Piezo in an Electromatic Center Block Jr...

GlenP

Country Gent
Jul 23, 2019
2,465
WA
Of course all the prewired cables are color coded and all my shielded cable is black. So when I replace those wires, so I can stretch things out and mount them where I want, I might keep a short portion of the unshielded wires at the end to help identify them, but I hate to add two extra solder joints in each wire that is not really needed. Have to think about that. maybe I can use some sharpie or paint pens to color code my black shielded cables. I may keep the prewired short leads on the Control X board side only, I don’t want to solder on there any more than I have to. The jack and switch have lugs that are easier to work with, and I am replacing both of those pre-wired chrome parts from the kit with gold parts that I bought separately. The only soldering required on the board are easy access through holes near the corner for the piezo signal and shield wires (X-Bridge wires in the figure below). I am not going to remove any of those other wires from the board, but maybe cut a good length where I can strip off a portion and solder that to my shielded cables.

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GlenP

Country Gent
Jul 23, 2019
2,465
WA
I have been finishing up a TV stand project in the garage and practicing for a performance coming up on Sat at a local Farmers Market, acoustic stuff, so not much time to work on this the past couple of weekends. I will post some updates when I make some more progress.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
Not much activity lately, just been a heat wave here and I have been avoiding the garage. I did some continuity checks on my replacement gold mini toggle 3 position DPDT switch for the Mag/Both/Pie selector to make sure that I will orient it the same way as the pre-wired switch. It has a face label side that matches the other switch and they are consistent with each other. Just wanted to make sure the closed circuit poles match the appropriate switch positions on my replacement part as the original.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
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Sorry to leave this hanging for a while, I just had to finish another project in the garage to free up some space. This is part one of a modular entertainment cabinet. Nice to get these boards put together finally and off the workbench. So, hopefully the weather will remain more conducive to working in the garage. Here is my tv cart project, phase one. I need to stop starting new projects before I finish another project.
 
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GlenP

Country Gent
Jul 23, 2019
2,465
WA
I had an afternoon free to work on this in the garage today. Next step is wiring the 6 individual saddle signals and shields to the summing board output signal and ground. Though not necessary, I arranged the wires in saddle order from low E to high E, then the summed shielded hot piezo signal wire on the far right. Some pictures of the process are below. I did continuity checks along the way after each saddle wire was soldered to verify good signal and ground paths.

first wire is the output wire, other end goes into the Control-X circuit board and blend pot.
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high-E string ready for soldering next, and so on, to the low-E...
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an insulating sticker goes over the signal wire ends, then a copper shield sticker goes over top of that and is grounded. done.
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GlenP

Country Gent
Jul 23, 2019
2,465
WA
5FC4DB11-7FC0-4088-8C00-0D31D3E91565.jpeg E0772DE2-188C-47E7-B1BF-EECF52F4B0AE.jpeg I made a kind of “pick guard” layout to mount the pots and switch so I can wire things up in their relative positions to make the new harness. Top view and bottom view. I need to pay close attention to the available paths through the pickup routs to make sure I have enough wire to route the parts through.
 

drmilktruck

I Bleed Orange
May 17, 2009
19,776
Plymouth, MN
Glen, it's cool to see this taking shape.

BTW, yesterday, I saw that Schecter has a C-1 E/A (piezo & mag), and I mention it because they gave it controls that give tone and volume control for both the piezo and mag pickups. Also they have a toggle switch for combining the piezo and mag pickups, instead of a blend knob like my PRS has. If I didn't already have the PRS, I would have pulled the trigger. Even so, I like the mag/piezo combo so much that I had to fight the urge to get one. The thing that saved me is that they are now on back order just like the PRS was.

Here's a pic of how it's set up.

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I had one of those several years ago. Fairly good sounding piezo and mixed signals. Heavy guitar though.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
Great progress so far!

