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Posts posted by WinDTrek

  1. It is difficult to set each supply to exactly the same output voltage.
    One supply might be 20.1V and the other is 20.0V.
    The one with 20.1V will power the load and the one with 20.0V will cause the driver and output transistors to exceed their maximum allowed reverse-bias emitter base voltage (5V and 7V) and break down slowly, because the opamp U2 will see that the output voltage is too high and will try to reduce it by driving the base of the driver transistor to ground. Then all 3 transistors break down.

    i see... so far i don't see any problem with my 2 x 5A supply using in parallel. previously i did connect a 2 light bulb rated at 12V 50W each to test the supply in parallel configuration and i was able to draw 8+A of current from the 2 supply (4+A each) and run that for a while good thing it did not harm or damage the 2 power supply..  one thing i noticed though was that the ammeter reading was fluctuating..i guess due to load sharing..   anyway i will not use my supply in parallel unless otherwise it's really needed... thanks for the advise guru..

  2. P.s Eagle files have problems. They dont exist in the database that you have upload.
    If it doesn't bother you can you tell me the connections of your pcb with transistors.... etc?

    P.s2 With the blue trimmers what settings can you make?

    Please check my last post, I replaced the files with screenshots as i'm having problem sharing the eagle files. In the screenshot, I think I have all the labels including from to connections. e.g. from board 1 to board 2, from board 2 to transistors... etc.. Should be easy to follow.. : 8)
  3. Actually the problem I have was when I power on my power supply LED lights up. This problem goes a way when you turn P2 1/8 clockwise. After that returning P2 while the power is still on to minimum LED remain off. The problem only occurs upon powering up the power supply. Changing the value of R7 from 33 to 56 ohm fixed the problem.  Before I'm getting 0.6mV at Pin 3 when P2 is minimum. Now I'm getting 4.5mV. In the video noticed that when I power up the power supply LED did not turn on. Maybe the one you saw was when I put load into it.

  4. My R18 is 20K with a 200K trimpot. P2 is 10K R17 is 33 ohms . Just check redwire's schematic  page 1 and values is already been changed to the values that you have specified. RV2 and Rf11 was also changed. I will replace this then and see what happens. Btw 'm using MC34071. Thanks Guru..

  5. i think i found the reason why LED lights up when power is applied to this power supply. Pin 3 of U3 is less than 5.6mV (1.2mV and 0.6mV) when P2 is at minimum position. Adjusting the P2 to 1/8 turn will give me around 5.6mV. At this position of P2 LED will not light up when power is applied. I'm thinking of replacing R17 (33 ohms) to a higher value to get 5.6mV. Also, what is the maximum voltage should i set Pin 3 of U3 to get 5A maximum?

  6. Thanks Guru. One more question, i have completed already the 5A version. I made 2 actually and put some switches to interconnect the 2 x 5A version in series (to get 60V max) or in parallel (to double the amperage). However, one thing i noticed is that when I turn on the power supply the LED of the 2 x 5Aversion will light up (P2 or the current limiter pot is at minimum position). What i do normally is rotate P2 about /8 turn clockwise and the LED will turn of. After that putting P2 back to min LED will no longer light. Is this normal?  Aside from that everything works fine. I will post some pictures later.

  7. i'm currently building the 5A version. i have all the components soldered already on the PCB. however just now i noticed that D10 is not in the schematic but it's on the part's list. i have check again the final schematic from red and audio and both has NO D10 but it's on their part's list.

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