# Sony STR-K502P no output on center channel



## Deucalion29710 (Apr 21, 2013)

I have a Sony STR-K502P home receiver. While watching a program the other day the center channel stopped working. Prior to that I had recently noticed a clicking noise like a relay switching off and right back on. I am assuming this was one of the blue rectangular relays on the main board. I have taken it apart a couple of times since and resoldered some cold joints but nothing seems to have done the trick. I also placed a non conductive thin layer of foam underneath the main board just in case it was a grounding issue. Should I replace the center channel relay? How do I determine which one is for the center channel and a part number for it. I also read in a forum that my output transistors could be bad. There are 2 for each channel. Again, which ones are for the center channel and how can I get a rating or a part number?


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## 8086 (Aug 4, 2009)

The Sony STR-K502P is a fairly old low end unit any repairs on it will cost more than a modern replacement. I would suggest getting a New Yamaha, Denon, Marantz, Pioneer _ELITE_ or Harman-Kardon. Any one of those will give you a massive improvement in audio quality over your STR-K502P. 

But before you spend any $$$, I would check the settings inside the receiver, make sure your inputs are set to 5.1, and double check your wiring connections. Also make sure your source material supports 5.1. Some TV programming will switch from 5.1 to 2.0 during commercials.


http://www.accessories4less.com/mak...-Network-Home-Theater-Receiver/Speaker/1.html


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## lcaillo (May 2, 2006)

Bad solder connections are very common in sony receivers. Id also make sure you dont have a problem with connections to the unit.


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## Deucalion29710 (Apr 21, 2013)

Thanks for the replacement suggestions but at this time I am seeking a relatively inexpensive repair. Just did replace my big screen. Both Sony and Onkyo were known for cold solder points. The no output on center channel seems to be common with Sony, Onkyo, and Yamaha units. Does anybody here really know the anatomy of these units so that I can get headed in the right direction? Honestly I asked some very specific questions in my original post. I already know how to dispose of electronics.:scratch:


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## Tonto (Jun 30, 2007)

Well I'm no help with that. But did you hook up the center speaker to another channel to make sure it is not the speaker or wire? May be a dumb question, but it is what I would try first.


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## Deucalion29710 (Apr 21, 2013)

Yes the first thing I tested was the speaker and speaker wire. I also tested my av input just to make sure that it wasn't my optical cable or input. It is without a shadow of a doubt an internal issue with the center channel, and being that I was hearing the relay shut off and on prior my guess would be the relay itself or the corresponding output transistors. Anybody have any thoughts on which ones they are and what suitable replacement parts may be used?


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## Deucalion29710 (Apr 21, 2013)

Also I know for a fact that this is not a settings issue as I have had my receiver for a very long time and I am familiar with its functions and I know what to expect when it decodes Dolby or DTS. All of the other speakers and the sub function as normal but there is no dialog heard as it comes through the center channel while decoding 5.1 modes.


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## Deucalion29710 (Apr 21, 2013)

Update: I found that IC401 has no solder on the #8 pin. Is this normal? Never been soldered.


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## 8086 (Aug 4, 2009)

The schematics or service manual for your receiver should available online. The IC401 appears to be a MOSFET, I assume there is more than one present in that receiver. Look and see if you spot any others like it.

But personally, I'd rather get a used Onkyo or Integra off ebay for $50 and be done; it would probably be easier than fixing an older budget oriented Sony.


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## Deucalion29710 (Apr 21, 2013)

Yeah I have been looking at them but it's a nightmare to shop for that kind of thing on Ebay. It has to have about the same inputs, wattage, and impedance. Most of those sellers are really dumb about how they list things. 90% of them do not include a photo of the back of the units showing the inputs. Most of them only have one optical if at all. I have been kind of looking for an excuse to buy one that is fully HDMI capable, but it would have to be a 5.1 and it would have to support 8 Ohm speakers.


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## tonyvdb (Sep 5, 2007)

How much is your budget. This Onkyo 609 has gotten very good reviews and is a really good deal. It was bench tested and does 90watts per channel all channels driven without distortion into 8ohms. It also has all the inputs you will need.


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## 8086 (Aug 4, 2009)

Deucalion29710 said:


> Yeah I have been looking at them but it's a nightmare to shop for that kind of thing on Ebay. It has to have about the same inputs, wattage, and impedance. Most of those sellers are really dumb about how they list things. 90% of them do not include a photo of the back of the units showing the inputs. Most of them only have one optical if at all. I have been kind of looking for an excuse to buy one that is fully HDMI capable, but it would have to be a 5.1 and it would have to support 8 Ohm speakers.


Google the model number and search google images, you will find them. As for wattage, it should not matter as long as you exceed the wattage of your Sony. All modern receivers made since the 70s can handle 8 ohm speakers, which is almost the de facto speaker impedance. Impedance is not much of a concern here unless your Sony speakers are 4Ω. Inputs don't have to match your Sony back panel, they just have to meet your needs. 

As for suggestions, Integra DTR-5.5 or DTR 6.5 or TX-SR605. The Integra DTR-7.6 has HDMI.


