Reverb replacement for the Fat Boy

You can take the "boi" out of "boing..."
Not working to spec

A few months ago, I noticed that the Accutronics 1BB2A1B reverb on my mighty Carlsbro Fat Boy suddenly started to sound terrible.  I just replaced it yesterday.

Yeah, you read that correctly.  I noticed this a few months ago, and only did something about it in the last 24 hours. If this gear belonged to anyone else I know, I would have been all over them to fix it. In fact, I probably would have dragged it home and fixed it. But this is MY gear, so I’ve been playing trucker music for months with no reverb.   Yay me!

While this is a simple repair, there is very little information out there about how to actually get the parts you need and do it.  I’m filling this post with search engine bait, so if you found it, that worked.

 

The big fail

The failure itself was pretty simple:  One of the wires that holds the spring mounts broke off, and it did so inside a mounting piece that is soldered in place.  A better person that I could probably fix this, but it is extremely fine and fiddly work, and I am pretty constantly reminded that I am not a better person than I.

 

The bigger problem

The main problem is that the stock reverb tank in the Carlsbro Fat Boy is a 1BB2A1B. That becomes a pain in the butt for the handy lazy person, because searching for 1BB2A1B and your amp name or “replacement” gives you pretty much no useful results on the major search engines.  Neither does “reverb spring repair” by the way. Lots of links for people who will replace your ‘verb for money, but you probably don’t need that.

Hopefully, your search now leads you here.

 

Reverb codes, briefly

Spring reverbs are a rare kind of product, in that there is a standard numbering system for identifying pretty much everything about them, and everyone in the industry uses it.

Apparently, that kind of standardisation is easy to do with physical objects made in different parts of the world over decades, but pretty much IMPOSSIBLE to do in software.  But I digress…

You can find a key for the reverb numbering system all over the place. Here’s one with information about Accutronics reverbs at the top, and the numbering system at the bottom. Seeing as most of the reverbs that come stock in amps are Accutronics, that’s a good place to start.

The chart tells you this about my 1BB2A1B tank:
1 – It’s Type 1, which means it has two springs and is short (9″)
B – Input impedance is 150 ohms*
B –  Output impedance is 2250 ohms*
2 – Medium decay time (1.75 to 3.0 secs)
A – Input and output are both grounded*
1 – No lock
B – Mounts horizontally, with the open side down

I liked how it sounded, but truth to tell, it’s a pretty cheap-ass tank.  Short, two-spring verbs can be kinda theeen.  Doesn’t matter though, because pretty much no-one makes this exact tank any more.  You’ll be hard-pressed to find any Type 1 tanks from anyone.

 

Getting tanked

My tank was an Accutronics, so I went to the Accutronics site.  I couldn’t find any info there about a 1BB2A1B, and I knew that some of the specs of my old tank needed to be matched on whatever new one I bought.  I was most concerned about the input and output impedance and grounding, which is why I marked them with an “*.”

I ended up calling one of their distributors, CE Distribution.  CE is a distribution company, but they run a few places that sell to end-users. They have the same support for all of them, including Antique Electronic Supply.  I talked to Sam on the phone, and he’s awesome.

 

A steady guide in some celestial voice

I’m not going to get into the What Kinda Reverb You Want and Why discussion here. This post is already way too long to start talking subjectives.

The important things when choosing a replacement:

  • The input and output impedance must either match your old tank exactly, or you must nerd out and learn what happens when they don’t
    (hint: avoid having to do that)
  • Same goes for the grounding
  • Check the size of the tank versus the space you need to install it in. Remember that you have to plug the thing in, so if you don’t have AT LEAST 1.5″ clear in front of the plugs when the tank is installed, you’ll have to plug it in BEFORE you mount it
    (hint: avoid having to do that)
  • For something that can be a big part of your sound, reverb tanks are pretty cheap

I couldn’t find anything by Accutronics that would drop right in, so I got a MOD 4BB2A1B to replace my 1BB2A1B.  Pretty much the same tank as the 1BB2A1B, but 17″ long, which is accomplished by doubling the springs lengthwise.  All the electronic specs line up, which is the important part if you want to be simple about things.

 

Installing a horizontal spring reverb tank

There never seem to be instructions for this anywhere, and most searches for it just point to to reverb tank reviews that say useful things like “installation was easy!”  or “installation is easy!”  Search is horrible now.

On the Fat Boy, and most amps with the ‘verb installed flat across the bottom of the amp with the open side down, installation is really easy! LAWL.  It’s nice to have instructions though. You should read all the way through them first.

Removal

  1. Open up your amp
    (hint: I dunno, look it up if you need to!)
  2. Look at the input and output jacks to the reverb. Note what colour each is.  Write it down.  I SAID WRITE IT DOWN!
  3. Undo the input jack
  4. Seriously!  There is NO colour-code standard for input and output.  LAST CHANCE TO WRITE IT DOWN
  5. Undo the output jack
  6. Remove the screws holding the tank in place, and keep them
  7. Remove the tank

NOTE! If you are inside a combo amp, your reverb tank is under a big ol’ magnet.  That magnet is going to grab the tank.  This is annoying.  You can’t stop it.

Installation

NOTE! Remember when I mentioned the big ol’ magnet?  Dude!  It was like, three lines ago!   That magnet’s going to want to grab the new tank too.  If the tank is painted, the magnet will scratch the paint.  It WILL.  I highly recommend that you hook up the new tank outside the amp FIRST, make sure it works, and then install it.  No-one wants to take back a scratched tank.

  1. Connect the inputs and outputs.
    SEE?  TOLD YA TO WRITE IT DOWN!  The magnet-wrasslin’ makes you forget
  2. Test that the reverb works
  3. (netdud only) Take out the piece of foam they put under the springs for shipping, stop swearing, and test again
  4. Turn off the amp, disconnect the reverb
  5. Make sure you have squishy grommets in the screwholes you are going to use, so the tank is physically isolated from the cabinet
  6. Wrestle new tank into place, scratching it on the magnet at least once
  7. Make sure you have room to plug in your input/output jacks
  8. Screw the tank in place (Heh.  I said “in place…”)
  9. Hook up the tank
  10. Test
  11. Close up your amp and play!

 

 

Leave a Reply

Your email address will not be published. Required fields are marked *