acoustic - Unbroken String

Dr. John has collected this beautiful ES-125 (a Gibson Electric Spanish guitar with an MSRP of $125 back when it was produced) but it sounded as if it were underwater. Could the Unbrokenstring Crew toss it a life saver?

This instrument is in collectable condition, with all original hardware. The finish is finely-checked as you would expect a seventy-year-old musical instrument to be. A new hand-wound pickup was included in the instrument case, if the original one was defective and could not be easily fixed.

Years of oxidation and skin oil had made the neck sticky, particularly when the humidity is high (which is all the time in Houston.)

The sticky finish ends at the head stock, which implies that the finish is OK but the skin oil is the culprit.

Here, fine polishing compound is mixed with Dr. Duck’s Axe Wax to rub out the finish and remove the oxidation.

Next, we will look under the pick guard to investigate where the underwater sound is coming from.

This pick guard is shaped in such a way that it holds all the controls, and only a hole for the ground wire to the bridge and a slot to clear the pickup is needed in the sound board to electrify this instrument.

The ground wire to the strings appears to be a piece of lamp cord. The solder joint around the ground wire did not alloy to the ground wire between the pots, but slides up and down the wire.

This ceramic cap is the tone cap. It bleeds off high frequency to ground under the control of the tone pot.

This tone cap is marked 0.02uF at 50 volts.

On the capacitor tester, the value is correct.

However, the dielectric is very leaky, which would probably change things in the tone circuit for the worse. This is probably where the ‘underwater’ sound comes from!

Some high quality film capacitors are retrieved from stock.

These are the same value, 0.02uF, but are rated at 400v in case the guitarist plugs the instrument into a wall socket. At least the capacitor will survive. The player, not so much…

Dr. John lives about seventy miles away. As each change was made, a sound file of the instrument was emailed to him to monitor progress.

A free copy of ProTools First and Ableton Live came with the interface, which will amazingly run pretty well on this old rack-mount controller PC that I have on the bench.

John decided that the new pickup didn’t add anything to this fine old instrument, so it remains in its original condition as of seventy years ago (with a new tone cap, of course.)

Thanks for reading all the way to the end!

CONTACT – David Latchaw EE
281-636-8626

This wonderful instrument was rescued from an abandoned house. It sounded good acoustically, so the new owner asked if the Unbrokenstring Crew could repair the electronics and get it playable again? Let’s get to work!

This instrument is only a few years old, purchased and then cast aside.

An online source for specialty guitar parts had a 2018 model of the electronics. Can we make it work?

The mounting scheme uses four screws in the corners. Cleats will be added to the guitar so that the screws hold.

But the REAL advantage of the 2018 electronics is that the enclosure matches the curve of the body.

Common wood items such as yard sticks, tongue depressors, popsicle sticks, and paint stirrers are made from birch, the straight-grained ‘poor relation’ to maple. So the paint department lady at Home Depot gave me this stirrer.

Cleats to tightly hold the electronics in the body are fabricated by hand.

Next, the cleats are sanded to fit the curve of the body on the inside of the bout.

These are ready to trial-fit. The bevel on the corner, lower-left side, clears an internal brace in the guitar.

One shim goes here. Note the angled pieces, which will catch the screws in the electronics.

To protect the finish, low tack painter’s tape is used all around.

These clamps will hold the cleats in place as the hide glue sets up.

Both cleats are installed and the hide glue is curing.

Additional reinforcement is added in the corners to give the screws more material to grip. These bits will be in compression, so they don’t need to be super-strong, only tough.

Before we get too far, we need to do another trial fit.

I think we’re going to be good here!

I will pre-drill the holes where the screws will be installed. This should minimize splitting of the small cleats.

The actual drilling will be finger-powered, using this pin vise.

All four holes are pre-drilled.

Yes, I know. This isn’t terribly interesting.

The screws are installed. Not bad!

The jack plate holds the battery and has both 1/4th inch phone plug and balanced XLR connections. It was temporarily removed to give more access to the interior of the instrument. The new electronics hook right up to the jack plate.