Fender Frontman Bullet Amp QuickFix



The problems with which this amp suffers are the Bread and Butter for electronic service guys.  Broken power switches and broken input jacks are common in so much gear these days.  Let’s get to work!

02OrigPwrSwThe original power switch was just “plum wore out.”  This was a mechanical problem, not so much an electrical problem.  The contacts were intermittent due to metal fatigue of the components inside the switch and the decay of the plastic used to manufacture the switch.  Out it goes!


The plastic body of the input jack was shredded as well, a victim of time and use.  Funny thing is, Fender continues to use this style of plastic bodied jack on their higher-end amps, which I have considered to be a real weakness, particularly to anyone who uses their gear to earn a living.


My strategy was to replace the plastic input jack with a steel Switchcraft unit that bolted to the front panel, then wire from the terminals on the jack to the proper circuit board pads.  Here I have marked which PCB terminals were tip (T) and ring (R).


The rest of the circuit board was in good shape, with no signs of damage.  The hybrid output amp module (barely visible at the top of the picture) had already been replaced and was still operational.


But I’m sure that you sharp-eyed readers discovered that the Fender chassis was NOT mounted in a Fender enclosure.  Someone in the past had re-purposed an Epiphone enclosure and loudspeaker for service with the Bullet amp.  In the process of melding the two together, they got creative with the mounting hardware.  Yes, that’s a wood screw jammed into the threaded bushing on the Bullet chassis, and bent over to hold it in place.


Just a little higher on the hardware evolutionary scale is this sheet metal nut, jammed over another wood screw.  This was all coming out if my fingerprints were to be found on this thing!


The original line cord would be re-used with the new switch.  Here, I have contrived a strain relief scheme involving a black wire tie and a wire clamp, securely bolted to the chassis.

Anyone who would pull on this would be able to pick up the amp and swing it around, although with a little practice amp like this, swinging it around would not be hard (but could be hard on the furniture.)


This is a closeup of the new power switch.  The body of the switch was round, so the edges of the rectangular power switch hole in the front panel were enlarged slightly with a file so that the new switch fit properly.  As you will see in a moment, the front bezel of the switch was rectangular, which covered the original hole nicely.


Not a bad job on the power switch, I’d say!


Some machine screws were secured that were the proper length and thread size.  Here I’m bolting the chassis securely into the top of the enclosure.


Everything is back together.  On the right end of the panel, you can see the new Switchcraft steel input jack.  It is wired directly to the chassis with short pieces of hookup wire.  This jack will probably outlast the rest of the amp.


This is a front view, showing the difference between the steel input jack (on the left) and the factory Fender plastic jacks on the right, next to the power switch.  By the way, the external speaker jack was also broken, but the owner did not need to use that feature so we left it as-is.


We are ON.  The red LED was smashed back inside the amp, so part of the reassembly process was to secure it back in its hole in the front panel.


The customer was very pleased with the input jack.  The amp works 100%, much to his parents’ chagrin.  Rock n’ Roll!

Gibson Les Paul Studio Shred Rebuild


I am a sucker for projects.  And I’m a sucker for Gibson guitars.  So I saw this black Les Paul at a local guitar store, looked at the price tag, and asked what was wrong with it.  Broken headstock?

This 2012 Gibson Les Paul Studio Shred, sporting a Floyd Rose tremolo system, has a mahogany neck and headstock.  The body is a glued sandwich of maple and mahogany.  Mahogany is a wonderful tone wood with a fine and even grain. However, mahogany is, in my opinion, more fragile than other hard woods. My guess is, this Les Paul was dropped in transit (UPS/Universal Package Smashers strike again!) and the headstock, which is often unsupported in even the high-end graphite guitar cases, snapped when it hit the ground string-side down.

Well, I talked to my bride, who amazingly consented to my newest guitar.  This would be my birthday/anniversary/Christmas gift for the this year.  And the next year.  And the year after that.

The staff at the local guitar store said that they could get me the truss rod tool, original hard shell case, registration paperwork (this was a BRAND NEW guitar!) and get me out the door, incredibly cheaply for a Les Paul.  No doubt the store also received a settlement on the freight-damaged guitar, but I digress…

I couldn’t pass it up and quickly took it to the shop.

Damage assessment proceeded with blocking the Floyd Rose tremolo, stripping off the strings, pulling off the locking nut, removing the tuning machines, and taking a look at where we were.


Amazingly, the veneer over the tuning head, with the Gibson logo, was bent but undamaged!