Thanks! I was worried about the little summing board PCB, the surface signal and ground patches were kind of close together, but I was able to get them all wired without any shorts. The rest is just typical guitar wiring, pickups, pots, switches, jacks. The few remaining wires that go into the PCB preamp/pot are through-holes, so should be a bit easier than those little surface mount patches.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
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The magnetic pickup blend pot will be wired such that you have full neck at the start, both at the middle detent, and full bridge at the end, as you roll clockwise, ie like turning up a Vol pot.
These are also called MN taper pots or panner pots.

from the StewMac website:
https://www.stewmac.com/video-and-i...-and-electronics-and-wiring/blend-pot-wiring/
the neck will be source B and the bridge will be source A.

Since the neck and bridge go through different routs, I will have to wire one pickup to the harness, then wire the other after pulling the blend pot out to the other’s access point. Probably will stuff everything through the neck rout and wire the bridge pick up last.

The blended mag output goes to the Mag/Pie DPDT selector switch.
 
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GlenP

Country Gent
Jul 23, 2019
2,465
WA
A1A423E4-6C62-4455-A214-C242D93D8351.jpeg Before I start wiring everything I made a test installation of the Control-X pot/preamp board, and it was a good thing I did. This can fit, but only a certain way, and that requires me to rotate the board once it is in position so that the board faces the output jack hole so I can access the trim pot and phase switch. I realize that I will need plenty of extra slack in the wires to install and rotate that one. At one point the board rotated corner to corner and got stuck in the guitar, but I was able to get it loose by pushing a corner free with a dowel through the open jack access. Another helpful idea will be to put the battery access nearby that area on the back of the guitar. The square switched stereo jack is just a bit too large to fit through the existing round jack hole, but I can ease out the corners with a sanding stick so I can feed the jack out with a bit of extra wire to make the piezo trim pot adjustments on the preamp board. Once everything is wired up and put together. I can just remove the jack plate pull the jack out slightly to access the preamp trim pot.

For size comparison, here is a stock vol pot, the blend pot, and the controlX board. Also the stock jack and the stereo switched jack.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
I am reusing some of the insulated wire that I pulled from the two mag pickup volume pots to take the signal from the blend pot to the mag/pie switch. The middle lugs are for the pickup conductors, top for bridge, bottom for neck. I may wait to connect the pickups until I test install the harness, since those are kind of bulky, and I might just wire them at the very last, just pulling the blend pot out the bridge pickup cavity. Here you can see the opposite corners connected for ground and the blended output signal. The white wire is the center conductor and the black is the shield connected to ground. I kind of cooked the insulation a bit on this one in a couple of spots.

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the blend pot will replace the original three position switch and the individual neck and bridge vol pots, the neck/bridge blended signal wire goes to the new 3 position DPDT mag/pie switch.
 
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GlenP

Country Gent
Jul 23, 2019
2,465
WA
C0B42E11-CE4E-4B25-B834-29A17A5C1C3B.jpeg The rest is more of the typical guitar wiring, I have some of the stock shielded wire that I will re-use for some of the new connections. I have the magnetic pickup half of the DPDT switch wired, and now have a couple of wires to connect to the Control-X piezo board that interrupt the piezo signal wire on the other half of the DPDT Mag/Pie switch. The pre-wired switch just used shorter lengths of single conductor wire, but since I have to route this a much longer distance from the lower bout to the upper bout under the neck pickup, I will be using shielded wire and will ground the shields.
 
