Rootbeer Audio

hi all,
a winter update >>> I closed up shop in October so that we could prepare for the arrival of a baby >>> well/well/well/well >>> about two months ago we welcomed a small human by the name of Oliver into our house & lives >>> happy to report that everyone (humans & critters alike) is/are healthy, happy, and staying warm ~ >>> with that being said…
R O O T B E E R A U D I O reopens this week for repairs, restorations, custom amps, kit builds, foot switches, cables, and so on and so on and so on >>> for more service & ordering info/procedures, take a look at the SERVICES section of the site (link in bio).
education >>> want to learn how to make a pedal or simple oscillator (bleep blip boop)? or about ohm’s Law, signal-flow, & why that microphone shocked you on stage? I’m currently accepting online & in-person lessons >>> more info in the EDU section on the site (LiNK in gOT dang BIO )))
in closing >>> due to some life changes, Rootbeer Audio is more of a full-time gig than it has been in the past >>> I had to restrict the work and projects I took on as I became busier throughout the past few years, but it’s a new dawn >>> have an idea? want me to fix all of your amps at your recording studio in the Catskills? want to host a pedal workshop at your office? want to build a 10,000 watt KT88 public address system? let’s talk.
>>> thanks for reading, Matt

This Marshall handwired 18watt reissue (1974x) amp came in with a weird//troubling noise.
At first it sounded like a bad tube noise, but then started to sound/feel like a bad connection. Upon opening it up (and after some quick tests like swapping preamp tubes, etc) I noticed the first issue... one of the screws that holds the back plate on was either touching a resistor on the volume pot OR it had pushed it at some point and had made the solder joint intermittent. I resoldered it, patted myself on the back for finding it and moved on (see last photo).
But the sound was still there. I ended up spotting some cold solder joints (especially on the tube sockets), so I ended up resoldering the majority of the preamp. I thought I fixed it --- but the issue persisted. The issue seemed to be caused by mostly physical poking and prodding (which was sorta different than what the initial tests suggested). After using the scope I was able to determine the issue was right before the phase inverter. I tested every resistor, cap, and resoldered everything. Around this time I noticed the underboard connections were pretty suspect, so I ended up removing a few and resoldering them to the top of the turrets.
After all of this work, the issue sorta persisted. I say, "sorta", because it became apparent I was chasing two sounds --> one which was an intermittent connection, and another which was a bad power tube.
After a ton of investigating, resoldering, and tube swapping, I ended up replacing the two gold lion powertubes with trusty el84s and the amp was fine ever since. I also serviced it (cleaned/tightened everything) and installed a bracket to hold the attenuator in place.
The amp did have two compounding issues -- and while I initially thought power tubes could be at play (but at one time the volume control seemed to help the issue which would negate that), I never would have considered there could be two problems at once.
I'm reading zen & the art of motorcycle maintenance so I'm one step away from getting too big-picture//deep with this one and my assumptions, but most importantly, the amp lives again! Enjoy the amp Nick!

A Fender Pro Jr. —-> this smaller counterpart to the blues jr came into the shop with its original tubes and some complaints of noise. Upon testing I noticed V1, the first preamp tube, was microphonic as hell, and the original power tubes were nearing the noisey//inconsistent stage of their life. Like many of the modern-ish fender combos, the line in the sand for any repair is whether you “drop”/dismount the PCB (which has the pots, jacks, etc soldered directly to it) or leave “well enough alone”. Often the issue is a broken input jack or something that makes the decision for you. But in this specific case, since it has its original nearly-20-year-old filter caps, a wonky input jack (but functioning), and the owner plans to keep it for the long haul, we decided to go all-in.
After the usual cleaning//tightening of everything (especially the baffle —- if you have an amp that remotely resembles this, check those screws in the corners that hold the baffle in!!), the amp received new F&T filter caps, new JJ el84s, a new preamp tube (V1), a new metal switchcraft input jack, and bias. This small (but deceptively loud with two power tubes) amp is ri ri ri ri rippin!¡!¡!Enjoy the amp George and Julian!

This ~1968 drip edge Twin Reverb came in for a spruce-up before some recording sessions. The amp was last serviced around 10 years ago (or according to one date scribbled inside, maybe the aughts) at which point all of the electrolytics were replaced. Aside from a sketchy, ground-plug-missing power cable and a baffle that was falling out, the amp worked well! But like many of these jobs, once they're under the knife and you get to testing, you find some worthwhile small repairs.
The amp received the usual servicing//tightening//cleaning, a new fuseholder (the original was stripped), a new standby switch, a new pilot light bulb (I rarely need to replace these), a new power cable (and removed the death cap), new power tubes and bias, and a thorough reflowing/tightening of all the chassis grounds. After that I fired it up and it was working mostly great! However after some testing and scratchy pots I realized the majority of the blue coupling caps were leaking a relatively large amount of DC. After that, I added a cap to tame the "tick" of the tremolo, added an RCA "dummy jack" so it works without a foot switch, and got to work on the cab. I drilled some new fresh holes to hold the baffle, added two small L-brackets, and tightened it all up. 10 or so hours of burning-in new tubes and a loud stress-test and it's good to go for recording! Enjoy the amp Brian!