The break was clean, for the most part, with just a little damage to the finish of the guitar.  However, to get the adhesive repair all the way into the furthest extents of the break would take some thought.


Other areas of the guitar were damaged in the ‘accident,’ and would require some touch-up to the nitro finish.  This could be done on a small scale, with a touch-up pen.  I’d cross that ‘bridge’ when we got there.

My plan was to glue and clamp the broken headstock back onto the neck without separating the two parts and damaging the veneer on the face of the headstock.


As mahogany is a porous wood, I would avoid using epoxy, because the components that make up the mix might penetrate into the wood at uneven rates, potentially compromising the strength of the final bond.  On the other hand, the tension of the strings would tend to pull the joint apart, so I thought that a repair like this would stretch the limits of adhesive chemistry.  Luckily, the locking nut arrangement would keep the tension on the playable portion of the strings, while the remaining string running up to the tuning machine could be entirely slackened after the guitar was tuned and the nut tightened.  Further, I was assured that Tite-Bond glue would create a finished repair that was stronger than the wood surrounding the joint.


I prepared the jaws of my wood clamps with leather.  This is something that I intended to do for a long time, but protecting the fresh nitro-cellulose finish on this guitar motivated me to “git-er-done!”


I poured a little Tite-Bond into a non-porous mixing container.


A little distilled water would thin the wood glue to get it down into the small cracks up against the veneer face of the headstock.


Here, I was doing a literal ‘dry run’ to see how the clamps would work.

TrialClamp2Three clamps may be the way to go here.


Sorry about the blur, but I’m holding the guitar vertically while the thinned Tite-Bond runs down into the recesses of the break.

FirstGlue2Again, things are a little ad hoc while running the thin glue where it needs to go.

BigSquishThe rest of the crack is painted with straight Tite-Bond and squeezed as shown here to blow all the air out of the crack. We’re just doing this once!


The neck, about 24 hours later.  The finish needs to be buffed to remove the marks from the clamps, but the crack is closed with no chipping.


There are three choices for paint touch-up. One is polyurethane automotive touch-up paint, black nail polish, and the right tool for a Gibson nitro finish, e.g. the paint pen.

NeckTouchupBest shot of the Gibson paint pen in action.

NeckPostTouchupThis is the repainted areas before machine buffing.

TremoloCoverCrackMore carnage from the original accident. The tremolo string cover is snapped in half.

TremoloCoverPreTouchupNote the damage to the finish where the impact broke the tremolo spring cover.

TremoloCoverPostTouchupOnce the new cover is installed, this finish damage will be hidden.

NutGroundHere’s a little guitar tech porn. The locking nut is grounded to the rest of the guitar using a flat sheet of copper-plated Kapton tape, rather than a discrete wire;

Nut1More Guitar Tech Porn!

TrussWasherThe washer under the truss rod nut.

TrussNutAnd the all-important truss rod nut.

TrussWrenchHere is a close-up of the factory Gibson truss rod adjustment tool.

NeckBuffoutHere you can see that the finished repair is not perfect but a little finish irregularity is all that is left of our broken headstock.

StringUp1More tech porn. These tuners are not lockers but I’m in the habit of stringing a guitar string through the tuner, then pulling back enough string to get the wrap I want around the post.

TremoloBlockRecognize my Floyd Rose Tremolo block? It’s a nine volt battery covered in a layer of heat shrink tubing.  The covered battery is ‘close enough’ to get the tremolo level on the arched-top Les Paul.

TremoloBlockedThe tremolo block at work.

StringUp2More tech porn. This Floyd Rose was probably built in South Korea.  I may investigate whether the European version is a little ‘tighter’ because the tremolo bar can rattle in the socket, making a clicking noise while working the tremolo.  Probably not what was intended…TremoloCoverTape

Here, a new tremolo cover is fabricated. I used a smoke/translucent cover to show off the springs and tremolo block. Yeah, I’m a geek.  The tape will protect the finish of the new cover.

Tape1Here is my plexiglass ‘mummy’ ready for the edge trimmer.  Once the outline is established, holes will be drilled and countersunk, and the edges will be flame-polished.

StringUp3Even non-guitarists like this pic. Rock and Roll!

Gibson GA-30 Amp Refurb

NewHandleMy father found this amp in a pawn shop in Enid, Oklahoma around 1969.  A high school buddy and I had a guitar duet act, and to support us, he was renting Kustom amplifiers to use as PA systems for our gigs.  I think my father purchased this amp as a way to cut his rental expenses.  The amp worked, and it served me well throughout my high school years.  Unfortunately, I knew nothing of its background and really didn’t appreciate the bit of guitar history it represented until I pulled it out of the closet last year to try it out again.

