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Discussion Starter · #1 ·
hi i have a sony str-de725 everything is working except for the rear right channel,switched another speaker to that channel an still no sound switched speaker back n speaker works fine.have been lookn around and im thinking output transistor.??did a visiual n didn`t c any obvious blown caps fuses or resistors thanks in advance 4 any help
 

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The first thing to look carefully for are cracked solder connections. Quite common on Sony AVRs.
 

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Discussion Starter · #3 ·
:D:DThanks 4 input i did find a long burnt up solder connection.so i just soldered in a piece of wire to complete the path,now its working fine
 

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A long burned up connection sounds like a circuit trace. Very rare for that to happen as it takes a lot of current. This is the kind of thing we see on ground traces in lightning strikes.
 

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Discussion Starter · #5 ·
Well it happened again,the rear amp circuit board burnt again blowing a couple of fuses and this time taking out a power transistor with it.sony part#8-749-020-25(MN2488).I removed the rear amp board and receiver is playing ok on front channels.Should i replace the pair of power transistors(MN2488,MP1620)or just the one that blew?(MN2488)The cost is minimal about $3-$5 ea.How should i repair the board?Thanks in advance 4 help.Here r sum pics.
 

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If the transistors are shorted, change them. I would be looking for a shorted speaker wire or something else wrong in the unit with that kind of damage. Shorted transistors in these will usually shut the unit down, maybe take out a fuse, but burned traces mean something else is very wrong.
 
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