Breedlove 12 String Breaks Strings

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I saw Leo Kottke in concert on a Thursday evening in 1975.  The next day, I gave up on the guitar solely because I felt so overwhelmed by his talent and felt unworthy to ever touch a guitar again. Confronting my sick, twisted fears from that traumatic experience included resuming my music studies thirty-five years later.  Doing her part to attack my illness, my Darling Bride, who went with me on that fateful night, purchased this Korean-made Breedlove Stage Concert guitar for me.

In standard tuning, the high G string broke more often than not. What to do?  I started by re-chamfer and polishing the edge of the hole in the tuner where the string passes.  The breaks appear to occur when the G string passes across the hole in the tuner.  When the string passes across the hole, a stress concentration could occur right at the chamfer.

 

Here is a bit copied out of my Breedlove’s Owners Manual.  The stock high G string is 0.008 inch.

 

These came from Strings By Mail. Many individual strings can be purchased ala-carte from them.

 

My plan is to throw conventional wisdom to the wind and add enough string to the post so that the portion of the string leaving the post only touches the round portion of the post, not the hole nor its chamfer.  Here, I am measuring the broken string to establish where the stress concentration occurred.

 

Then I added the length of the string that was broken off, then estimated the circumference of the hourglass-shaped tuning post and multiplied times 12.  The plan is to get enough static string on the post to cover the hole, preventing the portion of the string leaving the post on a tangent from getting anywhere near the hole.  Putting more than three or four wraps of string around a tuning post is generally frowned on, because the more string wound on the post, the longer it takes for the tuning to stabilize.  We’ll see…

 

I love the bridge on my Breedlove.  I don’t have to reach inside the guitar to push the bridge pegs out nor verify that the ball ends are up against the peg and bottom of the sound board..

 

The ala-carte strings have ball ends that do not necessarily match the color codes used in the sets.  Who would notice??

 

I polished and chamfered the hole edge to the best of my ability.

 

To keep the loose string end under control while fiddling with the length of the new string, I put my classical guitar capo across the neck to corral the G string.

 

Here’s the G string.  I can grab it, pull it, handle it, measure it, trim it, pull it, and it won’t get away from me.

 

I estimated the additional string length in a previous step, and am adding it here.

 

We have all been here.  Wish me luck!

 

Here is eleven turns of the G string around the post.  Uh oh.  I am a little short of covering the hole.

 

But, tuned up to pitch, the portion of the string that tangentially leaves the tuning post is no where near the hole.

 

Here is another view, showing the smooth transition from the last wrap.  I don’t think we will see the sharp bend in the portion of the string that leaves the tuning post tangentially that would occur if the guitar were tuned and the string were bent over the edge of the hole in the tuner.

My original goal was to load up the tuning post with enough string to cover the hole entirely, thus eliminating the chance that the portion of the string leaving on a tangent toward the nut would experience a sharp bend across the tuning post hole.  But, I lucked out this time, and now the string is no where near the hole.  Thus, I could have reduced the number of turns of string on the post.  Not too bad for my first investigation.

I have not broken the high G string on my 12 string guitar since these pictures were taken.  The high G string has stayed in tune while playing and does not appear to de-tune between sessions any more so than the other strings.

Thanks for reading all the way to the bottom!

CONTACT – David Latchaw EE
281-636-8626

Peavey Deuce Combo Amp Refurbish

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WARNING – A very long blog post awaits you. Typical guitar amplifiers can be described in terms of functional blocks – power supply, preamplifier, power amplifier, and loudspeakers. This refurbishment effort left NONE of those blocks untouched. Sit back and enjoy!

This Peavey needed some work before it could be added to David’s tonal arsenal.

 

I removed the chassis for inspection.  This is the ‘clean’ channel.  The LEDs illuminate to show channel selection.

 

The ‘effects’ channel has a little more tonal control.

 

This unit uses an odd solid state phase shifter scheme and a mechanical reverb unit.  The standby switch is on the front, and the power switch is on the back.  The Fender switch scheme for tube amplifiers sometimes puts both switches in the back, and of course, I always select the wrong one because I have to reach around where I can’t see to work the switch.

 

Somehow, the 8 ohm jack is open-circuit.  We will need to look at this on the inside of the chassis.