Before my father purchased this amp, someone had removed the smaller loudspeaker and replaced the larger Jensen loudspeaker with a similar Utah unit, and had changed the output transformer. Perhaps we can update the amp, get it working, and return it to a configuration similar to the way it was Back In The Good Old Days. Well, let’s get to work!

OldHandleThe leather handle was not original. This item was sold as a repair handle for luggage. And now it too was broken.


This bracket used to have a center post that passed through a slot in the original leather handle. The original rivets were weak and were easily removed from the amplifier cabinet.  As a replacement, I ordered a Fender amp handle and hardware (yeah, call me blasphemous, but the flat Fender leather strap is probably closer to what originally shipped on this cabinet than anything you have mounted on your relic Gibson amp.)

FirstLook1I removed the amplifier’s chassis and put it on the bench. We’ll get back to this in a moment.

OldBaffleThe cabinet was disassembled as well.  The old baffle was crudely cut from half-inch-thick particleboard to mount the single Utah loudspeaker. Just after this picture was taken, it crumbled into several pieces and discarded, a victim of age and humidity. A new one would be fabricated from baltic birch plywood to accommodate the second smaller loudspeaker, as an acknowledgement of the original configuration of this amplifier.

New8inchThanks to eBay, I found the eight inch loudspeaker to match the larger twelve-inch loudspeaker already installed in the amp. I just love NOS (New Old Stuff!)  I had agonized over re-using the big Utah loudspeaker or moving back to the Jensen loudspeakers, but the agony was soon ended when I balanced the checkbook. These Utah loudspeakers will be fine for now, as I really wanted this amp as a daily player and not a museum piece.

NewBaffleStartI sketched out the location of the loudspeakers with respect to each other and with respect to the amp enclosure on the piece of baltic birch plywood. Here you can see the starting holes from which the orbital jigsaw will start through the plywood. I do have the router and the circle template, but I opted for the jigsaw to keep the mess to a minimum as bad weather kept this work inside the office.

NewBaffleFirstHoleOne down!

NewBaffleRoutedAndTrimmedBoth loudspeaker holes done and rounded over to minimize edge diffraction. The plywood was also trimmed to fit in the amplifier cabinet.

NewBaffleSealI applied several coats of wood hardener. This stuff soaks into the wood, sealing and strengthening it. The resulting baffle is as rigid and stiff as I can possibly make it. Note – try this wood hardener treatment on old guitar amp cabinets that have become ‘weak’ over time. You might be pleased with the improvement.  The baffle was then painted with a semi-flat black paint on the front side.

TeeNutsThe loudspeakers themselves would be bolted to the baffle using these tee nuts, which were also painted black so that they would not be visible through the grille cloth.

LoudspeakersInstalledHere’s the cabinet so far. Loudspeakers are bolted to the baffle, and the baffle is bolted to the original amplifier cabinet. Only the front (grille) side of the baffle is painted black; you are looking at the sealed but unpainted side.

ChassisNeedsCleaned1The chassis was obviously dirty. Note the clouded tube. This is an indication that the glass envelope of the tube has been compromised and moisture has ‘gotten’ the ‘getter,’ the region at the top of the tube that is usually silver in appearance. We will pull the tubes and check them, but I don’t have really high hopes that we will find many good tubes here.

ChassisCleaned1Here I’ve cleaned the painted chassis with leather cleaner and conditioner, the same stuff that you would use on work boots. It not only cleans well, but does a good job of preserving and restoring the brown paint with which the chassis was painted.  Good stuff!

ChassisCleaned2The top of the chassis is squared away using the leather cleaner. Oh, and all the tubes were trash. But checking the tube layout against the schematics available from Gibson, I discover that this was probably an ‘interim’ model, between the GA-25 and the GA-30. The circuitry is the GA-25 circuit, built with discrete triodes for the phase splitter, and using the four-input circuit of the GA-30 amplifier on a chassis marked GA-30, That information places the date of manufacture of this amplifier chassis around 1949, Fresh NOS tubes are on order from my vendor.

OriginalCaps1Flipping the chassis over, we see the power supply choke on the left side of the chassis. One of the output tube sockets is nearest the observer, and the high voltage caps is the yellow units visible to the right of the picture. The high-pot test on the choke shows that it’s good to over 400 volts.

