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Power supply shorting problem

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buffalo960:
Hello,

I put together this power supply a few months ago and it was working (as far as I could tell) because the LED shown in the schematic attached would light up just fine. I was having trouble getting the supply to vary. The project got put on hold for a while and I just came back to it today. Now every time I power it up I instantly get a 9ohm short between power and ground. I have replace the regulator 3 times all with the same result.

I am puzzled by this because as soon as the regulator blows out the short is gone. I only have 3 regulators left and would rather not blow them out. Does anyone have any ideas on why this would be happening? Let me know if you need more information then I have given.

I should also mention I am using the LM27342  http://cache.national.com/ds/LM/LM27341.pdf

amspire:
Where is the schottky diode from the SW pins to ground? The regulator cannot function without it. You will get the regulator IC either latching or blowing.

buffalo960:

--- Quote from: amspire on December 10, 2011, 11:30:08 pm ---Where is the schottky diode from the SW pins to ground? The regulator cannot function without it. You will get the regulator IC either latching or blowing.

--- End quote ---

Thank you for your reply. I am gunna go run to get a diode and try it out.

codeboy2k:

--- Quote from: buffalo960 on December 10, 2011, 11:34:12 pm ---
--- Quote from: amspire on December 10, 2011, 11:30:08 pm ---Where is the schottky diode from the SW pins to ground? The regulator cannot function without it. You will get the regulator IC either latching or blowing.

--- End quote ---

Thank you for your reply. I am gunna go run to get a diode and try it out.

--- End quote ---

 :o :-X

buffalo960:

--- Quote from: codeboy2k on December 11, 2011, 10:01:47 am ---
--- Quote from: buffalo960 on December 10, 2011, 11:34:12 pm ---
--- Quote from: amspire on December 10, 2011, 11:30:08 pm ---Where is the schottky diode from the SW pins to ground? The regulator cannot function without it. You will get the regulator IC either latching or blowing.

--- End quote ---

Thank you for your reply. I am gunna go run to get a diode and try it out.

--- End quote ---

 :o :-X

--- End quote ---

o_O ?

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