Question about Sony STR-DE375 Receiver
Protection is usually a sign of overheating or something is wrong at the power amplifier's output.
Theory: Protection is a delay and sometimes an internal test to allow the electronics to stabilize during power up before they are allowed to interact with the speakers. The most common cause of it remaining ON is that a speaker cable pair is shorted. Some isolation is required...
1. Turn the Power OFF.
2. Disconnect each set of the speaker wires that are directly attached to the receiver. Mark them so you remember where each one went. pay special attention to which conductor is on "+" or "POS" and which is on "-", "COM" or "Ground". You may elect to disconnect them one pair at a time if your sytem is complex and you don't want to lose track of where things were.
Turn the Power ON. Is the "Protect" indication gone from the display?
If YES, you have a shorted speaker wire or speaker. To isolate the specific cause:
1. Turn the Power OFF.
2. Attach ONE speaker wire pair at a time and test it by turning the Receiver ON. When the "Protect" light returns you have isolated at least one of the cause(s). Disconnect the defective speaker cable and continue isolation of all speaker cables. Visually examine the cable at both ends for frayed wires that could touch each other or contact metal on the receiver or other objects.
To isolate further within the cable/speaker pair - disconnect the speaker end of the cable on the failing path. Try another cable that you know works, or at least one that doesn't cause Protection to stay on.
If you're electrically savvy and have a Digital Volt/Ohm Meter you can troubleshoot the short(s) with it.
If NO, there is probably an internal problem.
Is it solid or does it come on after the Receiver has been ON awhile.
It could be overheating.
Is the unit hot to the touch?
Is there a cooling device (fan)?
Is it stopped or clogged with dust?
Is there adequate ventilation around the unit for air to flow?
Clean any ventilation slots on the top and bottom of the unit.
Avoid stacking components that produce heat under an amplifier or receiver. Their heat rises. Also keep them away from other heat sources like like home heating vents and radiators.
Problem solid and NOT related to the speakers or heat: internal malfunction.
Let me know.
Posted on Apr 02, 2009
SOURCE: Sony STR-D665
Protet mode is a special diagnostic mode that starts when a fault is detected.
When in protection mode the unit is prevented from starting by protection circuit, so to prevent further damage.
Check the speakers and speakers wiring, a contact in speaker wires, or faulty speakers can send the unit in protection.
Try unplugging power cable for one hour or so. then connect cable back and see if you get rid of protect state. Sometimes accumulation of electrostatic charges inside circuit capacitors can kick in protect mode. In that case unplugging the unit from main for some times can get rid of electrostatic charges, and reset circuits by draining power completely.
If that was the problem, you will not get Protect when plugging back power cable.
If you do all the above and still get Protect, then there is a real fault.
In that case the unit may be disassembled and tested to find the fault.
If that is the case I suggest contacting the manufacturer at the number listed on the owners manual, or asking a quote on repair to a local technician.
Posted on May 29, 2009
There's a button that turns the speakers OFF right above the headphone jack.
Get the manual: retrevo.com
Posted on May 21, 2010
Testimonial: "@dunnbiker Very true on assumptions! I've tried everything the manual suggests. Right now, nothing is connected to the unit, but upon power up, I get the SP:OFF display (which is not seen in the DEMO mode). I will try the headphone jiggling idea and see what happens."
Generally speaking, an amp attempts to protect 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.
Posted on Aug 02, 2011
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