 

This is the main power switch.  The ‘ON/ON’ function allows the user to capacitively couple the chassis to one side of the AC line.  This sometimes helps with hum reduction, although the three wire AC cord defeats one side of the switch.

 

The fuse is intact insofar as the red pilot light turns on when power is applied.

 

However, this 10A fuse is the wrong part.  Someone has been jacking with this amp!

 

Sorry, this needs to be fixed.

 

Note that the scratches on the tube base indicate that the tube was inserted incorrectly.  How can this be?

 

This is how.  The guide posts were broken off.

 

The reverb tank bag is screwed down to the bottom of the unit.

 

Everything here is intact, no damage, transducers are OK.  We’ll set this aside in a safe place for now.

 

We found the first bug.  Poor little spider.

 

All of the high voltage capacitors show signs of venting.  See the little bump in the black rubber, next to the 350?

 

The output jacks on the rear of the chassis have been damaged.

 

The pin contact has been bent all the way out so that the plug cannot touch it.

 

This pic is to document that these inside star washers should be placed between the jack and the chassis.

 

Both jacks shall be replaced with new ones.

 

All new hardware was used, of course.

 

The jacks are wired together and the jacks are wired directly to the output transformer.

 

The amplifier circuit board has seen some significant pyrolysis.  Maybe this happened when the tubes were installed the wrong direction, because of the missing guide posts?

 

To remove the amplifier circuit board, the tube socket pins must be unsoldered and the wires removed.

 

With a little attention to detail, the circuit board comes off the tube sockets.

 

This is the underside of the amplifier circuit board.  I wonder if someone poked the wires a little too far, so that the ends touched the chassis?

 

This printed circuit board will be rebuild, and all the components will be moved to the solder side of the board.

 

Lots of rosin flux was used to clean off all the solder.  Lots of alcohol is used to clean off all the rosin flux.

 

The rag gives some place for the mess to go.

 

With the circuit board cleaned up, we can see if it can be repaired.  It’s too old to replace; Peavey has no stock.

 

The carbon tracks are removed.  The remaining copper is trimmed back to where it is still attached to the laminate core.

 

Comparing the circuit board to the layout, we can verify where the traces and components actually should go.

 

Both sides of the circuit board are now spotless.

 

The new components will be placed above the surface of the board to allow for cooling and to insulate each part from the live circuit traces below each component.

 

The copper around the mounting hole is gone, so the lead of this component will be sweat soldered to the surviving trace.

 

To bridge the gaps in the copper, bare solid wire will be soldered in place, and insulated from the rest of the circuit with this Teflon tubing.

 

Here is a picture of the Teflon tubing at work.

 

All of the components are installed now.  The Peavey Deuce uses four 6L6 tubes but only had two screen resistors; the other screens were tied to the plate voltage.  The Peavey Mace amp uses six 6L6 tubes and has six screen resistors.  I went with four screen resistors, as I believe that using two was an engineering oversight.  The original Peavey documentation was ambiguous on this point.

 

This is a nice side view of all the components, flying above the printed circuit board.

 

Subsequent testing showed that the original phenolic tube sockets were either contaminated or were carbon tracked.  The old sockets need to be replaced.  Here, we’re drilling out the pop rivets that hold the sockets onto the chassis.  Note the magnet, which attracts the steel shavings and keeps the mess to a minimum.

 

These tubes hang base side up, thus the base clamps keep the tubes firmly in the socket.  As we know, heat rises, so the sockets get hot during normal operation.  These were cooked.

 

The new sockets will be held in with #8 stainless fasteners.  Here, the chassis holes are enlarged to pass a #8 machine screw.

 

Likewise, the holes in the new ceramic sockets need to be enlarged to the same extent.

 

The sockets will be mounted from the chassis.  We won’t have any access to the bottom of the socket once the printed circuit board is soldered onto the socket pins, so I need some captive hardware permanently mounted to the socket ears.

 

These small outline nuts are brass with a silver plating.  They solder easily to the ears of the new tube sockets.

 

Once the nuts were tacked into position, a nice fillet of solder is run all around the nut to keep them in place.

