#1
so i am in the process of changing tubes on my B-52.

the company had sent me new tubes and since they are the same kind (not same brand tho), the dude said biasing was not necessary.

i currently took out the power tubes but i do not remember the pin arrangement that they were in! so what am i to do now?

also

i took out the phase inverter tube but it is another brand from the one they provided me with! is this ok? does it really not need biasing?


thanks for all the help!
#2
There is no need to bias preamp tubes. (The little ones) If you are replacing the big ones you may need bias unless of course your amp is fixed bias. Than you just swap tubes. Assuming you have tubes that are in the bias range of the amp.

The big tubes 6l6's, el34's kt77's They will only go in one way. The big plastic pin on the bottom center of the tube is shaped like a key slot to ensure that they will be replaced correctly.

The little tubes 12ax7's are kind of a pain but they will go in you just have to turn them till they slide in. If you noticed they look like they are missing a pin. This is so they will go back in correctly.
If you start a reply with: I have never played one but I have heard good things about it! Your opinion is invalid.
#4
Quote by boxcarmonument
There is no need to bias preamp tubes. (The little ones) If you are replacing the big ones you may need bias unless of course your amp is fixed bias. Than you just swap tubes. Assuming you have tubes that are in the bias range of the amp.
The big tubes 6l6's, el34's kt77's They will only go in one way. The big plastic pin on the bottom center of the tube is shaped like a key slot to ensure that they will be replaced correctly.

The little tubes 12ax7's are kind of a pain but they will go in you just have to turn them till they slide in. If you noticed they look like they are missing a pin. This is so they will go back in correctly.


Wrong. You always need to re-bias power amp tubes in a fixed bias amp to get it sounding it's best. If your amp doesn't have a trim pot to adjust the bias, take it to a tech and get it installed. Cathode bias amps are the ones you don't have to do anything to. The tubes will just only go in if they're positioned right.
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#5
Wrong? In a fixed bias amp they do not have a trim-pot! You have to get tubes that test in the bias range of the amp. As in all the amps manufactured by the logo in your AVATAR.
If you start a reply with: I have never played one but I have heard good things about it! Your opinion is invalid.
Last edited by boxcarmonument at Aug 22, 2009,
#6
alright one LAST thing before i put my amp back together.

the metal pins that hold the power tubes into place are a bit messed up and they are bent a bit more backwards than usual. the power tubes themselves are very securely in place and probably wont fall out.

anyway, is it THAT important that the metal pins be "pinched"?
#7
Quote by boxcarmonument
Wrong? In a fixed bias amp they do not have a trim-pot! You have to get tubes that test in the bias range of the amp. As in all the amps manufactured by the logo in your AVATAR.


Mesa/Boogie are non-adjustable fixed bias amps. They can be made adjustable by installing a trim pot in place of the resistor. The only way you don't have to make this mod is by continuing to use the tubes Mesa rates within their range. Case and point, a Fender Hot Rod Deluxe is a fixed bias amp, but has a trim pot to adjust the bias.

EDIT: Fixed is simply a term for negative grid. http://www.duncanamps.com/technical/lvbias.html
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Last edited by mmolteratx at Aug 22, 2009,
#8
If you have a combo amp I would say yes. Simply because the tension on them will keep the tubes from possibly vibrating out. Being that they are hanging upside down. Or if a head and you don't move it around a lot. You should be fine with it not pinching the tubes.

MMolteratx: Please show where This Link Says fixed bias.


The world standard for a portable, powerful, full-featured tube amp, the 40-watt Hot Rod Deluxe is very aptly named, indeed!

Awe inspiring Fender tone issues forth from a 12” 8-ohm Fender Special Design Eminence speaker fueled by a pair of 6L6 Groove Tube output tubes and three 12AX7 preamp tubes. You get three channels—"normal," "drive: and "more drive"—with gain and master controls for the "drive" channel and a "bright" switch for the "normal" channel. Other features include FX loop, Fender long-spring reverb, external speaker jack, internal variable bias control, two-button three-function channel footswitch, chrome panel with vintage pointer knobs, black textured vinyl covering and silver grille cloth. Cover included
Froms Fenders Website.
If you start a reply with: I have never played one but I have heard good things about it! Your opinion is invalid.
Last edited by boxcarmonument at Aug 22, 2009,
#9
FIRST TUBE CHANGE EVER = SUCCESS

thanks for the help!


1 Success and 1 Fail negate each other right?

for the fail, please refer to other thread "i am so dissapoint in myself"

=P
#10
Quote by boxcarmonument
If you have a combo amp I would say yes. Simply because the tension on them will keep the tubes from possibly vibrating out. Being that they are hanging upside down. Or if a head and you don't move it around a lot. You should be fine with it not pinching the tubes.

MMolteratx: Please show where This Link Says fixed bias.


Froms Fenders Website.


It's an adjustable fixed bias amp. The link I posted in my last post explains it. "Fixed" is simply a term for negative grid bias.
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