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## Deucalion29710 (Apr 21, 2013)

Yeah I was gonna say that Sony had those little passive 4 Ohm systems and it seems they had a couple of 6 Ohm models. I will NOT be buying another Sony though as this is my third Sony and the only one that really lasted any ammount of time. Honestly Id' like to come off as inexpensive as possible because I just had to replace a big screen and those are not cheap (a good one at least). Anyway a HDMI model would be great because I could eliminate the opticals.My sis has had good luck with her Onkyo. I have heard wonderful things about Denon. Mixed reviews about Yamaha. What are you guys' thoughts?


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## tonyvdb (Sep 5, 2007)

That Onkyo 609 that I linked to above is a great deal if your budget is small there is nothing on the market that can touch it even costing twice as much.


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## Deucalion29710 (Apr 21, 2013)

I'm really looking for a 5.1 model. It's a small room. Also I wouldn't have to buy any additional speakers.


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## 8086 (Aug 4, 2009)

Deucalion29710 said:


> Yeah I was gonna say that Sony had those little passive 4 Ohm systems and it seems they had a couple of 6 Ohm models. I will NOT be buying another Sony though as this is my third Sony and the only one that really lasted any ammount of time. Honestly Id' like to come off as inexpensive as possible because I just had to replace a big screen and those are not cheap (a good one at least). Anyway a HDMI model would be great because I could eliminate the opticals.My sis has had good luck with her Onkyo. I have heard wonderful things about Denon. Mixed reviews about Yamaha. What are you guys' thoughts?


Rule of thumb is Sony is better for Video products than audio with a few exceptions for some of their Sony ES products (source players and some speakers/headphones). Yamaha's are great, consider one of their Cheaper models from the Adventage lineup. 



Deucalion29710 said:


> I'm really looking for a 5.1 model. It's a small room. Also I wouldn't have to buy any additional speakers.



The Onkyo HT-S9400 is a good deal right now and it's got better speakers than your Sony and it includes a new receiver with HDMI. You'll be blown away.

http://www.accessories4less.com/index.php?page=item&id=ONKHTS9400&gclid=CIL1l5id37YCFUff4AodOEsAFA


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## tonyvdb (Sep 5, 2007)

Deucalion29710 said:


> I'm really looking for a 5.1 model. It's a small room. Also I wouldn't have to buy any additional speakers.


You simply dont use the additional 2 channels its not at all mandatory to use them. You wont find a 5.1 receiver with that kind of feature set.


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## 8086 (Aug 4, 2009)

tonyvdb said:


> You simply dont use the additional 2 channels its not at all mandatory to use them. You wont find a 5.1 receiver with that kind of feature set.


Outputs are a lot like inputs, use the ones you need and ignore the ones you won't be using (till you need them).


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## Deucalion29710 (Apr 21, 2013)

OK. I have never owned a 7.1. By simply not using the other 2 surrounds, does it not take away from certain ranges and effects? I'm looking a a few Onkyo models and where my Sony says that it's 500 watt, these Onkyo models seem to be 325 at most. HDMI would not be a necessity but would be nice. The only input devices on the setup is a PS3 and a DISH duo HD receiver. Both do have optical outs. I would rather not replace the speakers because I have not long been remodeled the house and installed everything in that room. My speaker mounts are kind of a pain in the butt. I just want something that has similar specs but a much better brand. DTS is important. Sony really has gone downhill . I know people who have used their service agreements to repair their Sony TVs so many times that it forced replacements. A PS3 only has an average life of about 9 months. I sure have had some aweful luck with their sub-standard receivers.


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## tonyvdb (Sep 5, 2007)

Deucalion29710 said:


> OK. I have never owned a 7.1. By simply not using the other 2 surrounds, does it not take away from certain ranges and effects? I'm looking a a few Onkyo models and where my Sony says that it's 500 watt, these Onkyo models seem to be 325 at most. HDMI would not be a necessity but would be nice.


No, you wont loose anything at all by only just using 5.1 on a 7.1 ch receiver. There are many movies now that have 7.1 channels of audio (bluray only) but if your only using 5.1 channels everything will be in those 5.1 channels.
the Onkyo 609 is way more powerful than the Sony, Its rated at 770watts. The Sony you have now at best will only do 400watts 
HDMI is a must now a days as any sort of analog video signal is being phased out to prevent copying and to standardize. And to receive the uncompressed audio formats 1080p or 3D you must use HDMI.


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## lcaillo (May 2, 2006)

Actually, not using the extra 2 channels on a 7.1 receiver makes more current available to the channels that are running. The same power supply is driving 5 or 7 channels. More channels driven, more load on the PS.


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## Deucalion29710 (Apr 21, 2013)

tonyvdb said:


> No, you wont loose anything at all by only just using 5.1 on a 7.1 ch receiver. There are many movies now that have 7.1 channels of audio (bluray only) but if your only using 5.1 channels everything will be in those 5.1 channels.
> the Onkyo 609 is way more powerful than the Sony, Its rated at 770watts. The Sony you have now at best will only do 400watts
> HDMI is a must now a days as any sort of analog video signal is being phased out to prevent copying and to standardize. And to receive the uncompressed audio formats 1080p or 3D you must use HDMI.


Thanks. This has been informative especially being that I have not upgraded my receiver in several years. So the 609 would be the most bang for the buck, eh? I didn't see any when I searched eBay earlier. What should one of these run me if I bought the head unit only?


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## tonyvdb (Sep 5, 2007)

Go here, its the best price you will find.


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