 

These new ceramic sockets are ready to be tacked into place on the circuit board.  Pay attention to the direction of the index slot!

 

Here are the new ceramic sockets in place on the refurbished amplifier circuit assembly.

 

The new sockets and tube clamps were installed with the stainless steel hardware. To assure that the solder joints under the sockets will not be under stress during operation, a spare octal base tube is plugged into the socket to align the socket contacts before each solder joint on the amplifier pc board is made.

 

Here is the refurbished amplifier circuit board assembly in its final resting place.

 

All the high voltage power wiring, filament wires, and signal wires are in place and ready to be dressed.

 

The power supply circuit board had many bad parts.  The large square resistor seen here was open-circuit!

 

And, when that large resistor died, it got really hot!

 

These large round flameproof resistors are available online as a better-than-factory replacement.

 

Nearly every component on this assembly was replaced.

 

We have 488 volts DC with no load on this assembly.  That will be acceptable.

 

The power supply board is back in place, and the cabling dressed.

 

On the preamplifier board, many of the electrolytic capacitors were showing their age.  The one of the left vented.

 

To remove the preamp board, all the knobs come off (of course.)

 

The felt glued on the face of this socket protect the faceplate from damage.

 

The preamp board is free from its moorings.

 

There appears to be little wrong on this side of the board assembly.  There are no signs of prior repairs here.

 

The vented electrolyte from this electrolytic capacitor attacked the copper lead of this capacitor and ate through it.

 

These cement resistors were bad.

 

The new resistors were mounted off the face of the board, to improve reliability.

 

The controls were flushed, dried, and re-lubricated.

 

This hybrid amp uses solid state techniques for low-level amplification and tubes for high level amplification.  These two transistors were bad.  These driver transistors are part of the phase splitter circuit, and drive the tubes directly.  The replacement transistors have a different pin-out, so the circuit board holes were marked with the correct layout.

 

Some components in the phase shifter circuit were changed out to improve its performance.

 

Here’s one of the original loudspeakers.  Car audio?

 

The other loudspeaker was mildly interesting.  Unfortunately, it was completely destroyed internally and was scrapped.

 

The old loudspeakers were removed and the cabinet was cleared out.

 

The customer selected a pair of import Celestions.  These were modified for an eight-bolt mounting pattern.

 

A magnet was employed to keep the steel shavings away from the loudspeaker magnet.

 

That hand reamer comes in handy to tune up these holes.

 

Here is our loudspeakers in their new home.

 

The loudspeaker wiring on the old speakers was made from microphone cable.

 

We will employ these right angle quarter-inch plugs for the new loudspeaker wiring.

 

The only hard part of using these is getting the solder to tin the case, which is commonly used for the return circuit.

 

We can’t use the cheap stuff now that we’ve gone this far!

 

Sixteen gauge 300v wiring was used for the loudspeaker cables.

 

When assembled, the case forms a clam shell with an integral strain relief.  The extra black wire also serves as a strain relief.

 

Now, all the pieces can be put back together.

 

My favorite part:  First Light from these 6L6 tubes from The Tube Doctor.

 

This thing plays like a new amp.  From 1980.  Because for all practical purposes, it is a new amp from the 80s!

 

Here’s another happy Unbrokenstring Customer!!

 

Thanks for reading all the way to the end!

Contact – David Latchaw EE
Cell – 281-636-8626

Intermittent Sound from a Peavey Renown Combo Amp

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The Unbrokenstring Crew tracks down some intermittent problems in this wonderful Peavey Renown acoustic combo amplifier.  I think we know where to look, so let’s get to work!

The singer/songwriter owner of this amp uses both channels when performing in small venues

The unit is very clean inside and out.  See the Celestions where the Spiders used to be?

The power consumption label started a flame war in the blog-osphere.  Someone said that the power input requirement was the same as the audio power output.  Welcome to the Internet!

We will remove the chassis.  The loudspeakers are now disconnected.

The reverb tank is disconnected here.

Four big long machine screws hold the chassis in the cabinet.

This chassis is entirely shielded top and bottom!  You are looking at the bottom of the chassis.

The white clip holds the speaker wiring in place when assembled.

The chassis internals are exposed.  The audio power amp is rated at 120 watts or thereabouts, and the heatsink and power transistor setup reflects that.

