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what is causing hum ?


Ted S

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Hey folks, new guy here :wave: . I have an old El Degas that generates a constant hum though the amp. I'm sure it's not the amp or cable as I don't get any hum from my Arai. I've cleaned the pots and jack, and there isn't any static or pops from the pots when turning. Any ideas ? It's all original with recent strings.

 

thanks in advance.

 

Ted

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Ok, thanks guys. Let me repeat what I understand you to be saying. The bridge should be grounded inside the body. I'm assuming a quick test without taking stuff apart would be to clip a jumper from the bridge to the output jack casing ?
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Would anyone have a pdf of a generic schematic ? Just something I could familiarize myself with. My Degas is a LP copy.

 

OOh OOh, while I am at it, here is another question.. Axe #2, Arai Pro II, hollow body electric, If I am on the bottom pickup I get nothing unless the volume on the top pick is just hardly turned up from zero, then all is good.

 

Both my guitars have pretty much sat for 20 years and I have recently picked it back up and started taking lessons to get back on track.

 

thanks for your patience All.

 

Ted

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Originally posted by Ted S:

Ok, thanks guys. Let me repeat what I understand you to be saying. The bridge should be grounded inside the body. I'm assuming a quick test without taking stuff apart would be to clip a jumper from the bridge to the output jack casing ?

Wow! You have killer problem solving skills. I am impressed. Yes that will do Tom. I didn't even think of that.

 

Does the other guitar have a pup slector switch? I have heard of some circuits that act that way.

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Originally posted by Big Red 67:

Wow! You have killer problem solving skills. I am impressed. Yes that will do Tom. I didn't even think of that.

 

Does the other guitar have a pup slector switch? I have heard of some circuits that act that way. [/QB]

Thanks BigRed, the only switch on #2(Arai) is the regular top/bottom/both.

 

Ted

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Ok, regarding Degas and hum, no changes what so ever with a jumper or not, hum is constant, not huge, but there. It sound's like a sheilding issue perhaps ?

 

Arai and funky switch, my previous description of the symptoms were a little off, it's more like this.. either one or the other p/u selected all is normal, with both selected (switch in middle) treble p/u volume down to zero, rythm turned up, get nothing until treble volume is just cracked.

 

Make any sense to anyone ?

 

thanks

 

Ted

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Everyone has something to contribute. You'd be surprised at things you may think are common knowledge among players that turn out to be little known facts. You may very well have some gems the rest of us can glean when the appropriate question or comment arises. :thu:

 

These guys with oodles of tube amp knowledge blow my mind. I've owned SS amps my entire life. Someday soon I hope to own a cool, little Class A, ~5 -15 watt amp.

It's easiest to find me on Facebook. Neil Bergman

 

Soundclick

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Minor update, I got back into the pot section and added some sheilding (read tin foil) as a test. Didn't want to yank the pups out yet. It was a shot in the dark with no effect. I did notice that it is only being generated by the treble pup when the tone pot is opened up. Any thoughts ? Maybe when I get some time I could make a project and replace all the guts. Any suggestions on hardware ? It was my first electric 26 years ago. I saved up ~~ $200 at the time. It's a decent axe made in Japan, fits well and feels good but I wouldn't want to sink a rediculous amount of coin at it. Your comments sure would be appreciated.

 

thanks

 

Ted

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Try using an ohmmeter between the bridge and the back of the volume pot as well as other ground points inside the cavity (output jack threads, etc). If everything is connected correctly you should read zero ohms.

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I did the checks as you suggested Has-Sound, my grounds are continuous at a few ohms. I did notice tonight that depending on where I position myself relative to my amp, the hum almost disappears. It's not feed back, volume is low. Gone completely if the pots are closed up. My Aria doesn't display anything like this under the same conditions. I'm thinking poor shielding or bleeding caps ? What do you think ? All original 25 year old harware.
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Hum is usually bad caps, in a amp or guitar.

 

Hum can also be a mismatched output set or loss of one tube in an output set.

 

I would grab a different guitar and plug it into the amp if you have not done this just to truly isolate that it is not the amp.

 

Since movement of the guitar though, does change things, this is probably a shielding issue.

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I've tried with my other guitar, no symptoms, amp and cable prove to be good. I just spoke with a buddy who also plays and happens to be a bit of an electrical/electronic guru (makes my head hurt sometimes!) he suggeted that it is possible that one coil in one of the pups may have opened up (humbucker not bucking). I'll check and post later. Thank again for all the responses. I'll get to the source sooner or later.
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Ok, I would like to thank everyone for their patience in putting up with new guys questions.

I was at my instructors with "alleged" humming guitar, guess what, quiet as a church moose, yes I said moose. Got thinking, hey numbnuts (me) you're practising beside a freaking 53" TV, ya think that might be giving off some EMI :rolleyes: ? Drag my gear into a "clean" room, no problemo....... what a knob I am, I was about to replace the pups ad re-wire everything.

 

Thanks again :thu:

 

Ted

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