Bad pot? Severe buzz when high....

[slodave]

Now that I got you to look... Back story, I built an electric guitar about 20 years ago with a single humbucker pickup at the bridge and one volume pot and one tone pot. Until two nights ago everything was wired/soldered as it has been for probably the 20 years. By the looks, I had rewired it, but not sure when.

There was always a hum when I lifted my fingers from the strings, went away as soon as I touched them. Originally, I forgot to ground the bridge, so I ran a black wire from under one of the nuts at the bridge to the pickup. I think that solved one ground issue, but the hum above hum never went away.... So, I decided to use the Internet, found a diagram to wire my guitar and went at it the other night. At first, I thought that only one of the pots was 500K (happened to be the tone and was clearly labeled). I did not notice a marking on the other pot (originally the volume) - last night I did, it's on the side and I can't really make it out, unless I take things apart.

I rewired everything, switching the tone and volume pots and also made changes to how it was originally wired, as it did not reflect the diagram I found. Hum remained, but disappeared when plugged into a portable Boss training monitor/line driver. Plugged into my amp tonight - was plugging into a Mbox mini the other nights (hum was present) and noticed that the guitar is completely quiet from 0 to about 4-5 on the volume knob (guitar), but as I turned up to 10, the hum came back, muted slightly if I touched the strings and really changed when the volume was at 10.

I also attached a wire to one of the strings as a test and made sure it was grounded, but the hum was still there, muting slightly when I touched the strings.

TIA!

Bad pots? Should I buy a new set and capacitor and start fresh?

[enzo1]

yes.... but I have no idea what i'm talking about cause..... bad pot and severe buzz....

[porsche4life]

Don't bogart bro!

[stuartj]

What you describe is a pretty good sign of a bad earth, or a sheilding problem.

Unlikely to be the cap, might be pots, although these last well. Hit them with some electrical contact cleaner, they could probably use it anyway after 20 years.

You can test the value of the vol pot with a multimeter. Its normal to use 500k with a HB pup, so if one is 500k, the other probably is too. The cap value should be .022, maybe .015.

Even HBs will produce a little hum and earth buzz. If its too much, and youre happy that the wiring is correct to the diagram youre using, youve got a dud/dry solder join somewhere, or a badly shielded piece of wiring.

Is the pup mounted to a guard, strat style, or mounted to the body, Gibson style?

[slodave]

One problem diagnosed... The original tone pot, now the volume, registers all over the place, with the highest reading at around 145K. It's bad. The original volume pot, now tone, registers from 16k to 490k.

The cap has a symbol like circle, 2A and 223K on it.

The pup is mounted ala Gibson.

Pots looks to be under $10. Might as well just replace them.

[stuartj]

Originally Posted by slodave

One problem diagnosed... The original tone pot, now the volume, registers all over the place, with the highest reading at around 145K. It's bad. The original volume pot, now tone, registers from 16k to 490k.

The cap has a symbol like circle, 2A and 223K on it.

The pup is mounted ala Gibson.

Pots looks to be under $10. Might as well just replace them.

Its a .0223 cap, so OK value. Nothing to go wrong there unless its a real old paper in oil type- these occasionally dry out. Its not the cap.

Could well be a pot- but before you replace, hit it with contact cleaner - or even some WD40 (its stuffed anyway). Sodering on pots can be difficult- you can cook them. Once cooked, good night. Could you have over heated it when rewiring?

If you do replace, use CTS 500k audio taper (not linear taper). Yep, about $10 each- be aware of long/short shaft length.

[WolfeMacleod]

Originally Posted by stuartj

Even HBs will produce a little hum and earth buzz. If its too much, and youre happy that the wiring is correct to the diagram youre using, youve got a dud/dry solder join somewhere, or a badly shielded piece of wiring.

If the coils are wound asymmetrical by about 10-15%. Humbucker will also not cancel out 120 cycle rectified current, if memory serves. Been a long time since I've read about that.
Ground loop issues will also cause hum.
As will bad pots.

If it's a 4-conductor 'bucker, is it wired correctly? Just had a go with a customer about that.. massive hum problems...blamed me. Didn't have it wired correctly...

[slodave]

I could have fried them 20 years ago while trying to get the solder to adhere to the pot. No contact cleaner, tried WD40, no love. The cap is one of the orange Chiclets looking ones. I'm more familiar with the electrolytic caps.

I'm inclined to just start fresh with the pots. A can of cleaner will cost about the same.

