Question about Sony STR-DE485 Receiver
Please see the link and try it first
If the problem still there, unplug the power and open the cover. Remove the vertical circuit board in the center which has two big (15 pin) ICs on it (these are the two output amplifiers to speakers, if something wrong with them the unit will get into protecting mode). You need to unscrew the holder from the back and unlock two plastic connector to the mother board. Plug in power and turn it on, if the Portect flashing is gone, you need to replace these two ic( STK350-030 from http://www.mcmelectronics.com/product/STK350-030 )
Posted on Aug 26, 2008
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
You have a problem in the main power supply or the output circuit in this reciver. If you have any solid state repair experience, go inside and unsolder or take out the main output devices, and try to turn on the unit. If it still does not come on, your going to need to troubleshoot the power supply. If it does come on then the output devices you took out are bad. If you have no training in this stuff, seek out a pro to assist you in this repair. There are no user replaceable parts inside these units. Good Luck
Posted on Dec 28, 2006
SOURCE: flashes "protect"
I had the same problem. It's a voltage regulator (maybe 7812 or 7912)
problem. In my case the problem was cracked soldering joints on the
little PCB where the IC was soldered. Try this: open the case; on the
sides of the big heatsink are attacched 2 IC Voltage Regulators. Check
these ones for properly solder. After that I can power up my amp
Posted on May 27, 2009
The most common problem found on FixYa for Audio Video Receiver's is:
My receiver say's "Protect" or turns on then off. What's wrong? Seven times out of ten it is a shorted speaker or speaker wire. To determine your exact problem, the first step is to disconnect all speaker wires "at your receiver" Next: Turn the receiver back on. If your receiver still says "protect" or turns off, it needs to be serviced. If your receiver stays on; reconnect your speakers one at a time and power back up after each speaker. You may find that after reconnecting all speaker wires it works! Most commonly the small braids of wire from the + to the - have touched and have caused the problem. In some instances, you noticed the problem only when turning the volume up. either way, make sure the exposed wires to your receiver are no longer than 1/2" long and are completely under the screw down terminal or slide in. When you've found the wire or speaker with the problem, your receiver will go back into "protect" At this point, disconnect the wire from the speaker at the speaker that may be causing the problem then test again.* Note* Make sure speaker wires do Not touch each other as this Will cause a short! If you turn the receiver back on and it stays on, you now know the problem is in your speaker itself. To test your speaker, you will need a multimeter. Set it to ohms resistance and touch the speaker terminals, if there is a short internally the meter will read "1......" If it's an analog meter, it will peg to the right. There's your problem. Now, within any speaker there are quite a few possibilities as to what could be causing the problem. Most common is a blown coil and the speaker needs to be replaced. Some speakers have internal crossovers (usually floor standing speakers) and may have a shorted or burnt board (usually very visible brown burn marks on the board) and can possibly be repaired if your handy with a soldering iron. Now, if you disconnect the speaker wire at the speaker and it still says "protect" Check your wire for the obvious cut or nail thru the wire if possible. If your system has wiring that runs behind walls, you may need to use your meter again. Disconnect the wire at both ends, keep the ends separated, put your meter on ohms resistance and touch probes to the + and - wires at one side. If the meter pegs to the right or reads "1...." the wire is shorted and needs to be replaced or repaired at the short. Hope this helps.
Posted on Jun 07, 2010
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