Which Reverb Tanks for Which Models?

msaudio

Ok, I'm a little confused here. CE Dist (AKA Antique Electronics) lists two different long Accutronics-type tanks for MM amps: 4BB2A1B and 4FB3D1B. The BB has a 150Ω input impedance and the FB is 1475Ω. Big difference!

Presumably there's a change as of a given model series. The amp in question is a 212-75 (2475-75). Reverb and phaser (although phaser is marked "tremolo"). 2x6L6, cathode-driven. Looks like the CD-3 driver board. Dead tank has an open output coil, and is marked 4FB, but I'm not sure if it's the original tank.

I might just try the EB and split the difference. :-)

Ideas, anyone?

Full Name
Mike Griffin
Music Man Equipment
MM 112-RD-65

Member for

11 years

mgriffin155 Wed, 06/15/2016 - 17:56

Check out this page: http://amprepairparts.com/reverb_numbering.htm
It shows FB for MM amps. The lower impedance EB models might work but may overload the driver IC a bit effecting "sound quality". Don't waste your time with the 150 ohm BB models in your 2475-75. My 112-65RD has the same driver circuit and it uses the shorter 8FB tank. Good Luck. -mgriffin

Full Name
Bill Moore

Member for

11 years
Profile picture for user bill_moore

bill_moore Thu, 06/16/2016 - 07:55

I replaced the short tank in my 115RD with a 4 series, I like the reverb a lot better!

Full Name
Mike Schway
Music Man Equipment
I'd like to think that I service all of them.

Member for

8 years 9 months

msaudio Mon, 06/20/2016 - 14:01

Thanks, all. Input and output grounds both isolated, right? (fortunately that's utterly easy to change with the newer Asian tanks...just a solder bridge on the jack PCBs)

Which models used the BB (150R) tanks?