Hallo to everybody.
I know this is a question about a circuit "something" old, but is a design that I liked and I could not do, even though I bought the PCB by the EPS service, and I could not end at the time
This is the "precision power supply" which appeared in the magazine number 92 December 1982 in the English edition. On the cover reading "the power supply: 0 to 30 volts, 3 amps" and showed two high-capacity electrolytic capacitors and a toroidal transformer, on a green background.
Now, after a few years, I'm back, and I've mounted it again, but I have two doubts:
The first doubt is regarding the ammeter. The schematic indicates that it has to be of 100 microamperes, but the one I have has a full scale of 5 amps. Obviously it does not work, even moving the needle. I wonder how it could be installed in the circuit to use the calibration by P3. I know I could put in series with the load, but then I lose the calibration by P3, plus I do not know if I should put a resistor in parallel with the ammeter.
The second question is related to the total power delivered by the power source. Having three 2N3055, how is it possible that the power supply delivers only 3 amps, one for each transistor? According to the article, it is because each transistor can not dissipate more than 50W, and to obtain the maximum output voltage (35V) is recommended the use of one transistor for one ampere, to avoid exceeding those 50W.I understand that if I have a maximum voltage of 21V, I could get two amps for each transistor. Is that correct?. In addition I have cooled the transistors with a good heatsink and a fan to avoid overheating.
What do you think about this?
Thanks and regards.