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Strange problem with PlacidBP
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bishopoz  
#1 Posted : Saturday, July 3, 2010 12:35:13 AM(UTC)
bishopoz

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Hi guys,

I have had a PlacidBP set to 12v powering the crossover for my active speakers. It was working fine for a number of weeks then after suddenly after being powered up for some time it would drop down to ~2v on one side. The time it takes to drop from 12v to 2v has progressively shortened so it is now almost instant. Still reads 12v with no load attached though.

Any suggestion greatly appreciated.

Thanks

Paul
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Russ White  
#2 Posted : Saturday, July 3, 2010 2:17:41 PM(UTC)
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Perhaps it not set for enough current?
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bishopoz  
#3 Posted : Sunday, July 4, 2010 1:33:02 PM(UTC)
bishopoz

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Hi Russ,

I cannot get a stable voltage measure across R1 or R13 on bad side, it moves about from a couple of mV to 19v. The good side is dead stable at 250mV across R2. Does that give any pointers?

Thanks

Paul
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Russ White  
#4 Posted : Sunday, July 4, 2010 9:44:45 PM(UTC)
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What is the voltage across C3?

250mv across R2 is OK if there is no load, but is a bit high if there is one.
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bishopoz  
#5 Posted : Monday, July 5, 2010 3:51:55 AM(UTC)
bishopoz

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Hi Russ,

C3 is ~2v, same as good side. The 250mV is without load BTW.

Have tried to understand the schematic and traced the supply from C3 to output and both channels align until c7/c8 where the good channel reads ~7v & bad ~16v. I'm guessing it would be c7 and/or corresponding IC?

Thanks for your help.

Paul
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bishopoz  
#6 Posted : Tuesday, July 13, 2010 6:10:57 AM(UTC)
bishopoz

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Hi Russ,

Any pointers on where to look? I haven't replaced any components yet as I stuffed my last placid by being too gung-ho.

Thanks

Paul
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Russ White  
#7 Posted : Tuesday, July 13, 2010 9:17:22 AM(UTC)
Russ White

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Possibly a bad current adjustment pot?
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avr300  
#8 Posted : Tuesday, July 13, 2010 12:35:20 PM(UTC)
avr300

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I would try a fixed resistor approach.
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Russ White  
#9 Posted : Tuesday, July 13, 2010 5:00:45 PM(UTC)
Russ White

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Me too :)
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