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sony STR-DE345 receiver displays protect

cjdtech

Apr 10, 2010
1
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Apr 10, 2010
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1
hello-- i have a sony STR-DE345 receiver that displays protect when turning on--
even with all speakers and inputs are disconnected upon disassembly nothing appears to be burned---
just found and printed the service manual and have a dvom---
looking for advice--what to check? what is the most common cause of this failure??
any help would be greatly appreciated
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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You should probably start by ensuring that the power supply is working
 

jerryg50

Apr 18, 2010
57
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Apr 18, 2010
Messages
57
hello-- i have a sony STR-DE345 receiver that displays protect when turning on--
even with all speakers and inputs are disconnected upon disassembly nothing appears to be burned---
just found and printed the service manual and have a dvom---
looking for advice--what to check? what is the most common cause of this failure??
any help would be greatly appreciated

Some years ago, I used to service similar receivers to yours. It was very common the output transistors and drivers would fail, and have to be replaced. Many of the newer models of these receivers and amplifiers are using output IC devices. In theory, what I am about to explain will apply to both types.

Along with the output devices some of the support components will have to be changed if they were damaged. Sometimes, the bias resistors to the output transistors would have to also be changed.

The main causes of failures are if the speaker wires were shorted, or if too many speakers are connected at the same time on each of the channel outputs, or if the transistors lost proper thermo contact to their respective heat-sinks and over heated, or the users played the unit much too loud and the output stage become overheated.

If you replace all the defective parts that you can find and you missed some other part that is defective, as soon as you turn on the power you can damage the newly installed parts. Then you must start all over again.


Jerry G.
 
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