The Unbrokenstring Crew is amazed at the tough life that this tweed Fender Blues Junior has endured. Yes, it doesn’t work at all. Can we bring this poor thing back to life?
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Brian salvaged this amp from the curb in front of a house in North Carolina while volunteering in the cleanup following Hurricane Florence in 2018.
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Water damage is clearly evident on the tweed fabric, with stains and mold inside and out. The glue holding the fabric on the amp has failed, particularly on the bottom half of the cabinet.
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Starting from the bottom up, we use hide glue to stick everything back down. The lacquer coating on the tweed fabric has saved it from completely disintegrating.
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We are employing hide glue because it is not water based; we don’t want to make the wood cabinet swell any more than it already has. The hide glue can be easily cleaned up afterward, even after it dries, with warm water and a rag.
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Here, we’re removing the chassis. Fortunately, the rust is not too bad on this chassis.
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Someone has been here before, and they probably didn’t have a Fender employee badge.
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Too much heat and rework has destroyed the plated-thru holes in the circuit board. We can repair this.
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The connections (called ‘nets’ in circuit board parlance) are restored with small bits of stranded copper wire, tinned and soldered in place.
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The heart of any tube amplifier is the output transformer. It bridges the gap between high voltage power, tubes, and the loudspeaker. This HiPot (high potential tester) is measuring a complete failure of the insulation between the primary plate circuit windings of the output transformer and the secondary loudspeaker windings. Surprisingly, the loudspeaker is fine!
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Hidden on the back side of the chassis, the output transformer has lived. And Died. Alone. In The Dark.
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Fortunately, The Unbrokenstring Crew has a supply of original parts for boutique Fender amplifiers and clones, from Texas Amplification stock. This nice example of original Fender iron fits perfectly on this chassis.
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Testing the 6BQ5 / EL84 tubes, on the other hand, produces a light show. The purple glow is ionized gas inside the tube, and the blue lights hitting the paper behind the tube are beams of uncontrolled electrons.
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The red filaments are the only colors that should be there. After these pictures were taken, I had to replace the socket adapter on my TV-7U tester because it melted internally. The rest of the tester is fine and was re-calibrated – with a new socket adapter.
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After the light show from testing the tubes, each section of the amplifier is tested separately, in order to discover any other collateral damage from either the water or the failed output transformer. This amp will be Good To Go once the glue dries!
The original neck on this MIM Black Strat was made from wood that tended to twist when the string tension varied, either because of temperature changes or when employing different string gauges. It’s now time to take this guitar to the next level, and make it an iconic Blackout Strat
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The neck will be retired to another instrument.
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This instrument was built in 2006, which happened to be the 60th anniversary of the founding of Fender Corporation.
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The neck is off and headed to its new home.
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David Gilmour’s Blackout Strat has a maple fret board. This instrument will get a new maple neck, with a 59 ‘C’ contour and an almost 2 inch wide nut. With light strings, this guitar will feel like a nylon-stringed classical guitar.
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The aftermarket Fender tuners are lined up with the machinist’s rule and tightened into place one by one.
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These tuners are ‘locking’ tuners, which positively grip the end of each string in a clamp. This is necessary on this instrument because of the very light gauge strings we will be using.
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Head stock and nut are ready to go.
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The middle pickup appears to be not working. Let’s take a look inside.
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Sure enough, there is a broken wire inside the pickup cover.
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The break in the wire is literally in the very last turn! So one turn is un-spooled and threaded through the eyelet where it belongs.
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As was done at the factory, the wire end is pulled through the eyelet a few times and soldered in place.
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The middle pickup is tested and is right where it should be.
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The Classic(al) Blackout Strat is strung with 7 gauge strings; Yes, not 12s, not 10s, but with Billy Gibbon’s own Dunlop Reverend Willy Extra Light Electric Guitar Strings, .007-.038. With the proper setup, this instrument has the play-ability and feel of a nylon-strung classical guitar. Thus, we have the Classic(al) Blackout Strat.
Texas Amplification, operated by the late Darryl Shifflett, built some of the finest Fender Blackface clones available. Much of the inventory of Texas Amplification was subjected to the flood waters of Hurricane Harvey. This newly-completed combo amp was high enough to escape immersion, but did not escape the subsequent rain, humidity and condensation. Could the Unbrokenstring Crew make this new unit like-new again for its new owner?
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The nickel plated feet and corner hardware are new, but a light coating of rust from the screws has leached onto the hardware. The Tolex covering appears to be unaffected by the water.
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Here’s a close-up of the rust. Not a big deal, but this triggers my OCDC (like obsessive-compulsive disease with a bit of AC/DC tossed into the mix.)
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The back panels of the amp are held on with the Correct screws, but they are showing signs of iron rust as well.
