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Discussion Starter · #1 ·
I posted this the other day on the thread specific to my receiver, but thought I'd add it here to see if anyone else had seen this or had an idea:


OK, I knew when I built the cabinet that it was more enclosed than it should be for any receiver. I have 2" clearance on top and 1" on either side of my Denon AVR789. It's open to the front and back. It worked fine for 6 months in that cabinet, but has started acting strangely, and I'm not sure if this is a heat problem or something else.


After using the AVR for a while, if I turn off the power and then try to turn it back on, the power does come on. The front display lights up and acts normally and responds to all commands from remote or panel buttons. But there is no sound and no picture. No source will result in any sound output from either speakers or headphone jack.


First I tried the system reset, but this made no difference. Then I left the power off for about 24 hours and when I powered it up it worked fine again. I left it on for several days and no problems. But when I turned it off and back on it no longer put out any sound.


This pattern has repeated several times over the past month. If I leave it off for some time it seems to "rest" enough to recover and then it will work again (one of these rest periods lasted almost two weeks before it would work again). Certainly after a day of rest there is no heat left around the unit, so I can't imagine why it will recover sometimes after one day, and sometimes won't work unless I leave it off for a week or more. And why once it works, it will continue working for days until I manually turn it off.


Amplifier? Processor? Any ideas?


I haven't tried to contact Denon, yet. I live in Africa, and have no authorized service centers nearby, and shipping it to one will be VERY expensive. Edit: after re-reading the warranty info, it seems that simply using the AVR outside the US voids the warranty. Bummer.


One other bit of information is that since power in my city is very unreliable, I am using the AVR on an ULTRA 2000VA UPS with auto voltage regulation.
 

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In your post in the 1909/789 thread, you didn't mention you had a "US" Denon 789 vice a EU model which would allow for the voltage variance in Uganda. That is very likely your problem as a US model is designed for 120v/60hz power whereas apparently in Uganda you get 240v/50hz power. If I'm reading the UPS spec page correctly, although it comes with AVR (automatic voltage regulation) and is able to handle an input voltage of either 120v or 240v, it does NOT convert from 240v to 120v, rather it just regulates the input voltage +/-5v to prevent any voltage surges from damaging the equipment connected to it. Get a voltage converter and that "might" solve your problem.
 

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I would think feeding 240v to a 120v-only receiver would kill it on the spot, rather than have it work normally for 6 months then start experiencing intermittent problems.


It sounds more like overheating to me. You do not have enough open space above the receiver for passive cooling. Active cooling with a fan blowing air through the space above the receiver could help, but it may already be too late. Heat shortens the life of most electronic devices. Six months of exposure to temperatures above the safe operating range may have damaged something, which is why you're now having problems even when the receiver is cool.


That said now, it could be power-supply related, as mentioned above. I'd get it connected to a nice, stable 120v source of some kind capable of sustained delivery of at least 1000w before trying to ship the thing off for repair. You may get lucky and find out it is just the incoming power.
 

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Discussion Starter · #4 ·
Before the UPS is a 220-to-110 voltage converter. So the UPS is getting 110v, and the Denon is getting regulated 110v, but really only 50 Hz.


It came back on again today, and I'm now running it with a couple fans keeping things cool - and they are keeping it pretty cool. I'm going to run it for a while and then see what happens when I power it down again, hoping that I can turn it back on without waiting. I'll update here later.
 

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The 50hz could be causing it to overheat as well vs the normal 60hz cycle, might want to add a fan or your voltage converter could also be causing the problem as memory serves me they are only for low draw applications, like a phone charger not for powering a large audio component.
 
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