This offset-waist project guitar is playable and is actually very cool. The owner had ‘gotten in over his head’ and broken a few screws and buggered a few others. Could the Unbrokenstring Crew whip this instrument into shape again?
The easy part is to install gold Gibson speed knobs on the controls. There are a lot of good parts in this instrument.
Looking more closely, the neck pocket will need some serious attention. What’s going on here?
This is what’s going on. If you look at the high and low strings, you will see that they are not the same distance from the edge of the fret board. This neck is not lined up with the body of the guitar.
It is easy to remove the truss rod cover because these screw heads are already sheared off.
The heads of the screws around this pickup were mangled to the point that a regular Phillips screw driver would not engage them anymore. Here we’re using a pair of cutters to twist the screw out while a magnet serves as a sentinel to keep pieces of metal that will inevitably shave off the screw head away from the magnet in the neck pickup.
Wow these are long. These go most of the way through the body.
We are still working on this one. This is really tough.
Note that the head is chewed up pretty badly. New screws are already in stock.
No springs or tubing are underneath this pickup, bur rather a chunk of too-thick too-hard foam.
Now we know where this body came from!
And the neck is from Guitar Fetish. Here, I marked where the body ends with a dotted line. More on this later.
So what can we do about these broken screws?
No problems removing the tuners… these screws were busted off as well.
To remove the broken screws, we apply heat to the body of the screw. This dries out the surrounding wood so that it shrinks slightly.
I used the same technique with the wire cutters to grasp the body of the broken screw to twist it out easily.
Rinse and repeat for the remaining broken screws.
Now that everything is apart, I need to fix this neck pocket. First, we get the bottom flat.
Then we get the sides flat. This body was painted after it left the factory, so we have plenty of over-spray in the neck pocket that we need to clear out with this scraper.
I believe that we are down to real wood again.
Acoustic coupling occurs best when the neck and body fit tightly, ‘bone on bone,’ if possible. I really like this wood hardener, which is essentially solid Lexan dissolved in a light solvent.
This raw wood will take a few coats to seal and harden.
As the old cowboy on the cattle drive once said, “Be sure to look back to see if the herd is still behind you.” Periodic fit checks are always a good idea.
This neck is beautiful because of the thick layer(s) of polyurethane finish. However, the polyurethane layer may get in the way of acoustically coupling the neck to the body. Here, I’m hatching the area where I will scrape away finish.
Again, the luthiers’ scraper is the perfect tool for removing finish evenly and smoothly, leaving the surface exactly flat.
That is much better! Not shown: the finish on the end and sides of the neck where it meets the body is also removed.
A pin vise holds the proper-sized twist drill to resize these holes for the Correct pickup screws.
A little canned air clears out the cuttings from the holes.
Over-sized screws held the pick guard in place. The Correct screws are smaller. Here, a small dowel is glued into each hole, which will be re-drilled with the proper-sized hole. This is hide glue shown here; just fine for this duty.
Once the hide glue is cured, each dowel is trimmed flush.
I jumped ahead to show how the Correct screws are nearly flush with the top of the pick guard. Almost factory.
This single-coil pickup reads as an open circuit. That tiny wire is broken.
The tiny wire is broken because these black and white leads can twist around. Hot-glue now holds them stationary.
The pickup is working now. Here is some new, softer foam in place to hold the pickup in position. Leo Fender would have used short pieces of vinyl tubing on the screws to act as a spring, but these covers go all the way to the bottom of the cavity route, so the foam is the best option for this setup. Oh, and you can’t see it, but the copper pulled out when the original foam was replaced, so this guitar has copper in the pickup route and under the pick guard.
Here is the actual pickup.
And here is the separate cover.
The Correct screws are not nearly as hard to drive as the other screws.
More Guitar Fetish goodness! The metal parts of the guitar should be tied to a single point, not at various places along the signal path. This soldered wire ties the metal body of the pickup to one side of the audio path, and has got to go.
That connection is now cut open.
A separate layer of foil is wired to the single point ground. The connection to the bridge and strings is accomplished with another sheet of foil and this outside-star lock washer. Again, the mechanical ground is not part of the signal path.
