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 Electronics
 Electronics Repair
 Radioshack STA-720
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cirvin
Nobel Prize Winner

USA
1542 Posts

Posted - Dec 30 2005 :  01:45:18 AM  Show Profile  Send cirvin an AOL message  Reply with Quote
I have an old Radoshack STA-720 reciver that has a bad power amp on the left channel. The sound from it makes me think that the power transistor is unbiased.

What should I look for when I try and repair this? Is it more likely that the transistors are damaged or possibly the capacitors are bad?


http://i3.photobucket.com/albums/y97/cirvin/amp.jpg
^pic of the amp board, if it helps...

http://daxter12.topcities.com <Updated:July

sergiosparks
Apprentice

Philippines
132 Posts

Posted - Jan 10 2006 :  01:47:05 AM  Show Profile  Send sergiosparks an ICQ Message  Reply with Quote
hi Cirvin if the other channel is functioning properly make a voltage reading of the transistor leads and then compare it with the bad channel.I usually check the output going to the speaker and make sue that there is no DC voltage.that is if it was a briidge transformerless design.Since its an old unit replacing all the capacitors is also a time saving solution.

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cirvin
Nobel Prize Winner

USA
1542 Posts

Posted - Jan 14 2006 :  12:01:29 AM  Show Profile  Send cirvin an AOL message  Reply with Quote
Cool, thanks!

http://daxter12.topcities.com <Updated:July
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