Members shawnc Posted July 24, 2006 Members Share Posted July 24, 2006 My schematic calls for a JFET to be run at 4.5volts. How do I measure this, in other words which settings do I use on my mutimeter, where do I connect it to the circuit. Note the circuit uses 100k trim pot. Thanks Link to comment Share on other sites More sharing options...
Members Sir H C Posted July 24, 2006 Members Share Posted July 24, 2006 Depends on the configuration and what is set around the device. Do you have the schematic handy that you can post? Link to comment Share on other sites More sharing options...
Members shawnc Posted July 25, 2006 Author Members Share Posted July 25, 2006 Originally posted by Sir H C Depends on the configuration and what is set around the device. Do you have the schematic handy that you can post? Here's the link to the schematic from run off groove http://www.runoffgroove.com/eighteen.html Thanks for the help, much appreciated. Shawn Link to comment Share on other sites More sharing options...
Members Sir H C Posted July 25, 2006 Members Share Posted July 25, 2006 Cool, now it is clear. Okay, if you look at the transistors, each has a 100k trim pot on the drain. You want the voltage at this node (the drain talked about in the text) to be 4.5 volts with respect to ground. Link to comment Share on other sites More sharing options...
Members shawnc Posted July 25, 2006 Author Members Share Posted July 25, 2006 Originally posted by Sir H C Cool, now it is clear. Okay, if you look at the transistors, each has a 100k trim pot on the drain. You want the voltage at this node (the drain talked about in the text) to be 4.5 volts with respect to ground. Makes perfect sense. Thanks for the info One further question if you have the time, is it normal when adjusting this trim pot to find it difficult to get the drain to 4.5 volts, I find the numbers really jump around fast and find that it likes to jump way past 4.5volts. Also should I be using a 9 volt adapter, as a battery wouldn't be a full 9volts(unless it is fresh, which I can almost never find, even new they all semm to be around 8.4-8.8 volts? Once again thanks for all the help. Shawn Link to comment Share on other sites More sharing options...
Members Sir H C Posted July 25, 2006 Members Share Posted July 25, 2006 Yeah the numbers will jump. I think that the 100k is way too big a pot to use here as with the 820 ohm resistor as the degen, you will probably be in the 3-4 k ohm range when you get 4.5 volts there. Don't worry about the 8.8 volts or whatever, either a battery or AC adaptor should be fine here, the battery will probably give a "spongier" sound as it will not be as stiff a voltage. Link to comment Share on other sites More sharing options...
Members shawnc Posted July 25, 2006 Author Members Share Posted July 25, 2006 thanks for all the help Sir HC. Much appreciated Link to comment Share on other sites More sharing options...
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