Alamo reverb tank upgrade

[Randall]

I have a Montclair Reverb 2565 in for a cp job. Customer also wants to upgrade from the short reverb tank with a longer Fender sounding tank. The one in it is a Folded Line Type 51, springs are 6", and both transducers are 174 ohm. I believe this to be a solid state circuit and so far I don't find the schematic.

Any suggestions on an Accutronics model replacement?

[Randall]

Anyone willing to take a swing at this?

[Enzo]

Schematic or not, you should be able to tell if the amp is tube or solid state. You should be sable to tell what drives the reverb pan regardless, so if it is a tube amp with a solid state reverb drive, it should be apparent. At that age I have to believe it is ALL tube.

Assuming tubes, either it has a little reverb transformer for drive or it doesn't. If it does, I'd guess a Fender type AB pan. If it drives through a cap off a plate, then a high impedance pan like an EB or FB.

[g1]

I think this schematic the dude posted elsewhere may be it: http://music-electronics-forum.com/a...9&d=1526423358
175 ohm resistance at each end is probably somewhere in the 2K impedance range, so Enzo's FB suggestion should be good.

[Enzo]

Oh wow, I AM surprised. It is a hybrid.

[Randall]

Dang, tough room. Yes, it is a hybrid, that much is obvious. I did say I BELIEVE this to be a solid state circuit, not amp. Maybe my wording could have been better, but give me some credit, please?

So are we in agreement that a 4FB3A1B would work in this "solid state reverb circuit" for a guy who wants a lush reverb?

[g1]

I'd say yes, but I'd check to see which of the jacks on the old tank have grounds insulated from tank shell and re-configure the 4FB3A1B accordingly.

[Randall]

I did that before posting the model #, both are grounded to tank. It's the impedance variable I don't have a grip on when it comes to tanks, and how to figure that.

[g1]

It's the impedance variable I don't have a grip on when it comes to tanks, and how to figure that.

Attached article goes through the code and what each digit/character means. Pg.9 shows the impedances and approx. DC resistance numbers for each impedance.
You said you measured around 175ohm at each end, so it looked to me like closest were around 2K in and out. Enzo looked at the circuit and suggested E or F type for solid state drive, which is most common, and B for output, again most common for solid state.
Very rarely you will see an A input tank in a solid state drive circuit, but it will have a mini SS power amp driving it.

[Randall]

That's a good article, I'm grabbing it. Thanks!