Oops.  Where did this come from?  It was rattling around inside the chassis.

Front panel controls, from left to right.

One channel is called “Lead Gain” and the other one is labelled “Normal Gain.”

The equalization setup can affect both channels using the pedal-enabled ‘Automix’ feature of this amp.

The volume control looks OK from here, so we need to look at the solder joints on the bottom of the PC board.

While we’re working on this, let’s take some pictures to show where all the connectors go.

And we can take a look at everything to see if that loose nut we found earlier caused any electrical shorts.

These fuse holders are very loose.  I’ll change them out when I get the unit apart.

Another pic documenting where the connectors go.

All the knobs need to come off.

Now the controls need to be unbolted from the front panel.  One of my felt-covered sockets is at work here.

My only criticism of this unit is that the knob shafts are nylon, not metal.  But the PC board is free of the chassis.

The fuse holders were weakened over time, and one side came off of each of them.  All will be replaced.

I will use a little different style of fuse holder to get this unit going again.

We’re wielding the soldering iron like a boss today.

Here is a better view of the finished fuse holder job.

I believe that we are looking at the root cause of the failure.  Examine each of the solder joints for cracks.

These are fairly obvious.

I added a little solder flux to the broken joints, then removed the old solder entirely.

I’m moving down the circuit board and reworking all the cracked joints.  Many other joints were bad besides the ones at the PRE volume control.

In every case, the old solder is removed.  The original solder was probably work-hardened.  I don’t want to contaminate new solder joints with the failed material.

Let’s reassemble this thing and see how it works.

I’m particularly nosy around these power connectors.  That loose nut has me thinking that there MUST be some other arc and spark damage somewhere.

Fortunately, the Peavey engineers configured the connector pins on the circuit board and in the wiring harness in such a way that it is very difficult to incorrectly install the wiring harness.

I think that’s all now, folks.

Chassis is buttoned up.  A quick test shows that all demons are exorcised!  But I never found where that nut came from…

Here’s another happy Unbrokenstring Customer!!

Thanks for reading all the way to the end!

Contact – David Latchaw EE
Cell – 281-636-8626

The Prodigal Guitar – Harmony H80S Olympic Strat Comes Home to the Fortunate Son

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Jason Becerra of Cathedral Records is our guest blogger today. He shares an incredible story about how this immaculate Harmony H80 Olympic Strat was won, was lost, and won again. Enjoy the trip!

“I was writing songs long before I could play an instrument. I had notebooks full of lyrics and I had melodies for each song.

“My parents, like many in that era, put me in piano/organ lessons at the mall where they bought a Lowery synth organ for me. I learned how to play ‘When the Saints Go Marching In’ with one hand and I have fond memories of the old woman whose pleasant teaching style was metered only by the not-so-faint aroma of liniment and hard candy. After my year-long course ended, I received my certificate of completion, and that was that.

“A couple years later though, my dad brought it home. “It” was a white on black Olympic Strat copy with a matching head stock. It was the coolest thing in our house and I, of course, was discouraged from messing with it because I had a track record for destroying guitars. When I was about 4, (and I have no recollection of this, I swear) I did my best Pete Townsend impersonation on my dad’s beloved acoustic guitar.

“By the mid-to-late 80s, he’d decided to get himself a new guitar, this time an awesome electric which was purchased, used, at a local pawn shop under the guidance of one of his many musician friends.  I was on a heavy diet of Elvis, Buddy Holly, Jerry Lee, Tommy James, Mamas and Papas, the Turtles, Dylan, Gary Lewis and the Playboys, Gerry and the Pacemakers and of course…the Beatles and the Beach Boys.

“Now, I don’t know if this was by design or by accident, but I experienced the music of the 50s and 60s in the same way my dad did, in terms of age and sequence.  When I was very young I was bathed in doo-wop and rockabilly that laid the foundation for rock and roll.  A bit later, I got to the early 60s: Motown, surf and folk rock, girl groups like the Shangri-Las. Then…the British Invasion hit me with the rabid, frantic pounding beat of the Beatles’ ‘She Loves You’ and Dave Clark Five’s ‘Glad All Over.’  As the music of the era matured and gave way to albums like the Beach Boys Today! and Pet Sounds and the Beatle’s Sgt. Pepper, I too was maturing and growing into myself.

