PRS SE Hollowbody Piezo - making some improvements

[Joe Garfield]

I got this guitar in October. It’s a PRS SE, made in China in PRS’s acoustic factory. It’s a full hollowbody, built like an acoustic, and very light and resonant. It’s very, very nice, but there are things that remind you pretty quickly that it’s not a USA made guitar. But no complaints from me - I didn’t pay for a USA made guitar!

That pic is from the website but is of my actual guitar. I’m having trouble posting pics but you’ll soon see what it really looks like when it wakes up in the morning

It has laminated maple top and back, with a veneer on top and back, and even on the insides. The inside isn’t painted or stained, but once I saw the flame figuring inside I was happy! Mahogany sides and ebony fretboard. All the binding is done in real flamed maple. It also has really beautiful Abalone bird inlays.

The only thing I’ve done to it so far is install PRS locking tuners, and a set of locking bridge posts. More details will come as I highlight things I’ve found or what I’m changing.

Anyway, I never really liked using the volume control as the tone would cut out way too quickly. I also got some odd ‘fuzz’ from time to time - I wasn’t sure where it was coming from, but now I have an idea: a cold solder joint on the tone capacitor. The pickup selector switch stopped working, and I noticed a bunch of corrosion on two of the potentiometer washers. It’s my only complete guitar, but that was enough to investigate.

[Joe Garfield]

Here’s a pic of what the corroded washer left behind. It was not easy to clean that up! I tried rubbing gently with vinegar but it just wasn’t working. So I scraped it off, which of course left some minor blemishes around the hole. I cleaned that up with some automotive ‘scratch and swirl remover.’ Now it looks like it should.

Before:


After:

[Joe Garfield]

Before I got this guitar, I was in the process of building a few kits. For one of those kits I somehow talked myself into buying a set of PRS 58/07 pickups. So of course it’s been on the back of my mind those pups should go in the PRS guitar! With all this stuff on my mind, I decided to gut the whole electric/electronic system. It has a Piezo pickup system, which is mechanical vibrating saddles wired to a tiny pc board under the bridge, then into a larger PCB inside the guitar. It sounds like a very realistic acoustic guitar when played through a full-range speaker. The guitar has the ability to play just the Piezo, a blend of Piezo and magnetic pickups through the same cable, or hook up two cables for two independent channels.

This is what everything looks like:

[Joe Garfield]

And here’s the guitar completely gutted:

[Joe Garfield]

So it’s getting the new pickups, all new CTS/Dimarzio potentiometers, including a push-pull pot for (partial) coil splitting, a 'treble bleed' capacitor, and a Switchcraft switch. I live on an island so I had to order parts and am waiting for them; hopefully they’ll be there this weekend.

It was hard to find an appropriate 25K pot with fine knurling for the Piezo (it’s an active system with a battery, so lower impedance and hence the lower pot value.) So I ordered an amplifier pot - basically the same but with a solid shaft - and will switch the resistor wafers between that and another CTS pot.

Interestingly, two pots are from Alpha and the Piezo pot from China, but they all have 3/8” shafts so I won’t need to enlarge the holes to fit CTS.

I also ordered custom black plastic pickup rings, but they won’t be here for ~5 weeks. I'm also considering buying a set of flamed maple pickup rings, or maybe making a set out of hardwood or plywood and a flamed maple veneer.

So that’s where we’re at: the guitar and I are patiently awaiting parts - well, trying to be patient! Hopefully they’ll be here Saturday.

[Joe Garfield]

I received parts today. I swapped the shafts between two pots so I could retain original resistance value and use all matching shafts and knobs. One pot is a CTS 25k solid shaft, one is 500k knurled shaft. I needed 25k (fine) knurled. I could have swapped the resistor itself, or any combination of parts, just wanted to use the brass bushing and retain the proper value stamped on the case.

Both pots are new CTS to replace the import no-name branded pot.

[Joe Garfield]

[Cliff Rogers]

Sauce? 🤔

[DrNomis_44]

Occasionally, I'll pull-apart a pot in order to fix it and restore normal operation, which reminds me of some work I did on a mates Wampler Euphoria pedal, basically all the controls on the pedal worked normally except the gain control, even when maxxed-out it didn't produce as much gain/overdrive as it should have, I spent some time going-over the pedal and finally found the cause of the low-gain, turns out that some kind of contamination got into the pot and caused a partial short-circuit from the wiper to one side of the carbon resistance track, the pot was a 1M log if my memory serves me right, when I measured it with a multimeter it was about 4.7k when the shaft was rotated fully clockwize....definitely not right, to fix it I used my sharp craft-knife to gently scrape between the inner wiper contact and the carbon track, when I measured the pot after re-assembling it, I got normal resistance readings again, so I soldered the pot back onto the circuit board and then re-assembled the pedal, the pedal then functioned normally with plenty of gain.

[Joe Garfield]

Sauce? 🤔

Sauce on a steak like that is like running a vintage tube amp through a modeler.