OriginalCaps2Shifting our gaze to the middle of the chassis, we see some of the black capacitors which are interstage coupling capacitors.

OriginalCaps3Moving to the right, we see the other high voltage filter capacitor and the rest of the interstage coupling caps. These will all be changed out with modern components. As I mentioned earlier, I wanted this amp as a player, not a museum piece. Some collectors will retain the appearance of their chassis by reusing the package of the original component. The wax and internal structure of the capacitor would be removed, a modern component placed inside the package, and the ends resealed with the original wax. Maybe this is important to some people, but this amp has already been worked on, and I want it to play it, not look at it.

NewCapTeflonHere I am covering the component lead of this new interstage coupling capacitor with Teflon tubing. If this style of construction is good enough for America’s Space Program, it’s good enough for me.

NewCapsThe blue electrolytic capacitors are the new high voltage filter caps, and the small white cylinders are the new interstage coupling capacitors. At the top if the picture, you can see a gray wire leading away from the terminal strip towards the center of the chassis. This carries a sample of the output signal back to the preamplifier tubes, implementing a form of negative feedback to the amplifier. This appears to be an aftermarket modification. I left the circuitry in place but left the option to remove the sample tap at the loudspeaker if I don’t like the sound of the negative feedback added to the circuit. This is a guitar amplifier, not a hi-fi.

OPXFMR1The insulation on the output transformer crumbled. This has been worked-on before, and I don’t have the ‘correct’ cotton sleeving used on old electronics like this… nor do I wish to use it here.

OPXFMR2New PVC insulation was slipped over the lead of the output transformer and more wire was soldered to the output transformer lead,  Heat shrink tubing is employed to protect everything. The black thing on the right side of the pic is the nozzle of my hot air rework pencil, perfect for shrinking tubing.

RectifierCheckThis is the first power check. Only the rectifier tube has been installed. The voltages for filaments, high voltage, and bias points all check OK.

PreAndPhaseSplitterCheckThe input circuit is now driving the phase splitter tubes, but the final amplifier tubes are omitted for testing. This allows everything to be checked at ‘no-power’ levels but with realistic loads on the power supplies.

SwitchDisassembledOne issue I found was that the slide switch labelled “Tone Expander” was dirty and intermittent. This switch was disassembled, cleaned, and reassembled. Not a job for the faint of heart.

OriginalLineCordThe power cord was in excellent shape, which meant I probably replaced it back in the 1960s and forgot about it. When I rebuilt the amp, I thought that it was low-risk to leave the two-wire cord in place as there were no ‘death caps’ across the AC line as are found in some Fender amps. However, the chassis was ungrounded except through the metal parts of the electric guitar and thus hum appeared.

New3WireCordSo I installed the meanest, nasty-est, biggest, baddest three-wire cord set that I could find in place of the original line cord.

New3WireCordInstallNow that the shape of the plug established which conductor was hot and which one was neutral, I changed the wiring so that the fuse holder and ON/OFF switch was now in series with the hot (black) wire in the power cord. The green wire safety ground got its own lug at the star grounding point seen in this picture.

InitialTestOne final test before final assembly. A microphone is used to check for hum and low-level signals. Later, a signal generator will replace the microphone and a resistive load will be used in place of the loudspeakers to verify that the output transformer is up to the job of driving four ohms. Output tube operating point will be verified. We are not far from Rock-n-Roll Land now!

WireDressThe loudspeakers and chassis are placed in the guitar amplifier cabinet. The output transformer interferes with the frame of the larger loudspeaker, so it was moved to a place of honor on the baffle. Some sane and rational wire dress keeps things under control, or at least that’s the plan.

TubesInstalledHere are all the tubes. All that remains is to reinstall the back panel and final checkout. This is one of my favorite pictures.

RockinBedroomGo Time!

Teflon Coated Guitar Stand


A few guitar brands, Gibson, for instance, uses nitrocellulose lacquer to finish their guitars. This finish may be easily marred by just touching other objects, particularly when the finish is less than a year old.  In this project, I wanted to explore alternatives to surgical tubing used on inexpensive guitar stands, with an eye towards protecting nitro finishes. NOTE – Special thanks to the local band “Jealous Creatures” who donated this stand to The Unbroken String Crew.

RawTubingThe old surgical tubing that originally protected the guitar from the metal parts of the guitar stand was already gone, so some quarter-inch vinyl tubing would be a good cushion over the bare metal. For most guitar finishes, you could just use this tubing and call it done, but I wanted a layer of something really inert in contact with the guitar.

