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fikic

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Everything posted by fikic

  1. Somewhere in this topic, somebody said, that some capacitor must be changed from electrolytic to tantal or something. Try to browse a little.
  2. So, I need at least 28V 120VA transformer? But output with 28V or 30V transformer has also hum at maximum output voltage, yes?
  3. With this hum, you mean just noise, or it has impact on quality of output?
  4. My transformer is 250VA, so current isn't the problem. So 24V output is just fine?
  5. No, I have 3A version with 24V AC toroid transformer.
  6. I changed output transistors and it works. I get maximum 24V on output. Is this ok?
  7. Ok, so Ohm-meter must show nothing between collector and emmitter of 2n3055, becouse it's infinite resistance? Mine show something between 100 and 200 kOhm (on both of them, on one even less).
  8. I replaced BD139 with BD135, becouse I don't have any BD139 left. Is this ok? How can I check 2N3055 transistors - I don't have transistor tester. Should one conduct between base and emmiter and between collector and emittor? If not, where it should?
  9. Hy guys. I've made a little mistake, when I connected a diode bridge. I accidentally swapped - and AC connector. I then saw some smoke and litle bang. On the output of psu, I now only get constant 33V and I can't regulate it. I thought, that opamps may be the reason and I replaced them, but this is not the case. So, what should I check next. What could happen in that case, when you swap - and AC of rectifier. PS.: PSU worked perfect before that.
  10. audioguru says, that he doesn't use Eagle..so I doubt that it is his..
  11. Your PCB is very negligent drawn.. Don't use autorouter, where you can draw PCB on your own. This one is really easy, especially if you have double-sided board like you..Just for an advice, your PCB could be much smaller for double-sided board, and much more accurate..
  12. It is normal..when the LED is on, your output voltage on PSU should drop. But try it with a bulb or something that has a constant current consumption..
  13. @audioguru, thank you for all of your help. I replaced D5 and D6 and PSU works perfect! Current regulation works and everything is fine! Thank you hundred times for your help. :-*
  14. PCB is not Eagle, it's Kicad..I will send you pdf..
  15. Ok, I replaced D7 (two diodes) and it doesn't make any difference, so this is not the case. Diodes are fine. Voltage drop across both of them is just about 400mV. ??? Can you pleeeeease take a look at my schematic and PCB, becouse I don't see any mistake now..please.. dokumentacija.zip
  16. Please look at my post again, I edited it and you replied faster..
  17. audioguru, I mounted transistors on heatsink and tryed PSU. I shorted its output and measure current. At voltage set to 30V and current regulation pot set to highest value, I calibrated it to max current 3A. But when I get near the minimum setting of current adjustment pot, it took about 5-10A. I quickly powered it off to prevent any damage. Why is that? Current regulation doesn't work fine. At highest value of current adjustment pot, I measured 3A, then I was slowly turning it down. Current was always not less than 2,96A at same voltage (30V). But when I got near minimum, LED turned on and that happend (5-10V). What could be wrong with my current regulation? PS.: I forgot to mention, that I used 25k for RV2 instead of 20k...does this makes any difference? PPS.: We talked about D8, if you remember. I used BZX85C instead of BZX79C and you said that BZX85C regulates porely. I don't have BZX79C, but I have BZX55C. Can I use it? PPPS.: Is it possible, that one of D7 diodes in series is faulted, becouse voltage drop across theese two is just 400mv..(they are not shorted, I checked)...
  18. You didn't understand me. At P2 minimum pin 2 of U3 is 45.5mV, at its maximum pin 2 of U3 is 95.5mV. Anyway, Too high...
  19. The voltage drop across R7 is just 5mV. 95mV voltage drop is just on pin 2 of U3.
  20. P2 is connected ok. When P2 is at it's minimum, the voltage on pin 3 of U3 is 15.05mV, at it's maximum it's 2.07V. Is that normal? At P2 minimum, the voltage on pin 2 of U3 is 45.5mV, at it's maximum is 95.5mV. So there is voltage drop on R7 in any case. Why is that? PS.: Is normal, that when I connect a load on PSU, just Q4 and Q5 get warm, Q2 is like nothing is on it..
  21. Thank you audioguru, I am closer now. I figured out, that I turned Q3 backwards. But still, it doesn't work perfect. At current adjustment pot turned to lowest value, LED is not on. It turns on somewhere on the end of turn of current adjustment pot. Voltage of pin 6 is 28V, when LED is not on. When it turns on, it falls to 13-10V. Pin 7 is always 24V or higher. All pins of U3 are ok. The LED is turning on with unknown reason. The voltages on U3 changes like I said with changing value of current adjustment pot. What do you say? Could be Q3 fault? PS.: all measurements applies to NO LOAD..
  22. All this I wrote applies to the case, when I have no load on output...
  23. I made a mistake when I was drawing schematic. I didn't connect - of C1 to gnd. I corrected PCB now, and PSU works when I connect a load. But only in some cases, when I turn pot for current regulation, the voltage drops. LED is still on the whole time. Now the voltage on output of U3 is 24V but not all the time. In some cases it's 17V when I turn current adjustment pot. sch.pdf
  24. Yes, it has and if I connect a load on it the voltage drops unnormally and there is no power. What could it be?
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