I just thought about that, and it makes a lot of sense actually ... and it's quite funny for some reason too... :laugh2:

 

[rumplstratskin]

Re: Help-60 cycle hum

There is no interruption of the sound off the strings. In fact if I hold the cable in in and hammer notes with my left hand the problem's solved.

I am leaning towards the jack being cause of the problem. I'll install it, resolder the "whatever-it-is" ground and we will see what we will see. thanks for all the advice and info. I'll get back toyou and let you know the outcome.

 

[Zeppelinfan8790]

Re: Help-60 cycle hum

I am eager to the outcome of your problem since I have the exact same problem with my Epi. I replaced the jack and it didn't solve anything, so I'll see if re-wiring the "whatever-it-is" ground solves the problem.

 

[rumplstratskin]

Re: Help-60 cycle hum

Well the new jack did the trick. The LP is rockin' with authority again!

If you replaced your jack and the ground inside is good maybe you could check and make sure you haven't reversed the leads to the jack.(I was just setting the iron down when I saw I had done just that!)

Again, Thanks everyone!

 

[Kent S.]

Re: Help-60 cycle hum

Well the new jack did the trick. The LP is rockin' with authority again!

If you replaced your jack and the ground inside is good maybe you could check and make sure you haven't reversed the leads to the jack.(I was just setting the iron down when I saw I had done just that!)

Again, Thanks everyone!

You did what? .... Oh no you didn't ... :smack: