New amp... ...reverb help

***BillSPrestonEsq*** · 07-19-2009, 02:57 PM

I may keep this bad boy, I may sell, but I just picked up a mesa .50 cal with brand new power tubes for $250...

I haven't got the reverb working yet, but I think its just a bum 12at7.

This may be my best deal ever...

So it wasnt a dead 12at7... The reverb knob does absolutely nothing...

Bro Shane · 07-19-2009, 07:16 PM

Wow! Great deal!

And by that I mean I hate you because I never ever find deals like that.

Ax · 07-19-2009, 09:10 PM

probably a bad tank. Mesas aren't known for using lush reverb either. It's like a feature they list on there but don't actually put on there if that makes sense...

***BillSPrestonEsq*** · 07-19-2009, 09:12 PM

Quote:

Originally Posted by Ax

probably a bad tank. Mesas aren't known for using lush reverb either. It's like a feature they list on there but don't actually put on there if that makes sense...

yeah, but I would like it to work.

Major Tom · 07-19-2009, 09:43 PM

Great deal!

Did you look inside the tank? I fixed one where one of the lead wires to the transducer had broken off, I guess from years of vibration. I've also seen 'em with the springs off.

You can also check the transducers for continuity to see if one is open. They vary a lot in impedance, I think most of them will be between maybe 100K and 2000K ohmsDC resistance.

If you don't have a 12 AT7 laying around to try in there, you can put a 12AX7 in just to test and see if you get any 'verb; it won't sound very good, but it would let you know if its the tube.

I would also check the external in / out cables - a lot of amps use the molded end type, and sometimes those go bad 'cause they cable is not soldered at the ends.

***BillSPrestonEsq*** · 07-19-2009, 10:30 PM

Quote:

Originally Posted by Major Tom

Great deal!

Did you look inside the tank? I fixed one where one of the lead wires to the transducer had broken off, I guess from years of vibration. I've also seen 'em with the springs off.

You can also check the transducers for continuity to see if one is open. They vary a lot in impedance, I think most of them will be between maybe 100K and 2000K ohmsDC resistance.

If you don't have a 12 AT7 laying around to try in there, you can put a 12AX7 in just to test and see if you get any 'verb; it won't sound very good, but it would let you know if its the tube.

I would also check the external in / out cables - a lot of amps use the molded end type, and sometimes those go bad 'cause they cable is not soldered at the ends.

no external in/out cables. The tank is internal, (if you can call it a tank)

I thought I saw a broken wire, reflowed the joint, no dice.

I used a brand new 12at7 to check. No dice.

Major Tom · 07-20-2009, 12:05 PM

The springs are in the chassis...? wow.

Did you check the transducers? They must go bad occasionally, since replacements are sold. You may have to take it out of circuit to test it...

You might also check the reverb pot - if it is pc board mounted, make sure no bad solder joint. If has leads to the PC like I think a lot of Mesas have, check the wires. Maybe check the pot for continuity too.

***BillSPrestonEsq*** · 07-20-2009, 01:14 PM

Quote:

Originally Posted by Major Tom

The springs are in the chassis...? wow.

To be honest, If I keep this amp, I may look into a nodded reverb with an added accutronics tank.

Quote:

Did you check the transducers? They must go bad occasionally, since replacements are sold. You may have to take it out of circuit to test it...

I got fed up/ran out of time before I did that. My guess is that that is going to be the culprit,

Quote:

You might also check the reverb pot - if it is pc board mounted, make sure no bad solder joint. If has leads to the PC like I think a lot of Mesas have, check the wires. Maybe check the pot for continuity too.

The pots solder checks out... I need to check for continuity throughout. However, I was offered a brand new assembly for $30 (an official mesa assembly NIB) with springs and transducers. I am tempted to snag that and just skip some testing...