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Placid BP Power Supply R1 smoked
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noodles  
#1 Posted : Friday, September 10, 2010 9:29:20 AM(UTC)
noodles

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Hello Brian/Russ,

I got a spark and smoke when measuring the R1 to adjust to ~ 0.25V (i think I may have come in contact with one of the QN1 transistor legs, the voltage over R1 is 0.007V and will now not bias at all. All LEDs work, and I’m still getting 15v over both rails. Both QN1 and QP3 are cold. The board was working fine, until the spark and smoke incident. Where’s the best place to troubleshoot.
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avr300  
#2 Posted : Friday, September 10, 2010 12:54:11 PM(UTC)
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See http://www.twistedpearau....aspx?g=posts&t=1180

Properly your potentiometer has lost it..
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noodles  
#3 Posted : Friday, September 10, 2010 4:20:04 PM(UTC)
noodles

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avr300, thanks for that, it has not been tested under load it may be the VR1, how do I test to make sure, it was working fine before the spark, and I did not over wind it? I got the spark from R1, I thought QN1 may be the culprit.
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noodles  
#4 Posted : Friday, September 10, 2010 9:02:41 PM(UTC)
noodles

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OK I get no resistance adjustment from VR1 when I turn the trimmer, I’ll replace it and see.
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avr300  
#5 Posted : Friday, September 10, 2010 11:54:00 PM(UTC)
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I think your probe while touching either end of R1 slipped and hit the ground plane ontop of the PCB simultaneously touching R1. If so, you will kill the pot.
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johnwmclean  
#6 Posted : Tuesday, September 14, 2010 5:16:32 AM(UTC)
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Thanks avr300, that worked a treat! Psu is up and running.
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avr300  
#7 Posted : Tuesday, September 14, 2010 7:53:28 AM(UTC)
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Applause
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Russ White  
#8 Posted : Tuesday, September 14, 2010 5:04:11 PM(UTC)
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I just have to say thanks to AVR300 for stepping in an helping out. We have the best users ever. :)
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avr300  
#9 Posted : Wednesday, September 15, 2010 4:20:37 AM(UTC)
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Anytime, Russ.
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