[WolfeMacleod]

Originally Posted by slodave

I could have fried them 20 years ago while trying to get the solder to adhere to the pot. No contact cleaner, tried WD40, no love. The cap is one of the orange Chiclets looking ones. I'm more familiar with the electrolytic caps.

I'm inclined to just start fresh with the pots. A can of cleaner will cost about the same.

Dave, call me tomorrow. Early afternoonish if you can. I've got some paper-in-oil caps.

[slodave]

This is the diagram I used.


Wiring from my pup has the same coloring, including a bare wire. Today, I know how to solder correctly, 20 years ago, not so much...

I did notice tonight, that if I pinch (grab it) the hot lead (it's not a bare wire) from the plug jack to the volume pot, that the hum/buzz really goes off.

[slodave]

Wolfe, I'm now inclined to say that this pup is a Seymour Duncan, but it does not have that name on the top. Right now, I don't have a spare set of strings, so I'd rather not take the strings off to pull the pup out.

I'll give a call in the afternoon.

[stuartj]

Wolfe is a hexpert, he will sort you.

BTW- not all pickups mfrs use the same wiring colour codes. It may be that your running only one coil and the hum is 60cycle single coil hum.

At least youve only got one pup to trouble shoot- its usually the combintion of two thats the problem.

[slodave]

Aw, screw it. Clipped the strings, I'll grab some more tomorrow... Lets see if there are markings on the pup.

[slodave]

It's a SD.

EDIT: If the little sticker is correct, it's a JB model from about 1990.

[slodave]

Sooo....

Found a couple 500k mini pots. I was afraid I'd have to venture into Hollywood, which is no fun in the rain.

Looks like I hacked the pup many moons ago. when I pulled the pup wire out, I found a loose wire that had been taped into the pup line. I also had removed a section of the shielding. Removed that wire, added some shielding, added shrink wrap on top of that.

Wired the pots according to the diagram, testing the pots over and over. I also installed the bridge ground wire correctly now. All back together and there still is a hum, but not as bad. Reacts the same way though. Touch the strings and it's quiet.

Now the problem is that I seem to have no tone! The pot is okay, spinning it does nothing to change the tone. Last night, the range went from very bright to very warm and muddy. Now it seems to be 50/50.

Wolfe is going to send a couple of capacitors, so I might live with things as is for the moment.

On the upside, I remounted the bridge at an angle, it was straight across before, so now the intonation is good all the way through 2 octaves - I have a full two octave neck.

[Shuie]

Originally Posted by slodave

Touch the strings and it's quiet.

^ Ground.

[slodave]

I agree that it's a ground issue. Am I reading too much into it though?

Additional info I noticed. I have yet to plug back into an amp, but I did plug into the Mbox mini and listened via headphones. I touched the Mbox itself, which happens to be metal and the hum goes away - so obviously a ground issue. My laptop - which the Mbox is plugged into, does not shock me in any way, but I know the pwr supply is a two prong, not a more conventional three prong (ground). It's possible that the wiring in my place is not grounded properly, but I remember testing that a year or so ago and things were okay.

[WolfeMacleod]

Originally Posted by slodave

.... but I know the pwr supply is a two prong, not a more conventional three prong (ground). It's possible that the wiring in my place is not grounded properly, but I remember testing that a year or so ago and things were okay.

Dave, in all seriousness, be F'ING CAREFUL when messing aroud with two-prong amps thingies. I;ve been hit before havign one plugged in backwards and touching another piece of gear.

Normal for hum to go away when touching the strings, even with humbuckers. That doe tell me that your wiring is grounded OK. Maybe the humbucker just picks up a little hum. Some do....
Didja look up 120 cycle hum yet?

[slodave]

I may have to play with this...

If its offensive, it can be reduced by using cavity shielding and shielded wire, but its a bit tricky, and you have to make sure you don't create ground loops. When I did my first Les Paul, I used the old style wire with the braided steel cover and grounded it in about 4 different places. IT was awful, much worse than before.

I noticed that when the electronics (pots) are near my body or if I hold the guitar away from me and put my hand near the electronics, the buzz increases. Other than that, I think it's the normal hum.

EDIT: I'm not going to rewire my current guitar with shielded wires, just try and shield the cavity.

....Now about that tone pot.

RE: Power supply - I was referring to my laptop, the Mbox is powered via USB. Just thinking that if the laptop power supply was a 3 prong, maybe it would help...

[sammyg2]

Best way to get rid of 60 cycle hum is to move to Europe.