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This back panel is plywood. It had been wet but had been slowly drying out and was no longer warped. Surprisingly, the Tolex covering was still glued in place.
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This bit of Tolex covering, however, had become unglued.
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The Jensen loudspeaker was high and dry, but we’ll check it for any damage.
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The loudspeaker is more-easily inspected by removing the baffle board.
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With the baffle board out, it’s easy to verify that everything is in good shape.
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More importantly, no apparent water damage had occurred here! The Unbrokenstring Crew is fairly certain that this amplifier was at least partially submerged at the height of the flooding. This loudspeaker and grille cloth appear unaffected!
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Rust Biox is a tool of the museum curator. When old objects are carefully cleaned and restored for display in a museum, such as old weapons or other artifacts, Rust Biox slowly removes iron rust while preserving the un-oxidized material under the rust. This was once sold in the United States as an automotive rust remover, but did not become a ‘hit’ and was removed from the market. The Unbrokenstring Crew, however, is just cool enough to have a source.
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After each item is processed with Rust Biox, a water rinse and hot air dry prepares it for re-use.
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The feet of the unit are nickel-plated steel over a rubber bushing. Here, the bushing is separated from the metal foot for processing.
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These screws hold the feet onto the bottom of the amplifier cabinet.
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The metal feet are restored. Next, the Rust Biox will remove the rust stains from the rubber feet.
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Interestingly, this line may have been the ‘high water mark’ and so this unit could have been partially submerged. Furniture polish will clean and condition the Tolex covering to like-new condition.
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Heat from the hot air pencil softens the Tolex adhesive. The hot Tolex is pressed into place and allowed to cool.
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The hot air pencil has done the trick! This cabinet appears to have never been wet.
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The electronics are brand new, with no signs of water damage or corrosion.
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The Fender Vibro Champ is a single-ended Class A design, a low-parts-count, simple-to-build amplifier with surprising response and tone.
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All magnetics used in Texas Amplification products are procured through Mercury Magnetics. Top-of-the-line!
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The violet jewel in the pilot light tells us that we are ready for business!
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All back together, this amp is running a four-hour-long burn-in to verify that it is 100%. …And dry out anything still wet. This unit was delivered to its new owner, who promptly placed it in his recording studio.
The fuse blew in this Sunn Stinger 20, but the new fuse blew as well. Then, it quit working for good. Cool Under Fire wanted this combo amp back in action. Could The Unbrokenstring Crew sort it all out?
Our patient still has that cool Sunn vibe after all these years, even if it doesn’t work. That name badge is recognized by all.
Getting up close and personal to the front panel, we see an input jack and three tone controls.
Independent Gain and Volume controls show that this unit means business! The mute button and headphone jack give this amp a family-friendly advantage over other inexpensive practice amps.
As is found on many guitar amps, the cabinet is sealed with a closed back.
Oh no! The sticker says “DO NOT OPEN.” What are we going to do?
We open it, of course. How long has it been since you’ve seen a loudspeaker with a square magnet?
Obviously this is a four-ohm loudspeaker.
The steel chassis has circuit boards for the preamp functions, just behind the controls, and power supply and audio power amplifier at the rear of the unit. Nothing appears out of order here. No, wait! Look here!
This wire has come un-crimped from the terminal, seen in the background.
We can just open this terminal up a bit, re-insert the wire, and solder it in place. But the question remains: Could this have been the reason that the unit blew fuses before it finally quit permanently? I don’t think so.
While we’re waiting on a copy of the Sunn Service Bulletins for this amp to come via email, let’s take a minute to clean this unit up.
The controls hold the front edge of the circuit board in place, and a couple of screws hold the back edge steady.
The headphone jack is entirely isolated from the chassis of the unit. Even though the chassis is wired to the green wire safety ground in the AC cord, taking measures such as this makes the UL Certification easier.
The input jack is shielded from interference with this metal bracket. This kind of additional shielding is almost never done on inexpensive amps… this Sunn is definitely a Cut Above!
The switches and controls are easily cleaned now that they are easily accessible, as shown here. The Unbrokenstring Crew NEVER forces cleaning fluid around the shaft of the potentiometers as a cleaning procedure, because dirt and old lubricant is forced inside the control. It cannot end well. Sorry, StewMac.
With all the hardware out of the way, it is a trivial matter to clean up the face plate. Gibson Guitar Pump Polish is pressed into service for this step.
Reassembly also involves tightening the woodwork. Over time, wood shrinks (even in humid South Texas) so most amplifier cabinets will develop buzzes and rattles as they age.
Maybe if we work quickly, the “Do Not Remove” police will not catch up to us and put us in jail.
The Service Literature arrived! It states that the next-higher ampacity of fuse should be used in this unit; There was an error at the factory wherein units in this serial number range had an inadequate fuse installed! This little amp has run for hours with no issues!
