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Old 28th August 2012, 03:13 AM   #1
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Join Date: Jun 2012
Default ALPHASONIK PMA4075

This amp is wierd i have 10.50 volts on every leg of every single op-amp..

I have 10.50 volts on all 3 legs of every output..

Heres what i have on the 494

Pin 1:0
Pin 2:0
Pin 3:0
Pin 4:0
Pin 5:0
Pin 6:0
Pin 7:0
Pin 8:13.89
Pin 9:0
Pin 10:0
Pin 11:13.89
Pin 12:0.78
Pin 13:0.16
Pin 14:0.16
Pin 15:0.05
Pin 16:0

Any ideas?
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Old 28th August 2012, 03:32 AM   #2
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Join Date: Nov 2003
Location: Louisiana
There is likely 0v instead of 10.8v. Use one of the non-bridging speaker terminals or the secondary center-tap of the power transformer as the reference (black probe).

Pin 12 has to have at least 7v (will generally be approximately 12v) for the IC to operate. Determine why there isn't enough voltage on pin 12.
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Old 28th August 2012, 03:40 AM   #3
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Join Date: Jun 2012
Ok found a broken trace on the botton side of the board amp powers up perfectly now
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