power tubes cathode bias bypass cap REMOVED FAST.

[Colas LeGrippa]

Buenos dias, my friends.
I have modified a Bogen L330 which took me way more time that I had expected:( and gave me much less money too !! )


This amplifier had been modded before and here's what I found and did : bad filter and signal caps, non shielded signal wire, one bad 5Y3 ( this model is a dual rectifier ), 2 bad tube sockets, 2 cold joints, voltage rectifier defective ( removed it completeley ), swapped the 2 X 6AV5-GA for 6L6, with gr2 protection, cathode bias ...you know the game.


Here's what has been the problem: After replacing the power tubes and biasing with a 390 R / 10W  ( 50mA @ 400 V ), the amp was sounding very good. ( I must say that I have added a master volume , removed the tone stack and put a simple tone control --the Ampeg Reverbrocket design, very efficient--. Then I said to myself: --Colas, you forgot to put in a cathode bypass cap !. Ok , I look in the messy drawer ( I have only one drawer ) and find a 33uF @100V , axial , the perfect part to put in. I plug the beast, a speaker, turn it on. Suddenly, without no guitar  plugged yet, a loud voice starts to shout out of the speaker saying : '' WE CAN'T HANDLE THAT EXTRA GAIN, REMOVE THAT CAP''.  I listened to the voice just like I listen to my wife and removed the bypass cap. Everything went back to ''normal''. Called up my client: Alain, your amp is ready''. Picked it up after giving me 3 bills, called me two hours later.


''Jack what did you do to my amp? This is the best sounding amp I never had !!!''


''Huhhhh, I tried to fix it properly, Alain......''


.........I was able to modify an awesome amp, but I can't say what happened with the bypass cap...
Jack of all trade, master of none.


Colas LeGrippa

[tubenit]

Cool story!  I appreciate you sharing it.  It's a good illustration that sometimes we need to think outside the box and explore reasonable approaches that we might not have tried otherwise. 

No matter how much time I have spend or am spending on amps, I continue to learn something new.

With respect, Tubenit

[super&plexi]

I've never completely liked my 5e3..started with 47uf, 33, 25, something like that. Hated it. Dropped to 2 33 series, then 22, then finishing up 8 or 10, for whole P.S.                   like better, but still meh/lukewarm.      All through these changes never got around to changing


Kbypass: 100x100


Gonna Change to 25 x25 (found Sprague atoms at garage sale)  or some lower, or none.


If sounds/feels much better will post.