Dr. Shoen’s girlfriend at the time found this microphone in a dumpster behind a church. What did he really find, and could it be more than a theatrical prop onstage? The Unbrokenstring Crew goes to work!
Shure Brothers built this iconic microphone at the factory in Evanston, Illinois in the years between 1951 and 1961. The art deco design is recognized around the world as “The Elvis Microphone.”
The 55S is a smaller version of the Model 55 Shure Brothers microphone first produced in 1939.
Unidyne is a term coined to reflect that a single (unitary) microphone diaphragm is employed. The moving coil technique employed to convert sound pressure into electricity makes this a dynamic microphone; Thus we have the word “Unidyne.”
Units with the ON/OFF switch were produced after 1961
The silk wind screen is badly deteriorated. The microphone makes a loud ‘clunk’ noise when it is moved. We need to look inside.
Four screws allow the halves of the microphone body to be separated.
Inside the microphone, we see the element at the top and a multiple-impedance transformer on the bottom.
Two screws hold a bracket that retains a foam vibration dampener in place, which has long since deteriorated and crumbled away. This is the source of our ‘thunk.’
Two more foam vibration dampeners hold the bottom of the element. They are also deteriorated. More ‘thunk.’
The microphone element lifts out easily once the top bracket is removed.
Some of the foam isolation dampeners remain on the bottom two microphone element supports. These are end-of-life and no longer available from Shure.
It is easy to see places where the silk wind screen is missing.
The matching transformer is mounted along with a couple of boxes that retain the now-deteriorated foam vibration dampeners.
Two screws hold these parts in place.
We see the back side of the impedance selector switch in the background, and some set screws in the foreground. What do these do?
The bottom set screw is supposed to hold this spring sheath around the green and orange wires in place.
The top set screw holds the impedance selector switch in place.
We need to take everything out.
The spring sheath runs through the base of the microphone and protects the wires as the microphone is flexed at the joint.
Inside the top of the microphone case we find this sticker, which records the patent numbers employed in the design of this microphone.
The pivot between the microphone and base needs to come apart for cleaning and adjustment.
This screw can be adjusted to set the stiffness of the microphone head relative to the base.
Graphite washers ride between the moving parts for lubrication.
A dent in the body of the microphone needs to be removed. Yes, I’m using my luthier’s hammer to pound out the dent.
Can you see where the dent was?
The old silk wind screen was glued inside the case of the microphone.
Acetone will dissolve the old glue. It will also dissolve silk, turning this cleanup step into a blue sticky ‘hot mess.’
But a little patience and perseverance yields a clean microphone case.
Warning – Skeleton Shot! I’ll betcha that you have never seen a microphone like this.
We found some sheer blue silk fabric for the wind screen. This brighter blue is not historically correct, as ‘Victoria Blue’ (Pantone 2756) was specified by the factory. However, this blue matches the Shure nameplate and badge.
This is a test.
Fabric is glued to the top and bottom as well as sides of the front half of the microphone enclosure. We will now fabricate a soft pillow to allow the fabric to be ‘blocked’ into place as the glue dries in the front half of the microphone enclosure.
This soft pillow will be fabricated from Oomoo. Yes, the silicon mold-making resin will be just the thing.
Equal parts by volume are mixed.
The mix is poured into the front half of the microphone. A plastic sheet protects the microphone shell from the casting material. The Oomoo silicone mold material won’t hurt the microphone shell, but I don’t want to risk contaminating the microphone shell and possibly compromising the glue adhesion later.
And here is our pillow!
We don’t want the pillow to deform the fabric, so these high points are removed by hand with an Exacto knife.
Here is the finished pillow inside the microphone shell.
And here is the fabric, glued and blocked into the microphone shell.
Time to reassemble. The moving joint is reassembled and the cable from the base to the enclosure is reinstalled.
The spring around the cable is held in place with the set screw, as we discovered earlier. This is a nice view of the fabric in the back shell of the microphone. This piece is just a flat rectangular sheet stretched across the back, so it’s easy to glue in place by hand without a block.
The joint is back together. No lubrication is necessary as the graphite washers are doing their job.
A smooth, firm grip at the joint is established before installing the lock nut.
This is what the spring protecting the wires is supposed to look like.
The microphone element works, but I couldn’t resist taking a look at the technology behind US Patent 2,237,298. The hemispherical shell on the back of the element helps establish the cardioid pickup pattern of the element.
I fabricated new foam vibration dampeners, which are installed in three places. The matching transformer assembly goes back where it belongs.
The microphone element is reinstalled where it belongs and wired in. This is now a working microphone. The covering on the microphone element is actually the same material used for vintage silk stockings a.k.a. nylons.
A set of four matching screws are fitted and finished to hold the two halves of the microphone enclosure together.