Everything goes together as it should. See how the star washer makes the connection between the bridge and foil?
The Correct controls are marked T for tone and V for volume. The switch is ready to wire.
The new wiring is accomplished with solid wire in Teflon tubing. The pickup wiring is the vintage ‘push-back’ wire, which is actually really easy to use and can be very clean-looking as the insulation is cut without resorting to wire strippers.
When the control plate is in the correct position, new holes are bored for the screws.
The neck plate needs some attention. This metal polishing paste is also what I use to polish fret wire.
These holes are reamed to the proper size for the Correct screws.
The tuners are going on! A bit of red felt is glued to the face of the socket so that the finish is not marred.
These new screws going into the correctly-sized holes are very well-behaved now.
The truss rod cover screws will now live in properly-sized holes as well. The pin vise is getting a workout today!
The customer uses these strings. We need the guitar strung so that we can get the neck straight.
Note that the outside E strings are equidistant from the edge of the fret board. The screws attaching the neck to the body are tightened at this point.
Now that the neck is properly positioned, we can finish the setup. The truss rod is adjusted to make the neck perfectly straight. Do you see the slip of paper next to fret 9? It is used as a feeler to see that the ruler is in contact with the fret board all along the neck. A piece of paper is about 0.0015 inch thick or so. It is used to check for fit between every fret on the fret board. Yes, that makes a difference!
This neck is brand new, and so the frets had never been leveled. Just a tiny bit of sanding was all it took.
Here I am taking a measurement of fret wire height. I need this shortly to file the nut slots.
Frets are polished.
Fret board is cleaned and conditioned with oil.
Here we are cutting the nut slots to depth (about 0.006 inch plus the fret wire height measurement made earlier.)
Once the nut slots are at the right depth, the rest of the nut is sanded away to make the slots shallow. We need to sand a little bit more away near the high E and B strings, and maybe next to the D string. We’re getting there!
The instrument is back together and sounding good!
This is a closeup of the saddle barrels. These are factory intonated and are VERY close to correct. How do they do that?
Our patient is making her debut at the studio.
First Note.
I think he likes it!
Thanks for reading all the way to the end!
CONTACT – David Latchaw EE
281-636-8626
The AutoMix function that Peavey developed has been discussed elsewhere in the blog. Lots of EQ knobs here!
Note the graphical EQ and bi-amp capability.
Woah! An Instrument System! Ooh. Aah.
On the rear panel is the power switch and speaker connections.
Peavey mixes and matches front panels (inputs, preamp, eq) and rear panels (ps, power amp) to build different heads.
Name, rank, and serial number, please.
The blue circuit board at the top is for connections to the power transistors. The I/O connections are to the left and the power supply filter caps are seen here.
More blue boards at the top, for power transistors. Driver transistors are found on the square heat sinks. Do you see the problem yet?
This circuitry is all preamp and tone circuitry.
This sucker got HOT!
The worst damage was to components that were near the root cause. They burned because the transistor on the aluminum heat sink suffered an internal short circuit.
The heat of the electrical fault was high enough to melt solder, which happens around 650 deg. F.
A matched set of driver transistors were installed and the circuit board cleaned. The destroyed components to the right have been removed and will be replaced.
The new parts are mounted just above the circuit board. We can get flame-proof resistors now, unlike when the unit was built with in the 1970s.
More collateral damage was found on one of the blue boards. This solder trace acted as a fuse at its narrowest point.
The circuit board is now cleaned up and the gap is bridged with a bit of 16awg solid copper wire.
Some of the power transistors were shorted as well, so all of them are now replaced with a matched set of eight.
These parts are still made by ON Semiconductor, the heir apparent to the Motorola semiconductor product line.
The electronics are back together. The filter capacitors are original, but are still in great shape, so they remain in service.
And, of course, after all the components and circuit boards are in flames, the fuse finally does its job. Of course.
With a new fuse, the electronics are connected again and initial tests begin!
This unit is back on the air! This unit is almost hifi sound quality, with endless bottom end. Good Job Peavey!