Installation of reverb tank

[Leevi]

Can an "open side down tank" be installed "open side up" and
what are the consequences if I do so?
/Leevi

[sluckey]

Yes. In fact, I believe Fender did just that with the Bandmaster Reverb head and Dual Showman Reverb head. They used the same pan that they put in the SR, TR, DR , PR, etc. You may get more boing crash sounds when you bump the amp. And that may get worse as the springs get tired and saggy. I've had my 4AB3C1B pan installed both ways.

[phsyconoodler]

I installed a Fender tank upside down in a JCM 800 I added reverb to and it works just fine.

[Leevi]

I have seen many commercial amps where the tank has been "wrongly" installed.
I think many people don't even recognize that the tanks should be installed according to
manufacturer's recommendations.
/Leevi 

[Tiny_Daddy]

I am thinking the only concerns are horizontal-only tanks versus vertical-only tanks. Other rotations don't matter.

[Leevi]

One rule I have learned is that don't install the tank output close to the PT.
/Leevi

[Tiny_Daddy]

Sometimes the PT can't be avoided. The trick is to orient the tank so that the sensitive pickup (labeled OUTPUT) is away from the power transformer.

[Fresh_Start]

Sometimes the PT can't be avoided. The trick is to orient the tank so that the sensitive pickup (labeled OUTPUT) is away from the power transformer.

It also helps to keep both reverb cables as far away from the transformers, especially PT, as possible.  If you're using a reverb bag, just put the "INPUT" end in first and have the open end pointing away from the PT.

I'm sure Leevi already knows this, but taping a thick piece of cardboard to cover the open side of the reverb tank helps with isolation.  I've been using velcro strips intended for bundling cables to hold the tanks down - avoids the solid connection a screw would make.

Last but not least, I read somewhere that for some reverb tanks the only difference between "open side down" and "open side up" was which holes the springs are mounted in.  IIRC the Accutronics tanks I've used looked like they had two sets of holes.

Hope this helps,

Chip

[sluckey]

Somebody forgot to tell Sunn how to properly mount a reverb pan.   

[Tiny_Daddy]

Sluckey you're right, holding the pan up with rectifier tubes is not a good idea!

[sluckey]

Oh there's a good 1/16th" clearance. The real challenge is tilting that tater masher just right to slip it in the hole without breaking anything. The Sunn boys would probably get a big laugh if they saw that pic.

[Leevi]

I'm sure Leevi already knows this, but taping a thick piece of cardboard to cover the open side of the reverb tank helps with isolation.  I've been using velcro strips intended for bundling cables to hold the tanks down - avoids the solid connection a screw would make.

Yes Chip, the isolation prevents oscillation. I had one case where it helped when I soldered the shielded cables directly
to the pins inside the tank. It is wise to reserve enough space in the cabinet (valid for heads) in order to find a right place
for the tank. The cables play a big role as well. Cheap RCA cables bought from a super market do not work. In many cases it's
better to do your own cables with proper isolation and length.

/Leevi

[Leevi]

I got my head chassis wired and tested it with a open side down tank.
I moved the tank (turned open side up) on the top of the chassis and noticed that it really has a meaning how you
place the tank. Almost in each position the oscillation started with a bigger volume.
The PT was more critical than the OT but also the OT caused oscillation. The only quiet position was
when the tank was crossing the chassis i.e. the both ends were faraway from the transformers.

BUT when I turned the tank as it should be installed (i.e. open side down) the result was remarkable
better. I even found a quiet position for installation. At least in my case I would install the tank
as recommended i.e. open side down.
/Leevi