amp camp revisited

(cross posted from rtopiaradio – op 2016 10 30)

Amp Camp – Recap and Review

To fulfill an ambition to become more self reliant with the maintenance of my rig, I began educating myself on the mechanics of my backline.  Since 1991 that’s been a post CBS Fender Twin with some minor modifications. If you follow this blog, you’ll know I was able to acquire a second, identical model (with slightly more modification).

A couple of months ago I got an email blast from Gerald Weber (Kendrick Amps) about a couple of Amp Camps. The first being “build your own amp” and the second “work on your own amp”. I’ve been playing with a lot of low voltage, solid state gear for the last 10 years. I figured that using “work on your own amp” camp would be the best way to transition to higher voltage gear, complete with a lowered risk of electrocuting myself.

After a couple of arranged payments, I secured a spot for the camp and started pulling chassis in preparation for the trip.

Day -1: (arrived the night before)

Amp Camp is hosted at the Kendrick Amp facility near Killeen/Ft Hood (TX, natch).
My enthusiasm for the event was multiplied by anticipation of getting my first Whataburger since leaving El Paso in the summer of 88. 

Day 1:

I was so busy with filling my own orders (Monorocket) that I missed receiving the itinerary email, so I had no idea what the schedule was. I decided that 0800 would be a good guess so I started my day the TX way and headed to Kempner (one town over):

 0800 turned out to be two hours early and I was the only attendee at the ranch. Fortunately, one of the Kendrick staff was already there and had everything open. This gave me time to set up, settle in, drink shop coffee and hang out with Geralds dogs (both named Max).

One of the first “other attendees” to show up was someone who attended the previous weeks amp camp. In addition to building the kit, he wanted to work on his gear just like I did. He showed up early to get a jump start on repairs using everything he’d learned so far

Once all the other attendees arrived, things took a more positive turn. Everybody was really cool and friendly. Gatherings like this tend to go either way: either everyone’s really cool and ready to revel in shared interests or each person stakes their own territory and works in isolation. 7 attendees x 2-3 amps each = a good stack of cool gear. There were Bandmasters, Super Reverbs, Bassman heads and even some Ampegs (a Gemini and Flip top bass amp) and a handwired, scratch built JTM45 clone (which was way more immaculate than anything I’ve ever seen Marshall do).

By the time everyone started calling each other by first names, a door opened behind me and in walks Gerald Weber. Without missing a beat after introductions, he launched into a ice breaker joke and started the instruction (I’m not sharing the content – that’s what the tuition pays for)

The only thing I will share is that all of us were guaranteed that everything we were about to do was really easy.

The format was mostly informal and hands on. After dropping some rudiments, we were all sent to our stations to fire up soldering irons and start fixing.

I’ll confess that I did a lot of prep before coming down (helps reduce information overload). I’d even watched a handful of youtube vids that Gerald did. Replacing filter caps and coupling caps before anything else is apparently SOP.

I’ve had my primary amp “overhauled” twice since 1991 and was really disappointed to find out that neither serviceperson replaced any of the filter caps (or most of the coupling caps).



After doing the cap job in both of my amps, the rest of the first day was spent on my primary amp (Norco). The only thing I didn’t do was fire it up for a functional test.

Day 2

I showed up early again knowing that I could get a head start on amp 2 (Flames).

Better than the hands on training. were the decades of product knowledge between Gerald and Johnny. This was worth the fee alone. These guys have probably seen and forgot more stuff than I’ll ever know. As mentioned earlier the other attendees brought a a wide spectrum of old gear and they had anecdotes and history for each piece.

all recaps complete:

(cap graveyard)

The best part overall was firing up my amps first the first time after doing all the rework.
Prior to coming down the Norco Twin was operating intermittent and the Flames Twin was humming.Both amps were running clean and quiet.

Before I left I’d consulted with Johnny about some mods to the tone stack. I was ready to drill a hole in the back panel for a switch, but he was more than happy to walk me through the mod using the existing BRIGHT switch. Naturally, anyone with this much backstory on the amps knows that the BRIGHT switch is usually on anyway, so why not make that setting permanent and use the switch for something else. I executed that mod before loading the chassis back in their cabinets (after I got home).

Bottom line: I want to do this again. The chalkboard time was primer enough for me to make the jump from PCBs to handwired/IC to tubes. Now I’m prowling the flea markets and yard sales looking for vintage pieces that need repair, to give me an excuse for going through this again.

my twins

(reposted from rtopiaradio with edits and amplifications)

(post in progress)

chapter 1 – the origin story

1991 Norco CA – I bought a 1977 Fender Twin (ser A768591) from some guy named Viv, who lived in a geodesic dome.

Date and time unknown – my friend Jim “Flames” Brennan bought a 1977 Fender Twin (ser A769024) from somebody in the wilds of San Bernardino County CA.

Both amps were initially serviced by Smokey “The Amplifier Man” Stover.  Both amps had the Pre CBS mods done. They were also completely recapped (including some caps replaced with polystyrene). Flames also opted for Smokey’s “Grunch” mod (which removed the master volume and tremolo and replaced the “intensity/speed” controls with “grind/crunch” controls) .

I’ve forgotten exactly how the “grunch” mod works on a technical level. I just remember that I wanted to keep that part of my Twin stock.

Flames used his Twin (the Flames Twin) until approx 1995 before selling it to a friend.

After nearly 30 years, a couple circuit mods and a few speaker and power tube configurations (KT88’s and currently 6550’s) it’s been my primary amp.

In 2013 I was able to buy the Flames Twin from the person he sold it to. The cabinet was already in bad shape when Flames originally bought it. The repairs that held it together for nearly 20 years didn’t survive the cross country journey (it appears most of the damage happened on on a crater infested section of I40 between Garth Brooks Blvd and OKC – that section of interstate has been improved).

chapter 2 – the reconstruction

The cabs were made from scratch by the same vendor that built my eurorack cases. Theyre solid pine with some joint enhancements (better than CBS did) to make them stronger.

step 1 raw
roundovers 1 (note: circuit housing stored on shelves)
roundovers and final sanding
rear view (note: half closed vs open)
waiting for cabs to be finished