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Oscillations! Linear variable PSU

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xavier60:

--- Quote from: Datguy123 on August 02, 2020, 12:03:49 pm ---


--- Quote from: xavier60 on August 01, 2020, 09:31:05 am ---For R1,2,4,5, start with 1K.

--- End quote ---

I did some calculations. The max current the power supply is capable of is 6A, and having a conservative hfe of the sziklai pair (TIP42C: 30, TIP35C: 20), Q6 would need to draw 5mA of current from R6. The voltage drop across that resistor would be 5V if it was 1k ohm, which is too much. (50V input, 45V output max). Would you then advice a lower value for R1,2,4,5?

--- End quote ---
I didnt follow all of that. Although most BJTs have much higher hFE than the specified minimum, Im not so sure about the TIP42C. That's why I settled for the D45H11. I tested a whole packet of them finding the hFE close to 200 and within a few % of each other.
Start with 1K anyway.

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