CutHereHere, the vinyl tubing is cut to length. The plastic end caps would be reused in this project, and the vinyl was cut to length to accommodate them.

TopBracketThis is the support for the neck of the guitar, with the vinyl tubing.

TubingBottomHere, we’re covering the bottom support with the vinyl tubing.

GettingStartedThis is a roll of one-inch-wide Teflon plumbers tape, As you can see, I’ve begun covering the vinyl with the tape. There is no adhesive on the tape, only pure Teflon, so those black end caps will hold the beginning and ending ends of the tape in place when we’re done.

WrappingEach layer of tape overlaps half of the previous layer.

KeepWrappingCrossing over the half-way point, you can see that I just jumped across the bar in the center and continued covering the vinyl tubing with Teflon.



The other end of the Teflon tape is wrapped all the way to the end.

FirstCapThe little black end cap covers the loose end of Teflon.

BottomWrappedThe bottom support is finished.  The top support that goes around the neck of the guitar is covered in a similar manner.

BurnishTeflonNext to the black cap, you can see the overlap in the Teflon tape. To finish the job, I used my fingernail to smooth out the wraps of Teflon. The wraps disappear and the Teflon appears to be painted onto the stand. It’s a little harder to see, but the Teflon wraps near my fingers have been burnished and the wraps disappear.

The finished product.

This project is not intended to be the last word on protecting nitro finishes, but rather is to encourage luthiers and guitar enthusiasts to think outside the box. There is a school of thought that damage to nitro finishes is caused solely by the mechanical pressure on the soft finish, and that this damage can be polished or buffed away. In other cases, some discoloration may occur when the guitar is stored next to leather straps or other sources of chemical impurities, and this damage cannot be repaired without refinishing.

Who would risk damaging the finish on this 1968 Gibson SG Junior in Arctic White? Not this fat boy!























Rogue RD80 – STOLEN – Setup and Product Review



The Rogue product line is the ‘house brand’ of a large nation-wide guitar outlet chain.  These guitars are designed in S. Korea and built in China, intended to be a low-price entry-level guitar.


This particular guitar, a dreadnaught RD80, was a scratch-n-dent guitar, previously owned for a short time by a local school’s music program. It was returned under warranty because one of the tuning machines had shelled out.  To the credit of the local store manager, he honored the warranty AND marked the guitar down further for me.  I happily purchased it, intending to refurbish it for one of my students.


There were a couple of challenges in refurbishing this guitar, as we will see below.  I was not sure that the guitar would be worth the effort, but on the other hand, my student loved the guitar and wanted badly to play it.

OEMtuners The OEM tuners are junk. However, I thought I could take them apart, shuffle in some parts from other tuners, and make them work.  Perhaps a little trombone slide grease and judicious filing and fitting would be in order.


PlasticBridgeHere you can see that the plastic OEM saddle had already begun to experience some serious cheese-slicing from the tension of the strings.  This saddle will be discarded and a synthetic bone compensated bridge will be put on order.  It is a standard size and so will require a minimum of gun-smithing to make the new saddle fit.  While removing the string pegs, I reached inside the guitar to push them out from the inside.  Apparently the holes for the pegs are bored after the bridge is installed, because I could feel chips where the soundboard had broken out during the drilling process.  This is not unexpected from a mass-produced item, but it may be an issue in the future.  Stay Tuned!

TunerSurgery1An examination of the OEM tuners showed that they had ‘some’ adjustment, and could be made functional.


Here you can see the stripped brass gear.  At least brass is recyclable.



After doing some gun-smithing, I re-installed them.  You can see that I left off the covers.  This would allow me to ride herd on the lubrication and keep things in alignment.


What to do about the paint pen?  A little Ax Wax on a rag and some elbow-grease lifted the paint and left the original poly finish in fine shape.  You can see no trace of the paint pen at all.  Thanks for the tip, Pete!


Here we have restrung to tension and checked the neck.  Surprisingly, this inexpensive guitar has a truss rod.

Checkout1Jen checks out the guitar.  After a little playing, the guitar comes out of tune.  Despite the tuners, the rest of the guitar may be nice enough to justify a little more time and effort..


A set of Gotoh tuners were secured via eBay.  These tuners are gold plated, which I thought would look less tacky than the chrome OEM tuners on the black finish of this guitar.  In this pic, I’m reaming out the headstock for the larger 10mm tuners.