“All the while, my friends (who thought I was more than a bit strange due to my obsession with our parents’ music) were feeding a steady stream of modern music; everything from Bon Jovi and Van Halen to the Cure, REM, Information Society, the Ramones, the Descendents and of course, being in high school at the time, the early 90s music scene hit me just as hard as anything.

“All the while, that black Olympic sat in my dad’s office…just begging me to come take it.

“By 8th grade I had grown frustrated with poetry, essays and stories.  I wanted to say more.  I had more to say, feelings I couldn’t convey without something… without MUSIC.

“One evening, I grabbed his guitar and a “Learn to Play Guitar with Mel Bay Level 1” book.  I studied the chord chart for “G” and struggled to get my fingers just right and after a little while I got all six notes to ring out.  It was magical.  I was sold.  From that point it has been a truly lifelong obsession and it all started with my dad’s Olympic that was generously handed down to me as he realized what he had created in me. Haha!

“I lugged that thing EVERYWHERE.  I knew every corner of it.  I learned how to clean it, how to change strings, how to tune it and I still vividly remember learning the changes to Yellow Submarine and thinking, “Holy Shit!!  I’m getting the hang of this!”

“In 1995, I graduated high school and got a little job while attending university. I saw a shiny new Fender Stratocaster hanging in a guitar shop in Pasadena, TX. I decided to get my first “proper” instrument. I loved it. It had a fancy-schmancy humbucker in the bridge and a Floyd Rose locking tremolo and even though it became my “main” guitar, I still went to the Olympic, all the time. There was something special about it, with its maple neck, the little nick at the 9th fret near the high E string.

“Over the years I had developed a desire to have the Olympic worked on.  The pickups were sounding awful, lots of buzz, the knobs and switch were rusted, machine heads were cheap import stuff and it didn’t hold its tune quite as well as it used to.  It was old when I got my hands on it and I had certainly put it through its paces so it was showing its age.  My friend soldered a random piece of wire onto the back of the guitar inside the cavity where the springs attach…onto the middle hook.  He said it would help with the hum…not so much but he had been playing longer than I, had a jam room in his garage, and owned a van.  Who was I to question?

“By the early 2000s, I was anxious to get someone to work on my Olympic.  I met a guy and I gave him the Olympic with a set of machine heads, a set of Fender hot vintage noiseless pickups, new knobs, and a new switch and asked him to do the work for me.  He said it would take a few weeks and he’d call me.

“Months went by…he stopped working at the store where I met him.  His phone stopped accepting calls.  Nine months go by and I get a random call from him saying he was sorry for being out of pocket but that he was almost finished.  I begged him to let me come get my guitar, no hard feelings; I just didn’t want to lose my guitar.  He assured me he would not fall off the grid and that he’d get in touch with me in a week or two.

“I never heard from him again.  That was 2003.

“For over 10 years, I scoured craigslist, EBay, Guitar Center, pawn shops, everywhere I could think of looking for this Olympic guitar.  No one had ever heard of them.  Truth be told, I had the only one I had ever seen!  No luck.  There is ONE post on a random website where a guy shows a picture of his red Olympic.

“I actually signed up for the discussion board and sent him a private message asking if he’d considering selling it.  No response.  My black Olympic Strat copy had become my unicorn.  Until a couple months ago…

“I was home sick, lying in bed with a nasty stomach bug.  I was looking at Craigslist for my guitar when all of the sudden, I saw one!  I immediately called the guy and said “I’m on my way.”

“I took another look at the guitar and my heart sunk…it wasn’t the same one.  This guy had a blue one…mine was black. Well crap.

“I told him to forget it.  For a couple weeks I was on the fence.  What if I never see another one?  Isn’t blue close enough?!  Am I ever really going to find MY guitar again?  Shouldn’t I just settle for the same model?  I decided to settle. What the hell.  I’d given up.

“I drove over to where the guy had the guitar and picked it up.  He was a nice older man who does garage sales to augment his retirement income.  I asked where he got and he didn’t really remember…his son got it from some guy.

