How does an amp channel short when nothing is hooked up to it?

[Nathan Raymond]

Just got my Denon AVR-X3700H back from warranty repairs at United Radio Consumer Electronics. Excerpt from the repair paperwork:

Please check speakers and wiring PRIOR to initial hookup.
Unit checked for customers complaint.
Repair covered under manufacturer's warranty.
Repaired shorted Height 2 Right channel.

I have only ever used it in a 5.1 speaker configuration. I never hooked up anything to the Height 2 Right channel. How in the world did the Height 2 Right channel short with nothing physically hooked up to it? Do I need to worry about this receiver failing in some other way because the true underlying cause of the fault wasn't fixed?

 

[Vini darko]

Just got my Denon AVR-X3700H back from warranty repairs at United Radio Consumer Electronics. Excerpt from the repair paperwork:



I have only ever used it in a 5.1 speaker configuration. I never hooked up anything to the Height 2 Right channel. How in the world did the Height 2 Right channel short with nothing physically hooked up to it? Do I need to worry about this receiver failing in some other way because the true underlying cause of the fault wasn't fixed?

Somtimes theres small manufacturing errors in components. This can lead to unanticipated failure.
They say its fixed so I'd belive them till proven otherwise.

 

[tomchr]

Well. It's not exactly clear what they mean by "shorted height 2 right channel". Are they saying that they believe the dead channel was killed by a short circuit? If so, I'm surprised they covered it under the warranty as that would probably fall in the "customer abused equipment" category. That leads me to believe that the cause was something else or that it's a known issue. If it's a known issue, I would think that they've worked out a permanent fix, so I wouldn't worry too much about it frying again.

How did you discover that the channel didn't work? Did the amp fail a self-test or something?

Tom

 

[Nathan Raymond]

How did you discover that the channel didn't work? Did the amp fail a self-test or something?

The kids were watching PBS at a low volume, when suddenly the receiver turned off, the power LED blinking red. I went up to it and it smelled of burning electronics. I removed all cables from the receiver, let it sit, plugged in just power and if I hit the power button it would briefly start up but within 1 second would turn itself off and the power LED would be blinking red again.

 

[tomchr]

Ah, OK. That sounds like a premature device failure. That does happen. Not often, but often enough. I wouldn't worry about it frying again.

I helped a friend fix a Sony amp that had suffered a similar fate. One of the output devices had shorted. I think it was also on an unused channel. The amp was about a year old. It fried on startup one day.

Tom

 

[Nathan Raymond]

Ah, OK. That sounds like a premature device failure. That does happen. Not often, but often enough. I wouldn't worry about it frying again.

I helped a friend fix a Sony amp that had suffered a similar fate. One of the output devices had shorted. I think it was also on an unused channel. The amp was about a year old. It fried on startup one day.

Tom

Ah ok. I guess this is a side-effect of the fact that unused channels aren't powered off in the AVR-X3700H?

 

[tomchr]

No. It's a premature device failure. Maybe the output device passed the manufacturer's test before it shipped but was either damaged during the installation or had a defect that didn't show during the test. The device might have failed sooner had you had a speaker hooked up.

Tom

 

[win]

I had the same thing happen to my Yamaha receiver years ago. Yamaha fixed it under warranty and it's been rocking my garage ever since. Love that thing.

 

[Weeb Labs]

One of your output transistors failed short. Simply a defective component.