silentrage
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- Mar 3, 2009
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Hey guys, I've scoured the net and couldn't find this information, but I'm also exceedingly bad at finding things so help me out. 
I asked buzzy, the tech who helped me out with my mark 3 about installing a bias pot. He said a couple of things, one is that bias pots he sees a lot are 10k, but I know some fellow members here use 50k, is there a big difference?
He also said it's a good idea to change the resistors and caps in the bias circuitry so that they can accomodate the bias range you're attemping to achieve, any idea how one goes about figuring out the values needed for a hotter bias? The posts I remember seeing about people who did their own bias seem to involve only a pot added to R117, is the amp built well enough that you can adjust bias this way and still have the amp operate within tolerance?
And lastly, I measured the plate voltage (pin3)on my mark 3 to be around 474v, and the bias voltage (pin 5) to be -47v for the outter pair and -58 for the inner pair.
The current reading for pin 5 is 14ma for the outter pair and 18ma for the innter pair.
So the big question: How do I calculate where 70% dissipation is? and what do do I need to do to get it close to there?
Edit: I'm an idiot, I figured out the first part, 25w for 6L6 divided by 474 = 0.053a.
0.053 x 0.7 = 37ma, that's what I want for 70% dissipation I guess.
I asked buzzy, the tech who helped me out with my mark 3 about installing a bias pot. He said a couple of things, one is that bias pots he sees a lot are 10k, but I know some fellow members here use 50k, is there a big difference?
He also said it's a good idea to change the resistors and caps in the bias circuitry so that they can accomodate the bias range you're attemping to achieve, any idea how one goes about figuring out the values needed for a hotter bias? The posts I remember seeing about people who did their own bias seem to involve only a pot added to R117, is the amp built well enough that you can adjust bias this way and still have the amp operate within tolerance?
And lastly, I measured the plate voltage (pin3)on my mark 3 to be around 474v, and the bias voltage (pin 5) to be -47v for the outter pair and -58 for the inner pair.
The current reading for pin 5 is 14ma for the outter pair and 18ma for the innter pair.
So the big question: How do I calculate where 70% dissipation is? and what do do I need to do to get it close to there?
Edit: I'm an idiot, I figured out the first part, 25w for 6L6 divided by 474 = 0.053a.
0.053 x 0.7 = 37ma, that's what I want for 70% dissipation I guess.
