Sony Surround Receiver

Sep 29, 2006 2 Replies
F

Hi



I got this Receiver STR-DE525 surround sound unit with an unusual problem well that got me stomped



Came in indicating "protector" so I found 2 output transistors that were shorted and 1 emitter resistor open



Now the set powers on and the left channel works fine but the right channel distorts badly



I`ve esr`ed caps around the "power amp" chip (before the transistor output stage) for the front channels and found they were bad so i replaced them all to find the same problem...



The inputs of the chip are all fine (with sine wave applied) but the right output distorts... I did replace the chip and same problem lingers



please anyone who can help?


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M

My guess is you probably missed a bad resistor, probably one of those that go to the base of an output transistor. Some were 10 ohms, IIRC, some were

180 ohms. You can try measuring across the emitter-base junction of the two output transistors involved on that channel. Since the Sony uses Darlington outputs, the voltage reading should be around 1.1 volts. The lack of this base-bias on one transistor will tell you where the problem is, just trace back from the base to the bad resistor.

Mark Z.

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A

Agree with Mark 100%

Arfa

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