iceblu3710
Member level 3

I have an awesome bench power supply from the 80's that just made a funny noise then slowly faded away. Now when I turn it on the voltage meter spikes then slowly settles and then the power LED faded off. I would love to fix it but this is a complex piece of analog circuity I can now wrap my head around!
What I would like to do is understand the system so I can make a new one out of more modern components. With the large selection of low Rds MOSFETS I can make one that puts out way less heat and has a larger voltage and current range. However step one is to figure out whats going on. I understand that node (G) outputs a voltage in proportion to the selected voltage via R2/R3 and that when the current rises above the set level the current part of the circuity will lower the voltage at node (G). With the way schematics "should" be drawn I think I can assume that everything left of Q105 handles the voltage and everything on the right handles the current. From here thought I have no idea how to start analyzing the circuit.
Anybody feeling up to a challenge and willing to help me figure things out? Thanks!

What I would like to do is understand the system so I can make a new one out of more modern components. With the large selection of low Rds MOSFETS I can make one that puts out way less heat and has a larger voltage and current range. However step one is to figure out whats going on. I understand that node (G) outputs a voltage in proportion to the selected voltage via R2/R3 and that when the current rises above the set level the current part of the circuity will lower the voltage at node (G). With the way schematics "should" be drawn I think I can assume that everything left of Q105 handles the voltage and everything on the right handles the current. From here thought I have no idea how to start analyzing the circuit.
Anybody feeling up to a challenge and willing to help me figure things out? Thanks!
