I am trying to bias my Jfets in my dr boogey down from 8.6v to 5.5 without the use of trimpots any advice?
Are you using fixed resistors? If so, try larger resistance values.
what i've done is to temporarily solder in a pot/trimpot to set the bias do the desired voltage, then unsolder the pot/trimpot, measure the resistance, then solder a equivalent fixed resistor value in its place. other than that, there are some calculations that can be done based on the particular device's Vp, Idss, etc. if you're interested in that, read up: http://www.runoffgroove.com/fetzervalve.html (http://www.runoffgroove.com/fetzervalve.html)
Quote from: ubersam on November 26, 2009, 01:04:44 AM
what i've done is to temporarily solder in a pot/trimpot to set the bias do the desired voltage, then unsolder the pot/trimpot, measure the resistance, then solder a equivalent fixed resistor value in its place. other than that, there are some calculations that can be done based on the particular device's Vp, Idss, etc. if you're interested in that, read up: http://www.runoffgroove.com/fetzervalve.html (http://www.runoffgroove.com/fetzervalve.html)
when i measure the jfet do i measure drain to source or drain to ground?
if you're referring to measuring the Vp and Idss of the JFET, here is what you'll need: http://www.runoffgroove.com/fetzervalve.html#11 (http://www.runoffgroove.com/fetzervalve.html#11)
I'd go with trimpots. Far easier than teting a bunch of JFETs and you can tweak the circuit using the best measuring device of all - your ears!
I used pots to find the value and replaced them with fixed resistors. I used pin sockets to make them easy to swap.
(http://diy-fever.com/dr_boogey/board_front.jpg)
Quote from: bancika on November 26, 2009, 06:28:47 AM
I used pots to find the value and replaced them with fixed resistors. I used pin sockets to make them easy to swap.
(http://diy-fever.com/dr_boogey/board_front.jpg)
I like how you placed the effect over a Mesa ad. Classy.