Question about Sony STR-DE505 Receiver

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Sony STR-DE505 Not working

I have a Sony STR-DE505 that powers up normally, but then displays Protection on the LED display. What do you think the problem might be. I have read in other forums that it might be an audio outputage problem or a Power supply issue, but im not sure which way to go. Can you help me? Thanks for your time!

Terrence Jones

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  • 3 more comments 
  • Terrence  Jones
    Terrence Jones Jan 05, 2009

    I am a little knowledgable about electronics, but need help on which parts I need to test.

  • Terrence  Jones
    Terrence Jones Jan 06, 2009

    I have found the Power Amp Drivers. They had poor solder joints, so I reflowed the solder joints and the Reciever worked with a video input and output (into a TV) for about 20 mins. I noticed by touch that the Power Amp Drivers were extremely hot. I have purchased new Power Amp Drivers (NEC IC 15-PIN V-DIP UPC2581V) and I will see if this corrects the problem. Thanks for your help. I will let you know how everything turns out.

  • Terrence  Jones
    Terrence Jones Jan 06, 2009

    I have gotten one. I will replace those IC's and see if it help. Do you think the problem is with the IC's overheating or that they were damaged from previous overheating?

  • Shahid Electronics
    Shahid Electronics May 11, 2010

    I would recommend to get related service manual form any online store to see schematics as well.

  • Shahid Electronics
    Shahid Electronics May 11, 2010

    Protect message is sign of problem in amp out stage and required output parts to be checked and replaced accordingly.
    Do you have electronics knowledge and repair experience  to provide you more tech details.

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1 Answer

My Sony STR-DE185 is displaying "PROTECT". The manual says it is from a short circuit. Are there any known common problems with this unit related to short circuiting? Mike


If the speaker wires shorted together, it will trigger the protection circuit. If the output transistors/IC shorted out in the power amplifier section, it will also go into protection mode also.
Try disconnecting all the speaker wires to see if it will come on normal.
to have it fixed by the shop may not be worth it.

Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors pictures: http://s807.photobucket.com/albums/yy352/budm

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1 Answer

Hai.i have a sony str-de505 amp. one day i put the volume high n on the unit.suddently the sound goes high n then no more produsesing a single sound.when i switch on the souround n on the uni,the sound...


You cooked it. Maybe you lucked out and just blew a speaker.

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.

Check for loose speaker connections at the speaker as a root cause for intermittent shutdown.

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3 Answers

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Hello
Check the input fuse first. If it is blown, there will be some short inside the power regulator circuit. Usually Sony sets uses STR regulated power supply. You can see this STR, and Ic, screwed onto a heatsink. Replace it with a same type and number. Before replacing the STR, check the diodes used in that section for damage, mainlu zener diodes. They might get shorted along the blowing of the STR. Check that section throughly before resoldering the new STR.
If any further assistance you needs, get me through Fixya. Ok.

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The reason this happens is because it takes about 3 to 5 sec. for the output circuit relay to kick in after power up, im sure at this point is when your receiver shuts off and flashes red. You have a bad output Transister its shorted to ground and the sony's protection circuit kicks in and shuts it down. Unless you are a electronic Tech. you will have to take it in to be repaired its going to be about 120 dollars to repair. Now im assuming your speakers are ok, if you have them hooked up when you do this try disconnecting them and try to power up if it does you have a shorted speaker, but normally Sony just displays overload protection on the display. Im sure you have a shorted Trans. sorry for the bad news good luck.

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Do you hear any clicks? If not, the standby transformer or related circuitry is bad. If you hear 1 relay click...the audio output section is most likely the problem. The first click you hear is the main power relay...and should see display.. the second relay click is the protection circuit relay engaging to let audio to your speakers...if the second click is not heard (it should occur in 3 to 5 seconds) there are shorted output transistors or a shorted output IC trying to blow your speakers with 50 to 75 volts dc. The protection circuit monitors the speaker lines for voltage. They should always read milli-volts only...not even 1 volt.Anyway, good luck

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