DowelSandThe mounting screws on the Gotoh tuners are in a different position than the OEM tuners, so the original screw holes would be filled with this dowel rod, sanded down to about 3/32 inch.  A dab of black nail polish (it’s polyurethane too, remember?) would secure the dowel and finish over the repair, part of which would be underneath the tuners anyway.

DowelClipHere I’ve driven the dowel into the hole and am clipping it off near flush with the headstock of the guitar.

FlushCutThe dowels were trimmed flush with the back of the headstock.  Then, black fingernail polish was used to touch up the repair.  A couple of coats were adequate to seal the wood and leave a nice glossy dot where the repair had been made.

NewTuners1Here are the gold Gotoh tuners installed in the guitar.  The hole filling repair is almost invisible.  And they look nice!  A vendor on eBay has some stock branded “Tacoma” Guitars.  Tacoma was a US-based builder for a while, then were purchased by Fender and apparently phased out.  Look for their hardware on eBay if you want some nice stuff at clearance prices!

NewTuners2Another view of the tuners, with a set of Ernie Ball 80/20 strings that Pete recommended.  Wow, this guitar really sings with the different strings.  Nothing against the Martin set that was on it before, but the Ernie Ball strings really made this guitar come alive!

Checkout2Jen checks out the guitar.  Note smile on face.  But wait, there’s more!

Checkout3OK, here’s the product review.

The Bad :

The soundboard is plywood spruce, and the fretboard is not first-quality wood as there is a funny grain irregularity.  The fretboard workmanship was a little rough and some of the fret wire ends could snag a cleaning rag (or your finger.)  The carnage underneath the bridge, the result of boring the string peg holes after the guitar was assembled, was almost unbearable. A small handful of wood chips were removed from the interior of the guitar.  The cheap tuning machines and cheap saddle was on par for a low-priced instrument.

The Good:

The fret wires were easily refinished and polished and the ends filed smooth.  The funny grain irregularity in the fret board almost disappears if the fretboard is kept oiled.  Replacing the tuners was a no-brainer.  The new strings and saddle made a huge improvement in the sound of this guitar.  After modifications, this guitar has a great voice.

Bottom Line:

My original student changed jobs and couldn’t keep the guitar, so I now use it daily.  I enjoy playing this guitar as much as ANY guitar I’ve owned.  The Martin resonance of the body and the almost-Fender chimey sound prevent me from putting this guitar back on the stand.  I play it until my hands ache.  It is an incredibly fun guitar to play.  I wouldn’t hesitate to perform live with this guitar.  Maybe it’s because I’ve whipped this scratch-n-dent guitar into shape, but I think maybe it’s more;  The exceptional sound just draws me back to this box.  Take off your gear-snob hat and do not cast aside these Chinese guitars.  While you may look at a Chinese for a beach guitar, you may find a diamond in the rough.


UPDATE 23 February 2014 – This guitar, bag, strap and strap locks, electronic tuner, and a couple of sets of strings were lifted out of my office at work.  I never expect to see this guitar again, but stranger things have happened!  So, after all, it’s a good enough guitar for someone to walk past more expensive guitars and take this one.  Rock and Roll!

Bedrock Lead 50C Guitar Amp Checkout


Pete from Pasadena is the proud owner of this like-new Bedrock amp.  Except, it doesn’t play anymore.  As he makes his living doing guitar setups and repairs for a major national chain, he lamented that he didn’t have the desire to reach into high voltage and die.  But he really missed playing thru this amp, which would have been considered a boutique amplifier nowadays.  Bedrock Amps was a once-fine amplifier builder, sued out of existence by greedy capitalists in the day before the Internet, so there are no manuals for this particular model available online.  No Problem, I told him, and lugged the amp back to the shop.



I inverted the amplifier and disconnected the loudspeaker.  To remove the chassis from the cabinet, I had to remove one tube and shield.  Tight fit!



The two large tubes are the EL34 pair.  It appears that the envelope of the tube on the left had been compromised somehow, allowing air and moisture into the tube.  Note that the silver ‘getter’ was ‘gotten’ and turned white.



Sure enough, the envelope was cracked near the base.


This is not an unusual failure mode for vacuum tubes.


The thermal coefficient of expansion of steel, widely used throughout the internal structure of the tube, is about seven times that of glass.  Where the steel and glass meet is right at the tube base.

Worse, with the chassis inverted, the rising heat would raise the temperature of the base of the tube higher than the rest of the envelope, further exacerbating this type of failure.

