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Everything posted by sobol

  1. Can I increase output voltage with voltage calibration trimpot without any consequences? Or it's not recommended?
  2. I have fixed my ps, P1 was wrongly soldered. I have believed that pin order in pcb is correct... it's not. Inverting or non-inverting input?
  3. I replaced it with 3 other opamps, and the effect is still the same.
  4. Does someone have any ideas what's wrong with my circuit?
  5. TLE2141IP opamps. So... R7 looks good to me, its 0,47ohm, 10W resistor, connected from the GND "cross" on the pcb to the output GND pad. I've checked this U3 and it works in weird way. As i wrote before, voltage on the 3rd pin of U3 changes from 0 to 1,3V depending on P2 position. BUT on the 2nd pin of U3 is 20mV to 30mV (depends on P1 position), and at 30mV current limiting turns on(while P2 sets 1,3V on pin 3). That 2nd pin voltage was measured between "Cross" ground and 2nd pin. It should work as comparator, but it's not, and I don't have any idea why.
  6. Power supply is soldered on normal PCB. OK, I've made some measurements, look at the result: U1 pin 6 (output) - 11.2V. U3 pin 3 - varies from 0 to 1.3V, depends on P2 position. 10V zener diode works properly, there is 29V on emitter of Q3 while current limiter works, and 29V on pin 7 of U3. U3 pin 6 - 29V while current limiting off, -1V while current limiting on. And still power supply does not work properly. Any ideas? Can't see any bad soldering or something like that.
  7. Version from the first post (latest i believe), 28VAC transformer, TLE2141 opamps. I'll check it tomorrow and i'll post measurements. I'll focus on the U3 neighbourhood, maybe I will find a mistake. If its ok, i'm ok too. : D
  8. So, I have built that power supply, but after test run i've found what follows: P1 (voltage control pot) - without a load on the output i've got 7mV to 5V, and at maximum pot position current limiting turns on (while P2 is on the maximum, while less, current limiting is constantly turned on and output voltage is about -200mV). U1 gets too hot in my opinion - after 10 minutes of test run it was about 80-90 celsius degrees. Any ideas what could be wrong?
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