Question about Sony STR-DE945 Receiver
Commonly your problem is a result in bad thermal connectivity on the power transistors.
Each power transistor is coupled to a heat sink with thermal paste / thermal conductor. When they run hot, they **** more power. There is commonly a thermistor which acts as a protection from blowing out the transistors.
There is probably a transistor that is nearing the end of its life. It will work for a while (when you power up the system) but after a couple of minutes, it starts to **** power, heat up, and trigger an thermistor up stream of the transistor, and it shuts the power stage of the amp off.
This is unfortunately a problem for a technician, or you would need to be armed with a schematic to be able to work with this problem effectively.
Posted on Mar 17, 2011
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Posted on Jan 02, 2017
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You probably have a discrete component failing inside it.
Generally speaking, an amp protects itself from heat, shorts and overloads.
Overloads can be from excessive periods of high output and shorts would be wiring issues or a speaker blowing up.
You should be able to feel if it's hot. WHY is it overheating? Make sure it has sufficient ventilation on all sides and that vent holes are not blocked by dust balls. Ensure the fan (if equipped) is running as designed (some only operate on demand). Clean dust and debris from it.
If the amp comes back on after cooling, you're lucky. They only have so many self-protection cycles in their lives so continuously resetting or cycling their power without addressing the cause can do more harm than good.
If it protects immediately on a cool power up you should disconnect the speaker connections and try it 'naked'. If it comes up then diagnose which lead(s) are shorted. If it does not come up the problem is internal and should be left to an experienced hands-on tech.
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