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| Simple DIY Linear PSU |
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| xavier60:
--- Quote from: panoss on March 14, 2020, 05:00:41 pm --- --- Quote from: xavier60 on March 14, 2020, 04:45:04 pm ---When the Inverting input voltage is less than the Non-inverting input voltage, the output of the op-amp should go to its maximum voltage. About 1.4V less than supply voltage for the LM358. --- End quote --- RL=no load, Vpin7=8.52V Vpin8=9.69V RL=20 Ohm, Vpin5=8.13 Vpin8=9.30V RL=10 Ohm, Vpin5=7.87 Vpin8=9.04V --- End quote --- Vpin8 going from 9.69V to 9.04V means that the input voltage is dropping by a lot. |
| panoss:
--- Quote from: xavier60 on March 14, 2020, 05:05:51 pm ---No problem using a SMPS so long as the voltage is correct and holds up when loaded. The Collector of Q1 should be close to 18V? --- End quote --- RL=no load, Q1 Vc = 17.33V RL=20 Ohm, Q1 Vc = 15.22V RL=10 Ohm, Q1 Vc = 14.04V I also tried with an SMPS (12V): RL=no load, Vout=11.4V RL=20 Ohm, Vout=10.3V RL=10 Ohm, Vout=9.9V EDIT: I tried with a second SMPS (a PC power supply). The results are the same. |
| xavier60:
--- Quote from: panoss on March 14, 2020, 05:46:22 pm --- --- Quote from: xavier60 on March 14, 2020, 05:05:51 pm ---No problem using a SMPS so long as the voltage is correct and holds up when loaded. The Collector of Q1 should be close to 18V? --- End quote --- RL=no load, Q1 Vc = 17.33V RL=20 Ohm, Q1 Vc = 15.22V RL=10 Ohm, Q1 Vc = 14.04V I also tried with an SMPS (12V): RL=no load, Vout=11.4V RL=20 Ohm, Vout=10.3V RL=10 Ohm, Vout=9.9V --- End quote --- RL=10 Ohm, Q1 Vc = 14.04V, means that 4.5V is being applied to B-E of Q2 which means that it's damaged. This is assuming that the supply is holding up at 18.5V. But why was the 9V rail dropping before? Are you using an LM317? |
| panoss:
--- Quote from: xavier60 on March 14, 2020, 05:55:54 pm ---RL=10 Ohm, Q1 Vc = 14.04V, means that 4.5V is being applied to B-E of Q2 which means that it's damaged. This is assuming that the supply is holding up at 18.5V. But why was the 9V rail dropping before? Are you using an LM317? --- End quote --- Yes, I 'm using an LM317. (I just took one more look to make sure :D) I 'll replace it to be sure, maybe it 's damaged. |
| panoss:
Well, I replaced: -the S8550 with the BC557 -the LM317 with another LM317 Results are the same. |
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