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previous: Matthew D Wow, Thanks a million Enzo!... -- 5/22/2003 1:25 PM

Re: bias adjustment mod for B15?

5/23/2003 5:19 AM
Enzo	Re: bias adjustment mod for B15? Cool, your schemo saves me the trouble of getting out mine. Either place ought to work. If you work on the 100K/56K pair, make the bottom one variable. You do not want the possibility of turning the bias off completely, so rather than replacing the 56K with a pot, I would replace it with a pot and resistor. That way if you turn the pot to zero, the resistor will still establish at least a minimum bias voltage. I would replace the 56K with a 47K resistor and a 10K pot in series. Wire the pot as a variable resistor. If the pot ever opens, the bias will jump up to a high voltage and nothing will get hurt. If you need more range, use a 39K resistor and a 20K pot. Remember that is high voltage feeding the 100K. Careful If you want to play on the other side of the diode, I might try the same approach - replace the 47K with a 39K resistor and a 10 K pot in series. Or a 20K pot and 27K resistor. Or whatever pot you like and a resistor that add up to something close to 47-50K. I think that will divide againt the resistors on the AC side. If not, try adding a 5K or 10K resistor in series with the diode, between the diode and the 47K ( or whatever is there now.)That will give the 47K substitute something to divide against.

5/23/2003 5:19 AM

Enzo

Re: bias adjustment mod for B15?

Cool, your schemo saves me the trouble of getting out mine.

Either place ought to work. If you work on the 100K/56K pair, make the bottom one variable. You do not want the possibility of turning the bias off completely, so rather than replacing the 56K with a pot, I would replace it with a pot and resistor. That way if you turn the pot to zero, the resistor will still establish at least a minimum bias voltage. I would replace the 56K with a 47K resistor and a 10K pot in series. Wire the pot as a variable resistor. If the pot ever opens, the bias will jump up to a high voltage and nothing will get hurt. If you need more range, use a 39K resistor and a 20K pot. Remember that is high voltage feeding the 100K. Careful

If you want to play on the other side of the diode, I might try the same approach - replace the 47K with a 39K resistor and a 10 K pot in series. Or a 20K pot and 27K resistor. Or whatever pot you like and a resistor that add up to something close to 47-50K. I think that will divide againt the resistors on the AC side. If not, try adding a 5K or 10K resistor in series with the diode, between the diode and the 47K ( or whatever is there now.)That will give the 47K substitute something to divide against.

Replies:

Matthew D Cool. Thanks Enzo.-MD... -- 5/23/2003 2:11 PM