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Distorted Reverb - Fix or Replace?

Restored an early 210 Sixty Five (with 12AX7 PI), all working except reverb is harsh and distorted sounding. Anyone know a fix, or should I just replace the tank? I think the one in there now is original, but if not...have we determined what tank is the correct replacement - 4FB3A1B or 8 or 9BB2A1B?


Reverb Tank

I have replaced the reverb tanks on most of my Music Man amps with MOD brand tanks from Amplified parts. If you have the original tank the code should be stamped on it. The difference is night and day.


Replacement makes sense

So is the 4FB3A1B the correct tank for a 210 Sixty-five?


Got the MOD 4FB3A1B, Problem Solved

Received and installed the new MOD 4FB3A1B tank last night, it is indeed the correct tank for the Sixty-Five amp. Looks to be solidly built, and sounds great at all settings. No harshness, no-over-the top sproing, just plenty of warm reverb wash. Highly recommended.


MOD tank

Hi! Great to hear that it worked for you. The MOD tanks sound great in my own amps. I wasn’t sure if the 4FB3A1B was correct for the 210 sixty-five with the 12AX7 and 6CA7 tubes. It is the correct one for the RD/RP 65/100 series but is wrong for the RD50 series.


Reverb Tank for RD50

The RD50 uses a 8BB2A1B tank, the MOD unit is very nice.


More on the RD 50 Reverb

Yes, you are correct the RD50 uses the 8BB2A1B and I still have the original tank in my 110RD fifty. It’s a medium delay, I have experimented with a long delay 8BB3A1B, I could not get that exact MOD tank so I bought a 8BB3C1B and with a little soldering I grounded the input to make it a 8BB3A1B. It sounded really good but I have yet to put it in the combo for long term use. FYI the unmodified 8BB3C1B hums loudly in the RD50 due to the incorrect grounding.


Tried a long delay tank in an

Tried a long delay tank in an RD50, found the delay was...too long. Went back to a medium delay tank.


Medium Delay

I tend to agree. I personally love the sound of the factory medium delay 8BB2A1B reverb.


I'd say roughly half of the

I'd say roughly half of the RD50s I come across have weak or bad reverb tanks. Always keep a few spare tanks around for that reason...


More on the RD/RP100 tanks.

Earlier this year I bought a “barn find” RD100 head (1981, 6L6 tubes) missing the reverb tank. The screw holes in the cabinet matched a short tank so I decided to fit a MOD 8FB3A1B tank. I found that this tank was also not available so I got a 8FB3C1B tank and grounded the input jack again with a little soldering. The short-tank long delay tank worked beautifully with the RD100 head. This is a viable alternative to the longer 4FB3A1B tank if the original had a short tank.


Speaking of Barn Finds

My friends accuse me of running a Home for Wayward Amps and Guitars...and they may not be wrong!

Picked up a nasty, beat-up, dead HD 130 Reverb head a few years back, transformer wires disconnected, no tubes, a real mess.

Turned out someone had removed the insulating board under the main circuit board, so it would short out immediately on power up!

Made a new insulating board, recapped, changed some out of spec components, and retubed. It biased right up and sounded great. Did a full cosmetic cleanup including new repro logo badges from a member of this site.

Came out pretty good I think...



Good job! -mgriffin

bill_moore's picture

I learned a lesson on tank grounding!

A while back I fabricated some cables from a roll of exposed shield wire that I bought to have "correct" wiring in a Fender amp build. The cables were for a SS amp with, (I later found out), 1 side grounded, and the other lifted. I had to insulate the one cable!

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