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HELP! Getting loud hum from my PRS after pickup change!


Firebrand

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so you narrowed it down to the pot, and if it is a grounding issue, it is between the pups and the pot. forgive me but my knowledge of passive pickups is rather elementary, but i understand that they do have a polarity, could they be out of phase?

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I don't think the noise is an out of phase issue. The tech obviously didn't clean the back of the pots as already stated. I found a small piece of green scotchbrite with some rubbing alcohol, followed by more of the alcohol on a paper towel will get them clean enough to take solder. Your "pro" tech cooked the damn thang with too much heat. Fix it, take it back and tell them you're mad as hell and want a refund. At least a partial one. Tell them you don't have time to do it yourself and that's why you had him do it in the first place.

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I don't think the noise is an out of phase issue. The tech obviously didn't clean the back of the pots as already stated. I found a small piece of green scotchbrite with some rubbing alcohol, followed by more of the alcohol on a paper towel will get them clean enough to take solder. Your "pro" tech cooked the damn thang with too much heat. Fix it, take it back and tell them you're mad as hell and want a refund. At least a partial one. Tell them you don't have time to do it yourself and that's why you had him do it in the first place.

 

 

The spot that's getting the solder should be scored whether or not there is any kind of coating on the pot casing. Solder does not stick well to smooth surfaces.

 

I just zoomed in on the pics for a closer look, they scale up quite well. After zooming in on them I can see that all the solder joints are {censored} with a capital {censored}. You should take it back to the tech who butchered it and demand your money back. I'd also try to get something to compensate for the month that it was in the shop being butchered. If that guy is backlogged up to a month it's most likely because he's fixing all his other {censored}-ups.

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FWIW, I did clip that straggling little wire found in pics 2 and 4 that was pointed out.

and, yeah, I am really disappointed that the tech didn't take time to find out if there were any other problems before calling the job done.

The other thing I found laughable was he told me he made the pups non-coil tap because "it sounded awful", but after prodding and poking around I realized that they still are tap-able via the push/pull on the tone.

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Please read!

 

Something many people do not understand is that the inside magnetic polarities of the two pickups must be the same or the magnetic fields will be weakened and increased hum can be the result. The simplest / best way to be 100% sure this is the case is with a compass.

 

Now I am not saying this is the case with yours, nor am I saying that there are no other problems such as ensuring that all grounds go to only one common point (star grounding).

 

I do agree from what I can tell that the solder joints are poor.

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Chummer!

Please tell me more about this compass test.

 

As for another viable A/B;

I realized I had one other guitar to test the noise level against, it having a similar wiring.

My daughter's Daisy Rock Isis.

Sure enough it has 1/4 of the noise floor until I pull up the coil tap.

Ordering a Bourn volume pot. Might as well get the good stuff. And only $9 for 2 on eBay.

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If he followed the McCarty Wiring diagram, they would be tappable.

 

 

Initially he said that is what he did, followed by the statement of him not liking the sound of the pickups tapped.

Maybe he thought about doing it while taking a break and never did. Doesn't matter (that much).

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Initially he said that is what he did, followed by the statement of him not liking the sound of the pickups tapped.

Maybe he thought about doing it while taking a break and never did. Doesn't matter (that much).

 

 

Did you get your money back yet? That's the only thing I would discuss with him.

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$50? Hell, I'd do that for a friend for free and you bet your ass it would work too.

 

 

I don't think the noise is an out of phase issue. The tech obviously didn't clean the back of the pots as already stated. I found a small piece of green scotchbrite with some rubbing alcohol, followed by more of the alcohol on a paper towel will get them clean enough to take solder. Your "pro" tech cooked the damn thang with too much heat. Fix it, take it back and tell them you're mad as hell and want a refund. At least a partial one. Tell them you don't have time to do it yourself and that's why you had him do it in the first place.

Or you can just scratch it with a flathead screwdriver.

 

Yeah that grounding wire doesn't look right. There should be a pool of solder with the wire sitting at least partially inside of it.

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In pic #5 there is a single strand of wire that looks like it comes from that twisted bit of braided shielding and crosses the lug of the red wire on the right. Is that strand of wire still there? That will cause the problem you are having for sure if that wire is indeed connected to that braided shield and making contact with the lug to the right.

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$50? Hell, I'd do that for a friend for free and you bet your ass it would work too.


Or you can just scratch it with a flathead screwdriver.


Yeah that grounding wire doesn't look right. There should be a pool of solder with the wire sitting at least partially inside of it.

 

Or sandpaper works well too. Equally important (and I'm sure most know this but it hasn't been mentioned) is to use a nice fat tip on the soldering iron for the backs of the pots. You really need that extra heat dissipation to get the solder flowing. Using a pencil tip is a surefire way to struggle way more than you need to for a good joint on the back of the pot.

 

I found this out the hard way. I got lazy on my last project on the last few joints and used a pencil tip for the back of the pot (I only have one soldering iron :facepalm:). They seemed fine at first but as soon as I tried to pull them through the body cavity, it was on my Casino :facepalm::facepalm:, they broke off. I had to pull everything back out to resolder them and it was a lot of extra work that could have been avoided if I wasn't trying to "save time" by not swapping tips :facepalm::facepalm::facepalm:.

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Chummer!

Please tell me more about this compass test.


As for another viable A/B;

I realized I had one other guitar to test the noise level against, it having a similar wiring.

My daughter's Daisy Rock Isis.

Sure enough it has 1/4 of the noise floor until I pull up the coil tap.

Ordering a Bourn volume pot. Might as well get the good stuff. And only $9 for 2 on eBay.

Sure, the closet inside edges of the TWO humbuckers must have the same magnetic polarity and the compass would point the same way over the closet pole pieces when properly oriented...I am not simply talking about the two rows of pole pieces as found on each humbucker...the outside pole pieces of the two pickups do not play any part in this test.

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  • 3 months later...
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The him saga has finally been solved today. After taking the guitar up north and having the neck refinned I decided to take soldering into my own hands. The wiring was not even close to the McCarty diagram on the PRS site. So after 45 minutes of carefully unsoldering, cleaning and resoldering the guitar sounds amazing. Both black wires from the Dragon IIs were run to ground, when lack from the bridge is actually hot. Add to it the wires that would have been taped off for no tap were the ones run to the tone pot. Wow. Time to go to work and make some $$$.

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