7 posts / 0 new
Last post

Reverb tank for RD100 mystery solved?

I recently received a MM RD100 head with good working reverb. I pulled the tank to get the number. It is an
Accutronics short (9-1/4") 3-spring tank 8FB2A1B
1925 Ohms input
2575 Ohms output
Both input and output jacks are grounded.

This tank is available from https://amprepairparts.com/reverb.htm#8.

There are other compatible tanks that have the input NOT grounded but the output grounded. This would require simply running a wire across from the ground of the input to the ground of the output. Those are:


The MOD tanks are available in those configurations and are sold by Antique Electronics, Amazon, eBay, CE Distribution, etc.

Hope this helps.

bill_moore's picture

I changed the tank in my RD

I changed the tank in my RD One Hundred to the "4" series, and really like it, much fuller reverb!


Long tank in 21" amp

Bill, you did what I've been contemplating a few times. The RD/RP series amps have the smaller tanks in them and they are not nearly as nice sounding as the long tanks found in the larger amps. If you were into surf (or just like heavier reverb) one could try a type 9 tank - that would give you even more.



Which "4" series unit?

I would like to do the same. Which "4" unit did you use?

bill_moore's picture

I'll have to look.

I think it was the 4FB****, but I'll look when I get a chance.

bill_moore's picture

Lars, several years ago, I

Lars, several years ago, I built a "Twin" clone, and did a "shootout" with reverb tanks. I had an old Gibbs from the 60's, a current production,(then), "4" series Accutronics, a "4" series Belton, a "4" series Mod, and a "9" series Accutronics. I had two country players and myself listening while we A/B'd them all. The consensus was the Mod sounded best! I had thought the Gibbs would be the most desirable!
I would have to look, but I seem to recall that the original RD tank had the rounded corners, like the ones made by "beautiful Wisconsin girls", O.C. Electronics. I do think it had an Accutronics number though.


MOD Reverb tanks

I have recently replaced the reverb tank in my 1979 112RD sixty five. It came with the factory OC type 271 which sounded harsh and brittle. This is a short tank with rounded corners. I replaced it with a MOD 4FB3A1B tank. The sound was completely transformed. It now sounds rich, full and natural. It is relatively subtle, not “bathroomy” like some Fender reverb circuits. I would recommend trying this $19 tank in a RD65 or RD100.

Log in or register to post comments