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Tristable

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Everything posted by Tristable

  1. Hi! When I buy proper heatsink I will test PS for a longer period and then report. It's robust, it will keep it up. ::) And a question about measuring output current as voltage over R7: wont R7s tolerance and temperature change ruin correct reading? Thanks, Triple
  2. Hi! Yes, you're absolutely right! My power supply is working! :D Yes, you were right about that too. My apologies that I claimed contrary. What else to say... Everything is working fine, just one thing I don't understand: I have exactly 30,8 VDC and 3,08 ADC at max setting over 10 Ohm resistor, but I have only 100VA transformer. ??? And, of course, big big thanks to designer of this circuit, everyone who helped with it's modification, and especialy Mr. Audioguru for doing such a great job. Thank you.
  3. Hello, it's me again. I've replaced burned output transistor with 2 new ones. I still belive that current regulation is not working, because load isn't reacting on pot 2 changing no mather how, just, like I said before, only drops the voltage down and turns the LED on at max setting. Can you please give me some advices or measuring points to check this out? Or, could it be something else wrong? Please, help me! Thanks, Triple.
  4. Hi! Well, then allright. No problem, I will fix this as soon as I get. Thank you!
  5. Everybody, Hello! I'm building power supply from this great community. (looks familiar?) And yeah, I want to add this meters in my PS. So, I have 2 questions: 1. As I need only measuring positive voltages, I will use just positive 5V supply. And as my meter will be set on 0-200V range (with 0.1 V precision), and as I do not need negative sign, can I just remove one 7-seg. display - it would be off anyway? Of course, brightness resistor would be bigger. 2. Is original PCB layout OK? I hope that one who made Eagle layout is not angry, I appriciate his effort, but I realy dont like boards with askew components. ::) Well, maybe I remove negative voltage generator and make this resistors straight. Thanks, Triple
  6. Hello, Audioguru! Thanks for answering. OK, maybee I'm just care to much about opamps. I have to recalibrate my heat sense. ;D My mistake. I was thinking on R4. It's 1k. I built PS regarding to modified list (just used a 100 VA trafo, BD243C as Q1 and Q2, and BZX85C instead BZX79C), so all other values are like on mod. list, including R4. And referent voltage is 10,9V. I will try to get BZX79C, but they would give it to me if they had, so I doubt. To drop R4 more? I reversed it and then output transistor burned. I know, I should use two of them. Now I can buy other one (two) in Monday, not before. :( Before I reversed it, I runed some tests with bulbs. But they aren't reacting on current pot no mather how I turn it. Except on max setting, when current limiter drops voltage on 0.something volts and bulb shuts down. So, I still think that current regulation is not working. But, however, now I can't do anything without power transistor before Monday (or can I?), so I have another question (idea)? Of course, if You can and want help me... Hope i'm not to annoying. What about nice digital controls instead unprecise pot's? Or just as addition for precise setting. I searched this forum and google, but I didn't found anything to satisfy me. ;D Cause I want dirty, cheap solution without microcontrollers, damn expensive IC's... Just simple plug&play 8) . I see that You are real master here, so maybe you have a solution? Thanks, Triple
  7. Audioguru, hi! Thanks for your answer. I don't know about opamps, but they seem to warm to me. I ckecked some things once again, and I've done some measurments. So far, here are the results: All transistors are OK - not burnt and correctly connected I was checking voltage refernece and found that I changed R14, but I didn't had BZX79C so I used BZX85C (45mA) - I readed about this modification - something serious? Some numbers: At pin 6 of U1 there is 10,9 V At pin 3 of U2 voltage varies from 0 - 10,6 V as changing P1 And on pin 6 from 0 - 34,1 V Also, I did some tests with loaded PS. Well, voltage regulation is realy nice, but current regulation... I was testing with LED and small DC motor. They do not react on rotating P2. Only when I turn it to max, then current limiter LED comes up and voltage drops a lot. Can you said something from this data, or give some more measurments to preform? Thanks, Triple
  8. Community, Hi! ;) I would need your help. I'm not realy total newbie, rather a electronics student [newbie] ;D. Ok, lets get serious now. Of course, I built this power supply. (modified 3A version, 30V trafo, OPA445's, 10000 uF cap. ...) And also there is a 'little' problem... Voltage regulation works very nice, smooth, from 0.0 V to 33.3 V. But, temperature of U1 and U2 rises and after 30 sec i turn off power supply. (I realy care for my OPA's :P). Also, R1 gets warm althrough it's 5W. Btw. current pot. at testing is set somewhere in middle. I dont know if current setting and limiter are working, have not tested PS with load. I hope that someone can help me. And I know that my english is far from perfect... Sorry... Modify: That's when you're posting in hurry... I forgot one, maybe important thing; when PS is turned of U2 temp. quickly raises a lot... Thats it. Triple
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