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  1. T

    0-30 Vdc Stabilized Power Supply

    I tried with a 2.7ohm 200W dummy load.I set 3A output.All transistors were quite cool.I am afraid to short the output.Another discovery: From one transistor passed 1.3A,from the other 1,1A and from the third(with 0.2ohm emmiter resistor) 0.6A.My mistake is that i measured the third transistor's ...
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    0-30 Vdc Stabilized Power Supply

    Yes,i had a wonderfull vacation thank you!I envy you audioguru.I am still a student and i have 50 years in order to become retired. I finally used 3 of them with  0.1ohm emmiter resistor at 2 of them and 0.2ohm at the third one  in order to match them.What i did is ok?With a fan blowing them...
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    0-30 Vdc Stabilized Power Supply

    Hi all!I am back from my vacations!One more question: Can i put 3 or 4 paralleled 2n3055 transistors just to be on the safe side?
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    0-30 Vdc Stabilized Power Supply

    Both transistors are from toshiba.Oh well...I will buy new ones. ::)
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    0-30 Vdc Stabilized Power Supply

    I measured the voltage drop across the emitters 0.1ohm resistanse(2A output).I measured 0.012V and 0.188V , which means from one transistor passes 1.88A and from the other 120mA !Is it strange such a difference?
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    0-30 Vdc Stabilized Power Supply

    I changed the 2n3055's.Now everything is fine :I checked the voltages you mentioned and they are ok,I put the 2 transistors in the same heatsink(I forgot to buy another one  :-\ ,tomorrow i will) using thermal grease and a 12V pc case fan..Everything seems fine and i am currently testing the psu...
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    0-30 Vdc Stabilized Power Supply

    So... Fan it is then!  ;D
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    0-30 Vdc Stabilized Power Supply

    Audioguru what size do you suggest for the heatsink? 
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    0-30 Vdc Stabilized Power Supply

    Another question if someone puts maximum V and A and shortcircuits the output what will happen?
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    0-30 Vdc Stabilized Power Supply

    Well...end of fun for today.Q4 damaged!I used a quite large heatsink for Q4(with mika insulators) but it became really hot during tests(i could barelly touch the heatsink which was 15x10cm).Q2 was all the time cool, it did not heat up(4x2cm heatsink). I didn't use thermal grease.I will do volt...
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    0-30 Vdc Stabilized Power Supply

    I forgot to mention that if i set volt and current pots so as the current limiter is not on, after a while amps jump at 5A and the led turns on. :-\ :-\ :-\
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    0-30 Vdc Stabilized Power Supply

    I found a 2.7Ohm 25W resistor.I connect it at the power supply,I put the volt pot at max and played with the current regulator.In the beginning everything is ok but after a while something happens and output jumps at about 5A,if i set high amps it jumps after a second or so(with lower amps...
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    0-30 Vdc Stabilized Power Supply

    Ok, i will use my sound card as an oscilloscope.In a couple of days i will hit the shop to buy some resistors to construct a voltage divider first(I think my soundblaster will burn if i give it 30V input :P ).
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    0-30 Vdc Stabilized Power Supply

    ;D Of course i will test the psu and make a post.I have a dmm [a scope is a bit expensive for me :( (can i use my sound card as an osciloscope?)].I think it is accurate(0.5% accuracy in Vdc , 2% measuring Amperes). What measurements should i execute?
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    0-30 Vdc Stabilized Power Supply

    Audioguru you are trully a guru!Thank you!Q2 was wrongly soldered i changed emmiter-collector and the psu works great now!Everything works!Output voltage is ok so as the current limiter!!!Q2 was indeed destroyed but fortunately i had a spare tip31c.U2 was also a bit hot before but i could touch...
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    0-30 Vdc Stabilized Power Supply

    I replaced the 2n3055.Now the its varies fron18.1 to 31 volts but now it is proportional to the volt pot.By turning the volt pot from max output to minimum,the voltage drops until halfway of the pots turning ability,and after halfway it remains steady at 18V.Now to your questions: 1)Yes 2)It...
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    0-30 Vdc Stabilized Power Supply

    Audioguru thanks a lot but before i do anything i just discovered that the 2 2n3055 are probably burned and they need replacement(strange they didn't smell bad...LOL).The collector of 2n3055 is its case right?I will check what you have told me right after.Thanks again for your patience.
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    0-30 Vdc Stabilized Power Supply

    The voltage of pin 4 of U2 is -5.58V without load and with load, with current limiting on it is -4.35V.should i measure the voltage at the transistors?
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    0-30 Vdc Stabilized Power Supply

    with 30ohm load and pot set to 30v the output voltage is 0.81V(without  load it is 31V)  .With the volt pot set at min output voltage(with load) is 0.5V(without  load it is 19V) .By turning a bit the volt pot it jumps instantly at 0.81v and stays there independently from the pot(without load...
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    0-30 Vdc Stabilized Power Supply

    I measured the volt pot and it is ok.the other pot varies from 0v to 1.6v . When i connect a 30 ohm load the out put voltage drops (without current limitation) and varies from 0.5 to 0.8v . ??? ??? ??? :-\Current limiting also seems erratic.
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