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Old 31st July 2011, 05:39 PM   #1
aypo is offline aypo  Slovakia
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Join Date: Apr 2009
Default fixing nad c325bee

Hello all the good people, I got a broken nad c325bee and was hoping in fixing it. I would really appreciate your help.

The left channel of the amp is broken, i took out all of the power transistor as i didn't have a scope home. I found Q114 and Q113 gone. Today i got a scope from my friend so i tried to apply some sine signal to the input of the amp and checked the signal at the input part of the power amp. the signal is present there at the Q110 Q111 (they're still out) but the signal has about 20V offset which goes down to about -20V. is this happening because of those transistors still out or could there be something else wrong with the amp? i don't want to risk new transistors as it took time to get them.

any suggestions or ideas what should i check next?
all the rail voltages are ok

part of the datasheet is attached
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File Type: jpg c325beepa.jpg (193.4 KB, 43 views)
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Old 31st July 2011, 10:05 PM   #2
aypo is offline aypo  Slovakia
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Ok guys, the amp is fixed, that voltage swing caused the capacitor in that servo circuit (opamp), as it was charging the offset was changing. thnx anyway
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