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  1. L

    0-30V Stabilized Power Supply

    The MC24072 is a dual opamp configuration, it should work but its not a direct replacement part, as the pinout is different, but if you can work around this, then I'm sure you could. PS, you will loose the offset too. but not a train smash though. Thats just my opinion, perhaps wait for some ...
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    0-30V Stabilized Power Supply

    Yip, started something but have been caught at at work, need to spend some time on it.
  3. L

    0-30V Stabilized Power Supply

    Ok, thanks good advise!
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    0-30V Stabilized Power Supply

    I'm wanting to add a Fine Adjustments pots to the circuit for the vltage and current, as I find the Pots are very sensitive. I was thinking of putting a 1K Pot between P2 and R18, and P1 and the output od U1. Would this work?
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    0-30V Stabilized Power Supply

    Hi PicMaster I wasn't intending to control the PSU with a pic, but rather just use the voltages of the wiper to show where the Voltage and Current pots are situated. Eg, lets say the Vpot is set to 12 and current to 1 Amp, it would show this on the LCD, along with the realtime Volts and Amps...
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    0-30V Stabilized Power Supply

    Mmmmm Ok, the "SET" values don't look like it will work, the voltages change when circuit goes into CC. :(
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    0-30V Stabilized Power Supply

    Ok, now that I have eventually got my PSU unit working 100%, I'm wanting to build a  LCD Display for it. I'm hope to have the following displayed on it. Actual Voltage Set voltage Actual current Set current Temp of heatsink So here is my question, once calibrated, are the voltages from the...
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    0-30V Stabilized Power Supply

    Thanks for all your patient help. Tested to 3amps! all ok
  9. L

    0-30V Stabilized Power Supply

    I feel like a idiot now >:(,  you have hit the nail on the head, only one of the 2N3055 cases where connected to the +35V. Will connect both and test!
  10. L

    0-30V Stabilized Power Supply

    I have checked Emmitter voltage of the Q2 and it is same as the base voltage of the 2N3055's, when Voltage pot set to 0V as per previous post, but I will check again at say 12V. I will go through the board again with a fine tooth comb, Like I always say "if it wasn't for bad luck, I wouldn't...
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    0-30V Stabilized Power Supply

    I understand what you saying Audioguru, and thats why I'm so confused. I definately seems that the BD139 is taking all the load, hence it pops at anything over 1.5 Amps. Sorry, that was a typo, was meant to say Q2 gets warm (quick short circuit of output on a fair size heatsink), but doesn't...
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    0-30V Stabilized Power Supply

    ??? Just not winning, I happy with the voltage reg side, but I just popped another BD139 while calibrating the max current (by shorting through a multimeter), I had voltage set to about 12V-14V,  the VR3 set to min current, I shorted the output (for 1 second intervals) and slowly worked the...
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    0-30V Stabilized Power Supply

    Cool, Thanks again for all your help. I will load the circuit and let you know. Cheers
  14. L

    0-30V Stabilized Power Supply

    Ok, replaced Q3, LED problem sorted. Replaced D11. Tried 2 new 2n3055, output voltage of 0.22V with a 10K resistor across outputs. U2 output still at 0.08V? VR1 still makes not difference.
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    0-30V Stabilized Power Supply

    The 2N3055 are brand new, but will try another set. Will also replace D11. R19 and R20 are correct, I will try replace Q3 and then U3
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    0-30V Stabilized Power Supply

    Hi Hope this is what you are looking for  :-\ Voltage across C1 = 35V Base voltage on BD139 = 0.08V (same as output form U2) Collector Voltage on BD139 = 35V Emitter Voltage on BD139 = 2.055V = Base voltage on Q4 & Q5. (suspect this is a problem if I understand correctly?) Emmiter...
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    0-30V Stabilized Power Supply

    Ok, here the findings, no adjustments between measurements. U2 in+ = 35mV U2 out = 76mV Voltage Pot high  = 11.32V Voltage Pot Low = 0.9mV Voltage Pot Wiper = 1mV PSU output Voltage 2.2V unloaded, 300mV with 10K resistor across output. (electrolytic cap ? problem) VR1 still makes no...
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    0-30V Stabilized Power Supply

    Thanks for the prompt reply! So what I will do : 1 - connrect C7 2 - Check input of U2 with V Pot at min, should be 0V 3 - Check output of U2, should be +1.4V 4 - Try replacing U2 5 - Increase R17 to 68ohm (what I have on hand) Will report results shortly Thanks
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    0-30V Stabilized Power Supply

    Forgot to mention, the BD139 is on a medium size heatsink, but doesn't even have time to heat up before popping.
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    0-30V Stabilized Power Supply

    Hi Audioguru, as soon as I'm able to take 1 step forward, I have to take 2 steps back. ??? 1st some background info you may require: - Transformer is 25V AC rated 5amp continuous. - Redwire's PCB. - Your Parts listing - using the TLE2141. - 2x 2n3055 and 0.47 10W. Problems 1 - BD139 keeps...
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