“I took it home and was immediately plugged it in.  Nothing. It didn’t work.  Damn it.  All this and now I can’t even play it! But I stared at it…and I held it and I examined it.

“Curious…there’s a nick right at the high e-string,  9th fret. Hmm…

“The sticker with the “serial number” is scrunched up in the same way I scrunched mine up.  Wait…this guitar isn’t blue! This guitar is BLACK.  Someone put a blue coat of paint on this thing!

“Could it be? Naaaaaaaaaah.  What are the odds right?

“So I called my good friend David Latchaw to give this thing some love.

“While David is working on it, I go back on the trail.  I start posting on Facebook and I get a name of the guy I gave my guitar to in 2003.  I found him on Facebook…..and wouldn’t you know it, he’s “friends” with some friends of mine!  All these years, he’s been right freaking there!

“I reach out to him and he explains what happened all those years ago.  He stopped doing repair work and gave everything he had to an associate of his who was supposed to call customers and return the gear or finish the repairs. Now I had a NEW name.  I started hunting that guy down.  I found a trail of hacked or shut-down websites, bad reviews on forums about “what happened to that guy?  He used to do great work!  Now he’s fallen off the face of the earth!” Apparently this guy fell into some troubles, and that was that.

“But I know he had it and pretty much just sold everything he had to whoever wanted to pay for it.

“Could he be the guy that the old man’s son bought this guitar from?

“David comes back with my new (old?) Olympic and of course it plays like a million bucks.

“As we were talking I asked if he opened the back panel.  He says yeah. I ask what he found.

“He said, “darndest thing, someone had taken a piece of random wire and soldered it to the middle claw… I’ve seen this for grounding, but never on the center claw like that.  That’s a new one.”

“Well folks…long story short…sometimes, what goes around….really does come back around.

“I bought my original guitar 12 years after losing it…and didn’t even realize it until it was back home in my hands and David had worked his magic.  While it was away from me, the machines head actually got installed but the original pickups were left in.  I guess whoever down the line decided to use the pickups I bought on something else.  It also got a paintjob!

“David gets a huge thank you for all his incredible work on this guitar and all the previous work he’s done and the future work he’s going to do.  (I’m going to keep you busy my friend.)

“My wife gets a huge thank you for indulging my music obsession for all these years and never once putting her foot down when I say “I need to get this guitar” even though I always say that’s the last one I’m going to buy.

“My Dad gets the biggest thanks of all…for filling my childhood with music, for never hesitating to lend me his records, for always playing “name that tune” when we were in the car (he quit playing when he said I became better than him) and for the black pawnshop strat-copy Olympic guitar that started me on this little journey as a wannabe songwriter.

“I AM a fortunate son.

“My advice to all of you players out there…it might be tempting, but never let go of your gear. Don’t trade it, don’t sell it and don’t give it to anyone you don’t have 150% confidence in because you could come to regret it for years and years to come.”

Jason Becerra

You have heard the news. Now, here’s the rest of the story.

This head stock just oozes ‘vintage’ and we are not to be disappointed!

We need to replace the controls, including the switch.

Some of the bridge screw holes in the body were stripped, or the screws were missing.  This is an easy fix.

The correct screw for the bridge is an inch long.

We believe that this guitar was painted.  No shortcuts were found in the blue finish.

The original controls were shot.  These are the smaller, 16mm controls often seen on imported guitars.

This is a ‘treble bleed’ capacitor, which keeps the treble from disappearing as the volume control is dialed toward zero.

This is the tone capacitor, that works with the tone control to form an RC network that shapes the frequency response of the guitar.

The tone cap is a polyester film part that checks good.  We’ll use this part again when we reassemble the guitar.

The selector switch is shot.  Jason wants a switching arrangement that selects just the bridge pickup, the bridge and middle pickup, all three pickups, the middle and neck pickup, and finally just the neck pickup.  The factory switch won’t do that, so we’ll use a Super Switch in place of this unit.

The original single coil pickups are in excellent shape.  Each one is labelled with orientation and position.  Then, the pickup wiring is clipped cleanly from the controls.

These pickups will be reinstalled with the new controls.  For now, we will remove them and set them aside.