From time to time, I will see an amplifier chassis with holes drilled around the tube sockets, in an attempt to mitigate this problem.  But we cannot escape the laws of physics forever!



Interestingly, the glass envelopes of these 12AX7s were slightly larger than the JAN-compliant tube pin straighteners in my tube tester.  Not a big deal, because I can unscrew the pin straighteners from the aluminum plate and use the back side of the tube pin straightener to clean up the pins, without interference from the aluminum walls on the straighteners that you see here.  All the tubes in this amp were GrooveTubes, with the familiar clear plastic labels.  But the thickness of the label was not the source of the interference…  the glass envelope is slightly larger than American-made tubes of old.



All of the preamp tubes were in excellent shape, so they were wiped off and set aside for now.



Flipping the chassis over reveals a neat hybrid of point-to-point wiring with an efficient circuit board layout.  All of the components operate WELL within their ratings.  Whoever did the design and construction of this amplifier (reminds me of a Duncan amp…) had the head of an engineer and the heart of an artist.  Here, I’m checking the ESR of all the caps with a Blue ESR Meter from AnaTek.



The only sign of any deterioration I could find was this thin layer of mildew which appeared on the red insulated wire.  And only the red insulation.  You have probably seen this same light-colored dust on Craftsman screw driver handles that have been stored for a long time.  The mildew is of no consequence here, but I cleaned it off anyway.



Time for a new set of final amp tubes.  These are exactly the same type and rating as what was removed.



The white gloves keep finger oil away from the glass.  Yeah, I know that the plastic label on GrooveTubes obviates the need for Clean Room procedures, but I’m old school;  Old habits die hard.



The tube base locks were bent back upwards to grab the tube bases.  As you might guess, this is mildly important on amp chassis such as this one, which live their lives inverted.



Yeah, no matter how many amps I work on, “First Light” always makes the hair on my arms stand up.



These are the 100W eight ohm resistive load blocks that I use to check amplifier performance.  The basic concept of bias checking with an oscilloscope, and performance verification under resistive load is described at various places on the Internet.  Here you see an oscilloscope probe tied right across the load.  Another lead was added to at the same point in the circuit for the THD meter on the bench.



A 400Hz sinewave was applied to the ‘clean’ channel of the amp.  After everything was adjusted, output was gradually increased until the THD meter began to show distortion.  This screenshot shows clean crossover between each output and just a hint of flat-topping (probably the origin of the detected distortion.)  You are looking at 78 watts RMS at 0.1% THD from an amp rated at 50 watts.  As I said, all the components of this amp are conservatively rated and operated well within their parameters, and this is proof.



When I next saw Pete, his grin reached from ear to ear.  His band held a successful audition and he couldn’t have been happier with his band and his amp.  He promises me video…  Stay Tuned!

On Performance

“All the world’s a stage, And all the men and women merely players” wrote William Shakespeare, in his play As You Like It.

Hmmm…  Not much of a stretch to visualize a guitarist up on the the stage.  We’ve seen thousands of pictures and videos (no exaggeration here) of guitarists in performance.  However, even with your guitar in your lap in the most secluded closet recording studio, or practicing alone in the darkened living room, you the musician are exposing yourself in ways that would make the non-musician feel squeamish.  But being up on the stage…  Woah!  Does that terrify you? Are you terrified that someone in your own house would hear you play? Public performance is not why you play guitar, is it?

Let me speak to those of you who haven’t performed in public.  You practice your drills and repertoire diligently, yet you play in private. Why? To what end? “Where is your head at?”

Let us delve into the unseen world of the human mind. Allow me to reduce the workings of the human mind to a more-manageable level by introducing three terms from a field of psychological study called Transactional Analysis:

(1) The Child corresponds to the “id.” The child in you and me offers our most basic, instinctual drive.
(2) The Parent corresponds to the “super-ego.” The parent in our mind tells us what we ‘ought’ to do.
(3) The Adult corresponds to the “ego.” The voice of reality in our mind attempts to reconcile the conflict between the child and the parent.

This is a handy tool to analyze many of the conflicts we endure, and to posit a solution. For instance, the Parent says we don’t practice enough because the Adult says that we must seek perfection. The Child wants to have another cookie and go to sleep.

Or, my parent says that I need to work on this Blog, and my Child says to play another game of Internet Spades. My Adult is particularly weak, so, more often than not, the Child wins out.

Here’s another one. The Parent is fearful of humiliation if we perform our art in front of others, and so the Child is happy to take flight to escape the fear. Thus we run away from the possibility that we perform in public.


