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Thread: I need help with my receiver please

  1. #1
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    I need help with my receiver please

    Howdy all,
    so I have a Yamaha HTR-5730 that I need some help with. I've repaired receivers and amplifiers before, output transistors, tubes, ac filter caps, etc. but when I opened this one I realized I had no idea what I was looking for or what to test for replacement. I'll throw in some pics at the bottom of this post but first I'll give some history on what's been going on with this thing.
    About two years ago, the left channel completely died, and not knowing how to fix this particular type of receiver, I just spliced my speakers into the right channel and left it.
    Then, about a year ago, the different inputs quit working one by one. VCR, DVD, 6-channel, AUX, all died one at a time until I was left with just the CD input and now that too is done.
    When the CD input finally died, the tuner quit working too (or maybe the whole amp circuit, maybe the tuner still works but it's just not coming out)
    Power turns on and stays on. The display still works. No humming noticed during it's life time. Just no sound now.
    Like I mentioned before, I'm fairly competent with electrical repair. I just need someone more experienced to point me in the right direction in this case. Thanks for your time. Here are the pics:
    Click image for larger version. 

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    If anyone needs more detail just ask. Thanks again!
    edit: Also, I did a visual inspection of the components and noticed no scorch marks or deformities. When I opened it up, it was very dusty inside. Maybe caused some overheating?
    Last edited by Icon_xof; 02-19-2014 at 06:41 PM.

  2. #2
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    yamaha

    well the big thing on the left is the power supply transformer. look for a blown fuse.
    most amplifiers now are directly coupled meaning no output transformer like Pioneer uses.
    if your output impedance doesn't match the final output transistor network, you could fry that stage.
    your inputs go through a pre-amp before being applied to the volume control and the outputs. usually on the center tap of an audio taper potentiometer
    the output stages are of a push-pull configuration meaning the output of one half stage is applied to the input of the other so they conduct on both sides of the waveform.
    the main output transistors are mounted on a large heat sink to dissipate heat generated.

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    Thanks for the reply
    I found the fuse by the transformer and it's not blown. It was by the small transformer that's situated toward the back from the large one. You can see it in the pic, white with a blue strip on it.
    I'll have to open my speaker cabinet and check the impedance on the speakers to see if it was mismatched. I didn't realize that could fry anything in the receiver.
    I didn't see any output transistors. I was looking for the large kind that have two leads and use the metal case as the collector lead. I'll open it up a little later and see if I can find any under the large aluminum heat-sink you can see that's situated toward the front.
    So I pretty much want to start tracing the input signal from the inputs to the volume pot and look for burnt components or circuit traces?

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    amplifier

    I hope you know, to troubleshoot an amplifier you'll need an audio generator and a one or two stage oscilloscope.
    a digital meter will help with voltages, but to trace a signal at a certain frequency you need a scope.

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    I've never tried to troubleshoot an amp with a tone generator before, but I have access to the equipment to do it. I have audio software on my PC so generating a constant tone would be no problem. Is there a specific frequency I should generate for this task?
    My dad has a scope I can use.
    So do I generate an input tone of a specific frequency and then look with the scope how far it goes before it disappears
    ? And then, whatever component the signal dies at would be culprit?
    Sorry for all the rookie questions. Your time and input in very much appreciated

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