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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Thu Jul 18, 2013 10:31 pm Post subject: Sony STR0DN1010 Works for 10 mins, then speakers screech |
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Mac, here's an interesting one for ya. This sony works perfectly for about 10 minutes, everything. Then all of a sudden like clockwork, it makes a hideous loud screech from the speakers, you cant get it to stop unless you unplug the receiver.
What could be the cause? 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Jul 18, 2013 11:07 pm Post subject: |
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Don't let the cat lay on top. It gets hot....... 
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Thu Jul 18, 2013 11:09 pm Post subject: |
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haha, I wish it were that simple. It doesn't have enough time to get hot though:P
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Jul 18, 2013 11:17 pm Post subject: |
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Ok. Usual questions.
Does the screech come through the speakers? (Just to verify)
If yes does it come through all channels?
Does it matter if there is an input or not?
Is the loudness of the screech affected by the volume control?
If you switch inputs does it change?
Will it turn off with the power button? (you indicated you had to unplug it)
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Fri Jul 19, 2013 1:30 am Post subject: |
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It comes through the front right channel only
If let alone the receiver goes into protection
It does come through the speakers
The volume does not affect it, its just loud
Input change has no effect
Didn't have time to turn it off with the power button
I think its an amplifier channel mac, seems to me O_o
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Fri Jul 19, 2013 1:44 am Post subject: |
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On the main board, locate R696 and R697. Should be near the amp transistors. Remove them both and let receiver run until you think it would of made the noise. You won't get any normal audio out of that channel. Just see if the squeel is still there or not.
I'll check back tomorrow.
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Fri Jul 19, 2013 5:36 pm Post subject: |
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Back to the original header:
Stop playing Yoko Ono and Bjork! 
that's a cool problem though, if it's an analog output stage and a DSP isn't causing this, I'd suspect an open capacitor somewhere.
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Sat Jul 20, 2013 1:27 am Post subject: |
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Bjork... Really curt? Really? I would like to continue using my ears....
...without hearing aides
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Sat Jul 20, 2013 1:33 am Post subject: |
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ok mac, I know its late, doubt we're gonna get much further on this one tonight, but....
... With those 2 resistors removed, there is no screech from the receiver anymore, but the receiver still goes into protection just as it did before I did anything.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Jul 20, 2013 1:47 am Post subject: |
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You just caught me. I was just signing off.
Ok, put those resistors back in, verify it still screeches, then locate and remove C631 (10uf/50v) and test for screech again. I will have to look up the protect disable tomorrow.
When does it go into protect? Usually when the screech starts or something else? What's the time frame for the screech and for protect?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Sat Jul 20, 2013 2:58 pm Post subject: |
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| Jeremy112 wrote: | Bjork... Really curt? Really? I would like to continue using my ears....
...without hearing aides |
I don't listen to either!!!
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Tue Jul 23, 2013 4:48 pm Post subject: |
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Mac, where is that capacitor located, I spent a good half hour this morning looking and I cant find it 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Jul 23, 2013 5:02 pm Post subject: |
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Tue Jul 23, 2013 8:43 pm Post subject: |
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ahh it's right in front of one of those STK ICs, gotcha, thanks mac, will get back to ya with the results
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Thu Jul 25, 2013 1:19 am Post subject: |
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Mac, just an update, the timeframe for the screech is about 5 minutes from power on everytime, then it goes into protect about 10-15 seconds after.
I haven't gotten to it because I'm doing yard work, something I let go a few years ago and am making up for now
Ill pull the cap now and post back with how it behaves
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Jeremy112
Joined: 28 Sep 2006
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Location: Fond du Lac, WI
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| Posted: Thu Jul 25, 2013 1:43 am Post subject: |
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ok mac, with that capacitor removed and testing the unit out again, the right channel makes no sound at all, but the front left speaker is making the noise now, and it still goes into protection shortly after. I should also note I heard a few relay clicks after it was in protection.
I'll re test again to confirm the results
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Thu Jul 25, 2013 1:52 am Post subject: |
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Yep same symptoms, only as said above comes out of left speaker this time, and I hear 3 relay clicks after it goes into protection
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Jul 25, 2013 2:23 pm Post subject: |
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WHat? Your sure no noise was coming from that FL before and now there is? Are you testing all speaker outs when it screeches? And it's definitely the FL now, right? And it was FR before, right?
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Thu Jul 25, 2013 2:42 pm Post subject: |
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yes, yes, yes, and yes, I spent quite some time testing it since its a pita to take apart. I thought it was strange that the screech moved to the left channel...
It wouldn't be one of those damn STK 350 chips causing it would it? What do those do anyway?
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macgyver655
Joined: 22 Aug 2007
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| Posted: Thu Jul 25, 2013 2:45 pm Post subject: |
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| Jeremy112 wrote: | yes, yes, yes, and yes, I spent quite some time testing it since its a pita to take apart. I thought it was strange that the screech moved to the left channel...
It wouldn't be one of those damn STK 350 chips causing it would it? What do those do anyway? |
I did not expect that either. We have been testing to try to determine if it is one of those stk's or not. Give me a half hour or so to look over the schematics.
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