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Overheating 1W resistors
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JohnG  
#1 Posted : Thursday, December 29, 2016 9:51:47 PM(UTC)
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I have 2 Placid BP HD. One works fine, but on the other one the 4 1W resistors start to glow within 20 seconds. Same transformer. No load. It happens to both sides of the BP. Since I only have a few seconds, I dont get much time to measure voltages. Any recommendation on what to check to narrow down the issue? I did see that I have about 4v drop across R2

Thanks, John
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avr300  
#2 Posted : Friday, December 30, 2016 8:33:40 PM(UTC)
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Check component placement.

Also post a good shartp picture of front and backside.
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JohnG  
#3 Posted : Friday, December 30, 2016 10:04:56 PM(UTC)
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Here are the front and back. I went around the bottom to check continuity where there shouldnt be.

UserPostedImage

UserPostedImage
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avr300  
#4 Posted : Saturday, December 31, 2016 2:01:16 PM(UTC)
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Have you checked that all components are in the right spots ?
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JohnG  
#5 Posted : Friday, January 6, 2017 4:09:09 AM(UTC)
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You were spot on. I had checked all that I could see easily, but had swapped some of the NPN and PNP's. That's why both sides were off. Now its working fine. And those resistors seem to be fine after having glowed.
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avr300  
#6 Posted : Friday, January 6, 2017 2:54:01 PM(UTC)
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Cool.
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