What is an Adult to do?

Let me offer a glimpse of something that may be of value to the Adult in resolving the conflict between the Child and the Parent, to the end of moving out into public performance.

Dave Goggin was VP of Data Processing at Gulf Oil Corporation in Houston, Texas up until Chevron purchased the company back in the 1980s. I was fortunate enough to know Dave socially through our joint involvement in square dancing and clogging.

Dave had many roles to play in the day-to-day operations of the Data Processing division. At the time, Dave’s division printed 2.2 million credit card statements a month. He had over two hundred employees to manage. He wore many hats. To keep it all straight, he shared with me the fact that each morning, as he sat on the pot, he read through his personal planning calendar to see what needed to be done at work that day. He said that he would check on a department first thing when he got there, call a field office at nine AM, pick a fight with an employee at 10am so he could fire him, speak at a board room luncheon at 11:30 am regarding changes in billing information in two Western states, go back to his office at 1 pm and close the door for a nap… you get the picture.

He really got my attention about that ‘task’ on his calendar of starting a fight. Other than knowing that he was a Marine radio operator and prisoner of war in the Korean conflict, I never perceived a single mean fiber in his body. Sure enough, Dave told me that work was a lot like acting. He had different roles to play, and he was a ‘real good’ actor. He would fulfill the role of supervisor at 8 am, play the part of a friendly voice on the phone at 9 am, act like a tough guy at 10 am, become a news anchor at 11:30 am, and so on. Driving home at night, he practiced his acting skills while fulfilling the role of courteous Houston driver, which, he intimated, was particularly difficult for him on those days of the week that end in -day.

Dave told me that “All the world’s a stage, And all the men and women merely players.” You act. Even when you don’t want to. Very Adult. …and it seems as if I’ve heard that quote before…

So, the Adult may use the ‘thespian arts’ to reconcile the Child and the Parent. The Adult may now motivate us to behave in such a manner to change us for the better, to cause us to take actions that will improve us, and the world, for the better.

So you have art within you. You are made in your Creator’s Image, so, obviously, a portion of that Image is to be creative.  You make music, dontcha?

You must ‘do’ something to release that art, to give it an existence in the real world. Just as a sculptor sees a statue trapped inside the block of stone, or the wood carver sees the finished carving inside the block of wood, you have a song, a riff, a melody, a chord progression, a lyric that MUST be released. You are powerless to do otherwise. In the current context, you pick up a guitar and create melody, rhythm, lyrics, and/or accompany someone else going the same musical direction as you.

Now you have created the art. What are you going to do with it?  The Adult creates a New Guitarist Person.

My premise in this blog post that you must perform your melody, rhythm, and lyrics for someone else to see. To do otherwise is to hide your art under a basket. Your creation is, by definition, a candle, a point of light, a piece of love. It is something good and of value. This is a dark world, and can use all the light, all the candles, all the love, we can muster.

Further, the act of sharing, of giving, changes you. I don’t mean that your bank account gets larger because you are booked for a hundred dates around the world in the coming year, although it would be cool to find out what that feels like, but rather, your soul is nourished by the act of giving away your art, your creation.

Don’t ask me how this works. The old saying goes like this: in the baseball game of life, you can’t really play ball wearing two catchers mitts. There is a time to catch the ball, and there is a time to throw the ball to someone else, for their benefit and for the good of your team. This, herein is the benefit of performance. Giving has a bigger spiritual effect on the giver than on the audience.                                                                                                                                       2013-03-03_14-13-48_680

To get over the threshold from introversion to giving, the Adult must construct a new theatrical character, and give that theatrical character a purpose, dialog, musical chops, and the opportunity to hone thespian skills. Plainly stated, you are the men and women on the stage. You are the playwright. You are creating not just music, but the character to play that music.  As the creator, you arrange rehearsals, costuming, find a stage, props, lighting, equipment, and promotional opportunities that will allow this new theatrical character.

Haven’t you dressed up for Halloween?  Or participated in the annual “Talk Like A Pirate Day?”

What I’m talking about is creating a new character.  This character plays guitar.  This character has a name (not your real name) and a costume.   You are now “Doing Business As” someone else.  Ever heard of Slash?  The Edge?  Zakk Wilde?  Piggy D?  Their mama didn’t give them their names.

That new person is who goes out in public.  That new person gets the stage fright, not you.

Yeah, that works.  Get out there and let’s see what you’ve got, New Guitarist Person!