This is the new Super Switch.  We have a couple of issues.  One, the mounting holes in the Harmony pickguard do not align with the screw holes in the Super Switch.  Also, the lever slot in the pick guard needs to be longer to allow the switch to move fully through all five selector positions.

Here, I get an idea how long the slot in the pick guard needs to be.

This is how long the slot in the pick guard actually is.

Rather than remove a lot of material from a priceless pick guard, we can narrow the selector arm on the switch to not take up quite so much room in the pick guard slot.

Here, I’m reshaping the selector arm on the switch with a mill file.

If you compare this pic to an earlier picture, you can see the material removed from the arm of the switch.

Rather than drill new holes in the pick guard, I’m locating the centers of the existing pick guard holes on the body of the Super Switch.  Again, I do not want to modify the vintage pick guard if I can help it.

The center punched locations of the pick guard holes were drilled for a 4-40 tapped hole.

Here we can see how the new mounting holes are located with respect to the old ones on the outside ends of the switch.

The holes are tapped to match the mounting screws.

I think this is going to work well for us.

The new switch is trial-fitted to the pick guard.  The length of the mounting screws is examined closely to see if they interfere with the action of the Super Switch.

The ends of the slot for the switch were ever-so-slightly widened to allow the switch lever to move fully to each position.  Here, I’m using a guitar nut file for a low E string to shape the slot.

The heads of the new mounting screws were turned down slightly to allow the switch arm to clear.

We have full switch travel from end to end.  This will work well for us!

The potentiometer mounting holes were widened to 3/8ths of an inch to match the bushing diameter on the new controls.

The new controls are full-sized 24mm parts intended for vintage Fender Stratocasters.  This one fits ‘just right.’  I went with 250k pots because the guitar would be very bright-sounding using the original tone cap and 500k pots.

Here are the new controls, set to the proper shaft length for the Fender knobs.

These are all 24mm controls, so I verified that they would fit in the original body routes.  They do!

I stripped off the aluminum shield tape.

I replaced the shield tape with copper.

Using the copper tape, I could now tie the body of the pickups to the same shield as the controls.

The copper solders quickly, without melting the pick guard underneath it.  This ensures that the copper plane is continuous.

Here is the new mechanical layout of the pick guard.

With the new controls mounted in place, the wiring scheme for the five-way switching could be implemented.

The gray cables come from the pickups, and are wired to terminals on the Super Switch.

Wiring for the volume and tone controls is done with solid silver-plated 26AWG copper, covered with aerospace-rated Teflon tubing.  Much of the Space Shuttle Orbiter electronics are wired this way.

This is the finished pick guard assembly.

The output jack wiring, bridge ground wire, and tremolo claw wiring (such as it is) are already attached.  The bridge is set up as a hard tail (no tremolo arm needed.)

The setup and fret polish went pretty well.

Now we have returned, full circle, to where we started. This is an EXCEPTIONAL instrument!

Support Jason’s record label!

Jason’s father Rolando is still making music and making an impact on the music world today. His radio program “Branson Now,” airs on AM700 KSEV in the Houston market. Rolando brings a unique narrative to the rich world of music as only someone of his experience and sensitivity can do.

Click here to see more about Rolando Becerra’s radio program in Houston!

Thanks for reading all the way to the end!

Contact – David Latchaw EE
Cell – 281-636-8626

My Beer Has A Head – B52 AT100 Head

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Chris of Shadow Council told me that his amp head just didn’t sound right after he spilled some “moisture” on top of it. Could the Unbrokenstring Crew take a look and return this amp head to its former metal glory?

Our patient works OK but sounds weak and distorted. Distorted is part of the program, but weak is not.

I think the warranty is out by now, don’t you think?  But I still have these tags on my seat cushions that say “Do not remove under penalty of law.”

A perfect sine wave goes in, and this comes out of the clean channel. We have an issue at or just before the phase inverter circuit.

Let’s look around inside the amp.  At this end of the front panel, we have the power switches and pilot light.

From left to right are the master reverb and master volume controls, and the controls for the CLEAN channel.

The yellow rectangular parts are relays for channel and mode switching.

There are a lot of controls for the OVERDRIVE channel.

