Question about Sony STR-DE425 Receiver
You may have loosened a solder joint on one of the components inside with your air blast. A repair tech would monitor the outputs DC offset voltage and he will probably see one that is not zero volts and while wiggling various things he should see a sudden change in the DC offset voltage on the bad channel when he touches the bad connection. Then it's just a matter of resoldering the connection. Good luck on this one.
Posted on May 02, 2007
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Posted on Jan 02, 2017
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It is possible that the amplifier had encountered a fault with a higher current drain which had triggered it to a protection fault condition. The fault can be with your output drivers. Please check for short on the outputs fitted for both the channels. Use a meter after disconnecting to check for short in the drivers. Disconnect the positive and negative voltages to the output and see if the protect changes. Even a fault in the preamp stages that drives in high current into the output can shut the Amplifier. Sometimes this can be a noise which can be a HUM or HISS before the protect works. Faulty capacitors in these circuits also can cause similar issues and needs close observation.You need to confirm and replace the specific stages or outputs. If not there can be issues in the mother board. Maybe the protect circuit by itself is shutting off due to a faulty bias or there is a leak in any voltage/current sensing circuit. Also disconnect the speakers and test, if the amplifier comes out of the protect mode then check for short on the speakers.
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Generally speaking, an amp protects itself from heat, shorts, overloads and operator exuberance by refusing to turn on or stay on.
Overloads can be from excessive periods of high output or marginally low impedance loading by the speakers; 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 and competent hands-on tech.
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