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Question

Sony STR-DH520 help (technical)

Mar 5, 2016 1:29PM PST

I'm about to crack the cover and poke about but have never touched a receiver before. I'm posting to see if there is something I may have missed before doing this and also to be directed for where I should start. I have the service manual.

Here is the issue. The left and right main speakers are both outputting from the right channel and there is no output from the left channel. When running tone test all channels work fine except these two both test to the right channel.

What I have done so far is go through every menu item and set the left channel to the highest offset possible changed all speaker configuration modes from mono to 5/2.1 and then after wasting a few hours testing with individual speakers on all channels to isolate each output I have done a Complete Factory reset and retested to no avail.

I can understand if one channel (op amp circuit) cut out but to have both channels come out of the opposite side is truly baffling me.

Any help would be greatly appreciated.

Discussion is locked

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Answer
Quick. Grab this service manual.
Mar 5, 2016 4:59PM PST

As an electronics tech or engineer it's rare to see the full service manual on the web. Grab this now.

https://docs.sony.com/release/MDSM/989055901_sm.pdf

With that you can scope out the paths and decide what you want to replace. While I am an electronics designer, I don't repair such things when they can be had for 200 bucks. But you seem to be missing this manual so I'll post it here.

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Have manual
Mar 5, 2016 5:13PM PST

I have that manual. Yes I was surprised as well Sony is sharing it. AFA the if the cost in time to fix it is worth it well that would depend on your circumstances. Replacement would cost about 1/3 of my monthly income so I will try to repair first.

Now I haven't worked on a circuit board since 96 or so so if you can point out the circuit in the manual I'm looking for that would be helpful. I've forgotten far too much. Back then I would not have had to post at all for help. Sad

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That is beyond what I do on forums.
Mar 5, 2016 5:18PM PST

Try AVSFORUMS and see if any tech will answer. Here I may help to find the manual but repair courses are done in the classroom. So I think that's where it belongs due to liability and more. Each failure can be unique and the gear to work this is an oscilliscope, the usual solder gear and electronic circuit design. Not that you need to design a circuit but to work a repair bench you would read the schematics.

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K
Mar 5, 2016 5:23PM PST

Sure thanks alot, If I thought it was just one of the op amp circuits I wouldn't be seeking guidance but the fact both circuits are routed to one output I was hoping someone could point where that could be happening. I will try that forum. IIRC I use to get some good information from there years ago.

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There's a section of the class I talk about
Mar 5, 2016 9:28PM PST

I title the class section "abnormal circuit behavior." You have to know your circuit, the symptom and make theories why it does what it is doing then look at the signals to see if you can confirm it. This is pretty advanced troubleshooting which you can see folk had a hard enough time with looking at the schematic and seeing normal operation.

Take a failure and in your head think about breaking the circuit with opens, shorts, component failures takes a lot more understanding of the circuit as well as probing the board to confirm to get a new lead.

Hope that helps.

Post was last edited on March 5, 2016 9:35 PM PST

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The cost of a part will be more than...
Mar 6, 2016 9:44AM PST

...buying a used model in good condition (~$100 on amazon).

This is one case where it pays to simply replace vs attempt a repair (which is unlikely, given how they are built).

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I agree. An example of cost.
Mar 6, 2016 9:55AM PST

The oscilloscope on the benches run about 2 to 3 thousand dollars each. So for a one off repair like this, unless the failure is something easy to spot visually the cheap exit is another receiver. I see these for the price you mentioned.

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I would replace component not board so not really
Mar 6, 2016 10:54AM PST

True it would probably be 150 total but then I'm sure the same failure point would show up and I'd be in the same predicament. I tend to over engineer when I repair so as to not have to deal with it again. And If I do replace then I will certainly not replace with a receiver that failed 2 months after my paid for 2 year warranty.

If I was to replace it what would you guys recommend for something in the $200 range (total shipped). I run a HTPC so I need at least 5.1 surround, Phono, cassette and cd components only. Oh and the output has to have a hdmi for the TV (finally upgraded from a svid).

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I'm not sure you have worked with newer receivers very often
Mar 6, 2016 1:35PM PST

The notion of 'over-engineering' is not really applicable. You are essentially still trying to insert a triangle into a round hole Wink

What is required? Examine the costs/benefits involved then replace it as necessary vs repairing something quite 'unknown' to you, even with a used model. Throw the (arguably) tantrum-like logic of 'I won't replace it with the same model since it broke 2 mos past the warranty' aside. Truth be told, a higher priced receiver is just as capable of croaking like yours did. It's a huge roulette wheel with many variables, and a bit of luck since they are mass-produced. Replace, and move on.

Most of the Onkyo/Denon/Sony/etc. models in your price range should suffice for those particular needs/functionality.

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Yup
Mar 6, 2016 10:44AM PST

Yeah back in the 90's I used to do board level repair for Horton controls (GE contracted) and know what your saying. Which is exactly the reason I am here asking this question. I was hoping there was someone who is familiar with these specific circuits and could point me to a component. For instance I diagnosed that a 8080 controller on certain boards would not function while the same model/number and even batch would function. this led me to an investigation that ferreted out the fact that it was a specifically designed incorrect marking to obscure the circuit from being bypassed. In doing so I found the watchdog circuit and disabled it for my testing and repaired the entire backlog of boards that my predecessor had been piling up for years.

Which really is why I wanted to find someone who is experienced in these type circuits as I'm sure they would know what chip would cause the bleed through that is happening without my breaking out the oscilloscope.

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I had hoped
Mar 6, 2016 11:29AM PST

With me giving a brief mile high view of one of the lectures you would see that we can't diagnose such without having it on the bench, tracing it and making theories about the failure. This is quite expensive to do in shops today so you turn to swapping out a board rather than fixing the board.

I think you are asking me to tell you which chip or component to change or check. Sorry, but electronics troubleshooting on a forum is still a board change answer.

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So in summary, you are looking for...
Mar 6, 2016 1:36PM PST

...a technical 'shortcut' that does not exist. Sorry.

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Where
Mar 6, 2016 10:34AM PST

I couldn't find the correct subforum for repairs.

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I have yet to find one.
Mar 6, 2016 11:30AM PST

AVS Forum is pretty good but you seem to want a service tech or engineer to work with this remotely. That's new and so far, haven't seen that happen.

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There isn't one because...
Mar 6, 2016 1:38PM PST

...these devices are truly not engineered to be repaired, just replaced.

Given the relatively low prices as related to a percentage of average disposable income, one can quickly see why there's no strong repair market anymore.