Mesa Rectoverb 50 Reverb tank

[mtlbasslad]

Greetings all,

To be specific this is about a Mesa Single Rectifier Rectoverb 50 (second version, no tube rev driver0 I don't really know the name of the device that replaces the tube...)
So the tank is dead, & the 9BB2A1B seems to be unobtainium. This tank is 150 ohm input & 2575 ohm output, how critical the these numbers? I can get a 4BB2A1B which is 150 input/ 2250 output.
Is this an acceptable substitute?

While we are at it, the amp came to me with the tank out & cables from reverb to chassis out. The tank is labeled in/out but the chassis is not. Any danger flipping them around until we find joy? Or a way to test the chassis connections?

Thanks in advance,

Lorne

[g1]

The tank numbers are close enough, but the 4 is the full size type, do you have room for it?
You can check the cables at the amp end by touching the tip. The one that gives you hum when you touch it is the return and goes to tank output.

[mtlbasslad]

The tank numbers are close enough, but the 4 is the full size type, do you have room for it?
You can check the cables at the amp end by touching the tip. The one that gives you hum when you touch it is the return and goes to tank output.

Hey g1,
The 4 & the 9 are the same size - the 8 are the short ones. The 4 has 4 springs the 9 has 6. Totally logical !!
I'll be testing that tip/hum soon...

I wish my 'customers' would take pics or label things when they take things apart... sigh

What do you think the 'close enough' values will do to the reverb function ?

[The Dude]

What's wrong with the tank- broken springs, open transducers, etc.? Have you checked the wires from the RCA jacks to the transducers? It's not uncommon for one to break.

[mtlbasslad]

What's wrong with the tank- broken springs, open transducers, etc.? Have you checked the wires from the RCA jacks to the transducers? It's not uncommon for one to break.

Open transducer - one. Yes I checked those skinny little wires, not the case. Too bad for anyone who wants the original tank - not made anymore. even Mesa/Gibson have none. I'm not really up to rewinding a transducer, after taking apart what seems to be spot welded things... I have my limits LOL

[Jazz P Bass]

Out of the amp, the input cable rca plug is not grounded. (I believe it is a single wire)
The output rca plug ground is at ground.

[mtlbasslad]

Out of the amp, the input cable rca plug is not grounded. (I believe it is a single wire)
The output rca plug ground is at ground.

It amazes me how well you people can read a schematic... so it's a 5532 opamp that's doing the work? And what is J175 doing? Will I live long enough to understand all this? LOL

[The Dude]

Yes the 5532 supplies the reverb gain. The J175's gate is connected to the footswitch through the 22k. The FET shorts the reverb signal to ground (or doesn't) to turn the reverb on and off.

[mtlbasslad]

Yes the 5532 supplies the reverb gain. The J175's gate is connected to the footswitch through the 22k. The FET shorts the reverb signal to ground (or doesn't) to turn the reverb on and off.

Thanks Dude, I think can can actually understand that. Let's hope the 5532 is healthy, 'cuz I bet it's not socketed...

[mtlbasslad]

New tank arrived & is working fine - thanks all for your help !

[Jazz P Bass]

Nice!

[mtlbasslad]

Oh-Oh I spoke to soon - sounded good with a signal gen but not with a guitar. Back to square one. Replace the 5532 ?

[g1]

Either that or try disconnecting Source or Drain of J175 first.

[mtlbasslad]

Either that or try disconnecting Source or Drain of J175 first.

I like that idea, since of course the 5532 is not socketed. Please expand on 'Source or Drain' just clip one leg of J175? Any leg? If J175 is out of the picture then no pedal on/off for the reverb, it will be always on & just dial it back if not needed?

[g1]

Yes, with the J175 disabled, the reverb will be 'always on' and controlled by it's pot.
Pin 1 is drain and pin 3 is source, so either of those outer pins can be snipped. What I do in that situation is clip the whole fet out, snipping as close to the board as possible. Then, if it is not the problem, when you go to replace the op-amp you can re-install the fet.