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Yamaha HTR5940 Receiver Shuts Down Randomly, [moved from General Audio]
post Feb 24 2013, 17:20
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I have a Yamaha HTR5940 receiver that has a strange issue.

It seems to shut down randomly every 1 or 2 days regardless of volume levels. I cannot replicate this behavior on demand as cranking the volume up doesn't cause shutdown.

It is running 2 sets of speakers concurrently one 6.1 on stereo (both A and B).

The timer function isn't on.

If there was a short wouldn't turning up the volume immediately trigger shutdown?

I will try disconnecting the power to reset the unit.
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post Feb 25 2013, 10:04
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My guess is that somethings' broken. wink.gif

You would have to analyse the electronics inside the amp itself. For instance the failure may be caused by a failing power converter that isn't giving the main chip or whatever chip is responsible for keeping the whole unit powered on enough volts which then causes it to behave erraticaly and go into derp mode. If the unit works after having it powered off for a while which acts like a reset on the chip, then that's a good hint.

No matter what the actual mechanism of failure is, it's very often a failing electrolytic capacitor. Have a quick look inside the unit and see if you can spot any leaking caps. Bad news is, that even if you've found the bad cap, its shorting could have damaged some other components, diodes for example. Although the circumstance that the amp is not in a permanent and terminal state of failure suggests that it's not that bad. But even worse news is, that capacitors don't do their job properly long before they actually blow or leak, resulting in, if they are part of a voltage converter, not letting that converter put out the correct voltage. Checking caps that aren't obviously blown and which are still soldered in requires specialized test gear which you probably don't have and which isn't not cheap either.

Here's what you can do to verify or dismiss my theory: download the schematics to all the main chips, start with the biggest one. Or you could try to get a copy of the "service manual" for your amp, that's probably the better idea. Then identify the chips supply voltage pin, and check with a volt meter if the voltage is within spec according to the manual.

If you can't do that kind of testing, you should ask someone who can. You'll have to pay for a repair eventually, but it shouldn't be that costly compared to the value of the amp.
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