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GlenP

Country Gent
Jul 23, 2019
2,465
WA
D32F082B-A8C7-45C4-BCA5-E9901A1A7602.jpeg I made some more progress this weekend. I got the stereo switched jack wired up with enough extra wire length to pull it out of the body a bit and access the piezo preamp trim pot. (This is possible because the larger hole is covered up by a football jack plate, @thunder58 would approve). I did continuity checks of the tip and ring and the battery interrupt switch, everything looks like it is connected right. I still have a few wires to attach to the preamp board itself, these are through holes so should not be too hard.

the prewired jack had white for the ring and red for the tip. Since I was reusing the white wire from the original master tone to the tip, left, I wrapped a bit of red tape on it as a reminder to match the instructions. Also, the typical breakout convention is Right, Ring, Return is Red, so I used a red wire for the ring connection, for the optional stereo piezo isolated signal. But I wrapped a bit of white tape to match how it was preWired in the instructions to help keep track of where to connect that to the board. Clear as mud, I guess. They were just using a red wire for the tip/left mono output, and I thought that it made more sense to use a red wire for the right channel on the ring. The black is ground and the yellow is the battery interrupt switch wire, to turn off the preamp when the jack is unplugged.
 
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Runamok

Country Gent
I had a Ghost piezo system put into a Warmoth Starcaster body. Less complicated than the Baggs system but not all the features. Turned out well. Good luck with your project. The guy who did my work said if there hadn’t been access from the back he might not have agreed to do it. He had no interest in fishing things through the f holes.
I dunno. I once saw a sailing ship inside a bottle.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
I finished all the wiring that I can do outside of the guitar. I need to do a few guitar modifications before installing the harness. I need to fill and redrill the 3 pos switch hole to make it smaller. I have to drill a small dia hole for the stereo/mono pop-up switch button on the preamp board next to the piezo volume pot. And I need to install a battery access door on the back.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
E9B87250-9A4D-4320-ABC6-00D393B32DF9.jpeg I had to sand down the layer of paint in the original hole to get to bare wood, then my 0.5” dowel needed a layer of paper to shim it snug to fill the spot where the three position pick up selector switch once was. My new switch plate will cover up the dowel, and a new smaller hole will get drilled here for the new mini toggle after the Titebond quick & thick wood glue fully dries.
 

GlenP

Country Gent
Jul 23, 2019
2,465
WA
I drilled the small hole next to the piezo pot for the push button stereo/mono pop up switch. I got a bit of paint chipping even though I had put down some masking tape before drilling. It is not too bad, I can try to touch it up. But this small dia hole will not have a washer or anything to cover up that edge. I should have started with a smaller dia pilot hole, that might have helped. I can add a small countersink to clean that up, but will have to do that carefully to not make it worse. I need like a chamfered bit made from fine grain sandpaper.
 
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GlenP

Country Gent
Jul 23, 2019
2,465
WA
original hole filled and drilled:
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test installation of chrome mini toggle and plate, the gold one is wired into the harness, just not ready for that installation yet.
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chipped off some paint at the edges
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which will be exposed by the pop-up button switch
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I made a little sandpaper cone and used a drill bit to spin by hand to help countersink the hole...
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just took my time and carefully sanded down the countersink by spinning the drill bit by hand with gentle pressure and 400 grit paper until the countersink edge covered up the chipped paint.
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With the hole edge cleaned up I can touch that edge up with a paint pen, either white or black. A mismatch in the color won't be as noticeable on the countersink edge, since it will always have a slight shadow to it anyway. A black contrast might look good also, the switch comes with both a black plastic tip and a white plastic tip. I have not decided which one I will use yet. That is just about the right amount of countersink for a finger tip to activate the pop up switch when it is fully down in mono mode to activate stereo mode.
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such a relief that I was able to get a clean edge after those chipped paint spots showed up. I can almost leave it like it is with a bit of the wood showing there. But, it should be easy to go over that exposed wood with either a black or white paint pen, or like a cream color to match the binding.

That is enough work for today. I need to be well rested and think about cutting open the back for the battery compartment. I will try to find a spot that won't be in the way of the jack or the pots and mark it out on the back. Then drill small pilot holes around the outline of the hole, getting them closer and closer, then cut in between the holes with a key-hole saw. I can sand the edges down with a sanding stick. Luckily the battery door has a good sized lip that will cover up the hole edges, so paint chipping should not be as much of an issue. Crazy enough it just might work!
 
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