I really like the separate circuit board for the input jacks.  This makes servicing the jacks very easy.

Shifting our attention to the rear of the chassis, we see the power amp circuit board at the bottom of the picture.  At the top of the picture is the effects loop send/return jacks and level controls.

At the top of this picture is the rest of of the effects send/return jacks circuit board, with level controls and the foot switch jacks at this end.

The circuit assembly on the left is a ‘Line Out’ jack with its own level control.  The cluster of wires in the middle go to a loudspeaker cabinet impedance selector switch.

Another nice feature is that the output jacks are on their own circuit board, making service easy.  Can you spot the overheated resistor in this picture or in the previous picture?

On the left is the Rectifier Selector switch.  A half-wave tube rectifier circuit, a full wave tube rectifier circuit, or a solid state rectifier circuit can be selected here.  The AC line cord is on the right.

Note that the black plug for the reverb tank goes to the red jack, and the red plug goes in the white jack.  Think about it.

The chassis is out of the case.  Let’s do some tests!

The final amp circuit board has been pivoted up out of the way in order to check circuit wave forms.  Fortunately, the tubes don’t need to be ALL the way in the socket in order to do some tests.  This tube had a bent pin, and I didn’t force it into the socket.  Easy to fix with the power off.

The problem is somewhere around the third socket from the left.  I wonder what’s going on with the contamination?  Beer?  Whiskey?  Probably not vodka.

A pink rag is catching the junk floated off the circuit board with this pressurized circuit board de-fluxer product.

A vacuum tube voltmeter showed that portions of the high impedance circuits around this tube were upset by gunk under the tube socket.

The socket has plenty of gunk of its own and will get cleaned up with solvent and a brush.

Here we see the circuit board underneath the socket.  Some of the residue is conductive and has upset the circuit operating voltages.  But look to the left at the base of the next socket.  See anything?

This socket has been removed as well.  Can you see it?

The Xacto knife points to a trace in the circuit board that has disappeared.

The entire board was scrubbed, sockets were cleaned, and reassembled to the circuit board.  The blue wire bypasses the open-circuit section of the burned printed circuit board we spotted earlier.  This section of the tube amplifies a LOT better when the plate terminal is hooked up to the following stage.

A pair of low value resistors serve as fuses in the high voltage plate circuit.  Component RX is toast.

While we have the amp apart, we can fix the loose knob cover on the “Rectifier Select” switch.

Old glue residue was removed from these parts.  Super Glue is just the ticket for this sort of thing.

If you don’t get it on your fingers, the Krazy Glue works well.  Don’t ask me about the fingers, please.

Now that everything is working, a protective coating will be sprayed over the top of the circuit board to keep ‘moisture’ away from the live circuits.  Each tube socket (and anything else we don’t want coated) is masked off.

This circuit assembly is masked and ready for coating.

Today we will use this commercial/industrial silicone conformal coating.

The spray pattern looks about like this.  I think we’re ready to go.

The circuit board gets four coats.  Each coat is sprayed from a different direction (top, bottom, left, right) to build up a uniform protective coating.  The coating ‘conforms’ to the shape of the circuit board, thus the name “conformal coat.”

I let this cure for a couple of days.  Now bring on whatever “moisture” you want to spill into the top of the cabinet!!

As you can see here, we’re peeling off the masking tape.

Red on white, black on red…  or something like that.

The tube base clamps were cleaned up, ever-so-gently bent back into position, and installed.  These machine screws hold the circuit board to the bottom of the chassis.

All the wiring is reinstalled where it came off.  I take a lot of pictures because my memory may not be perfect.

Just about done with reassembly.

The tubes were in excellent electrical condition. They all go through the tube pin straightener before they are re-installed.

You saw these jacks in an earlier picture.  I took the opportunity to clean and lubricate all the jacks while the amp was apart.

Ah, that’s more like it.  This is a 400Hz sine wave amplified to about 110 watts into a non-inductive high-power resistor.  The bias current to establish Class AB1 operation is just about perfect, judging by the zero-crossing points on this waveform.  Attached to any decent cabinet, this amp would be melting our teeth at this power level.

Support this local band!

Thanks for reading all the way to the end!

Contact – David Latchaw EE
Cell – 281-636-8626