PRS McCarty 594 Ground Issue(?)

[Brianiac5150]

My 594 seems to have developed a ground issue and - as I'm a complete electronics newb - I'm uncertain what needs done.

It's not always done this and I first started noticing a clicking sound as my hand moved along the neck when playing. Not unlike that discussed in a GENERAL DISCUSSION thread titled, "Noise touching frets." I thought it might've been the cable or 'amp' I was plugged into, however, have tried several with similar results. The buzz also lessens/goes away when touching the bridge or tailpiece.

This past weekend I took the back plates off and used an Allen key to touch a few things and see if it changed. Sure enough it did. I made a video which can be seen by searching "PRS McCarty 594 Ground Issue" on YouTube. In this video, I'm plugged directly into a Fender Blues Jr.

I'd post links to the referenced thread and video; however - also a forum newb, I've not reached my 3 post minimum. ;-)

I found the wiring diagram via the PRS site and things LOOK correct, however, I'm uncertain.

Any advice, guidance or assistance will be greatly appreciated.

 

[andy474x]

The 594’s (and many other PRS models) have unshielded control cavities, which is the most likely culprit. I recently got a 594 and noticed the same thing, and have noticed it on other PRS guitars in the past, too.

More than likely, your 594 has always been this way, you’re just now noticing it. Perhaps if you changed your playing environment/location, or just if there is something new in your space or area, contributing added RF that the guitar is picking up.

When I looked into it, I found that apparently PRS doesn’t shield the cavities because it subtly rolls off the top end of the tone. Personally, I’d like a shielded cavity, but... yeah. It is what it is.

 

[Lacire]

Just a guess without actually seeing the guitar. But if its not inherent in the circuit as andy474x stated and you’re just noticing it and the wiring looks good inside, try moving just your guitar cable where it goes into the guitar jack, don’t touch the 1/4” cable plug or anything on the guitar and see if the nose changes, if so it’s the jack. If not, you may have a cold solder joint somewhere in the grounding. Do you have a soldering iron and can you solder? If so, go through your wiring diagram and reheat/remelt each ground connection starting with the guitars input jack. If you don’t solder you’ll have to take it to somebody.

 

[Alnus Rubra]

Don’t know if this is your YT video

Putting this up, if it’s any help?

 

[Brianiac5150]

Thanks! It is not my video, however, is exactly what mine does.
Maybe this’ll now post:

 

[Nice F Holes]

Does the hum get louder or softer when you turn the volume pot?

 

[Brianiac5150]

Does the hum get louder or softer when you turn the volume pot?

Gets quieter as the volume knobs (either) are turned down and has a different tone around 5-6.

 

[Nice F Holes]

I think that means the noise is emi (electromagnetic interference) - in other words, your guitar is picking up noise from the environment, and it's not a ground issue. It gets quiet when you touch it because you're giving the signal an alternate path to ground. Generally they say, if you touch your guitar and it DOESNT get quieter, then you have a problem.

Your guitar has shielded signal wire so my guess is it's more likely coming in through your pickups.

I guess you could try touching each of the individual braided steel shields with the allen wrench, and see if there are any that do NOT cause the sound to go away when touching - that would indicate the shield is not connected. However I think this is probably unlikely...just my hunch. I'm not an 'expert' in this by any means, but I'm an engineer who plays guitar and is building a few kit guitars, so I'm not entirely guessing here.

 

[Nice F Holes]

Oh, I just watched the part where you touch the pickup selector switch. Just to confirm, can you touch the very center part of the switch with the wrench - the part that like 1/8" thick metal running front to back?

 

[RickP]

I had a Strat that did this and found the ground wire from the cavity to the bridge had come loose. Soldered it back and the noise went away. I have no idea if the 594 is grounded in this way, but thought to mention it just in case.

 

[Nice F Holes]

I had a Strat that did this and found the ground wire from the cavity to the bridge had come loose. Soldered it back and the noise went away. I have no idea if the 594 is grounded in this way, but thought to mention it just in case.

If a loose bridge ground was the case, then touching the strings or bridge would have no effect on the noise. To test, you could temporarily touch a wire up to any part of the bridge or strings, and the other end any other metal part of the guitar. If that solves the problem its a loose bridge ground wire. If nothing changes, it's something else.

 

[Brianiac5150]

Oh, I just watched the part where you touch the pickup selector switch. Just to confirm, can you touch the very center part of the switch with the wrench - the part that like 1/8" thick metal running front to back?

Yeah...I didn't touch that part in the video, did I? I just tested this, though, and it does make the hum go away.

 

[Brianiac5150]

If a loose bridge ground was the case, then touching the strings or bridge would have no effect on the noise. To test, you could temporarily touch a wire up to any part of the bridge or strings, and the other end any other metal part of the guitar. If that solves the problem its a loose bridge ground wire. If nothing changes, it's something else.

This is, essentially, what I'm doing in touching the metal parts within the wiring. When not putzing around in the control cavities things are the same as the other video above. If anything metal on the front of the guitar is touched it reduces or goes away. Grabbing a tuning machine head really makes it go away the most. Gone really. Holding the tailpiece, bridge or pickup covers reduces it, but not completely gone.

I thought it might be a loose wire, too, but everything feels really tight in the cavities.

 

[aphantomvaper]

I will concur...the guitar strings bridge to headstock are acting like an antennae and picking up EMF from your environment. Try moving around while the guitar is plugged in and holding it, point the head stock in different directions, without touching any metal on the guitar.

If the hum varies it's just the nature of a non shielded guitar, and you will have to touch it if you want to play it.