Monarch
- Thread starter Chuck D. Bones
- Start date
Chuck D. Bones
Circuit Wizard
Whoops sorry! I was using my phone to read and I missed it. Thanks. Greatly appreciated!
Chuck D. Bones
Circuit Wizard
It's all about getting the JFET biasing right. JFET circuits are not plug-n-play. Plan on selecting R4 & R12. Stock values might work, but there is no guarantee.
We're looking for around 5V on Q1-D. If it's higher than 5.5V or lower than 4.5V, then adjust R4. Increasing R4 makes Q1-D go up and vice-versa.
We want the current in Q2 to be between 1mA and 2mA. Measure the voltage on Q2-S, divide by the value of R12 and you have the current. Increase R12 to make the current lower and vice-versa.
Here's an easy trick. Assemble the board but do not solder R4 or R12. Wedge toothpicks in the 4 unsoldered holes so that the leads on R4 & R12 are held tightly in their respective holes. Power up the circuit and measure Q1-D. If it's outside the range of 4.5V to 5.5V, then remove R4 and try a different value. Use the same process for R12. Once you have the correct resistor values, solder them in.
Take your time with the build, inspect your work often making sure you installed the parts correctly and the solder joints are clean. Do a very thorough inspection and cleaning before installing the pots because once they're in, rework becomes much more difficult.
Good luck!
We're looking for around 5V on Q1-D. If it's higher than 5.5V or lower than 4.5V, then adjust R4. Increasing R4 makes Q1-D go up and vice-versa.
We want the current in Q2 to be between 1mA and 2mA. Measure the voltage on Q2-S, divide by the value of R12 and you have the current. Increase R12 to make the current lower and vice-versa.
Here's an easy trick. Assemble the board but do not solder R4 or R12. Wedge toothpicks in the 4 unsoldered holes so that the leads on R4 & R12 are held tightly in their respective holes. Power up the circuit and measure Q1-D. If it's outside the range of 4.5V to 5.5V, then remove R4 and try a different value. Use the same process for R12. Once you have the correct resistor values, solder them in.
Take your time with the build, inspect your work often making sure you installed the parts correctly and the solder joints are clean. Do a very thorough inspection and cleaning before installing the pots because once they're in, rework becomes much more difficult.
Good luck!