Solved Denon receiver no power

dano_61

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Hello

I have a Denon 9.3 receiver , I hit a bare wire and there was a spark now the receiver will not turn on, no power

Did I fry the unit ?

Please help

Thank you
Dan
 
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Sure sounds like it. :(

Where and how did this "bare wire" hit the receiver?

How much voltage was in this 'bare wire"?

Was this voltage AC or DC?
 

dano_61

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Thanks for responding Spyware Dr , what happened was I hooked up the speakers but did not noticed one speaker wire was exposed , when I repositioned the receiver the bare wire hit the side of the receiver and there was a spark not sure about the voltage or AC/DC
 
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Hmmm, strange. Speaker wires carry whatever level of current comes out of the amplifier. A typical 100-watt amplifier powering an 8-ohm speaker would produce about 4 amps at 30 volts (A/C).

Does the receiver have an input fuse that maybe got blown? They are usually found near the A/C power cord going into the unit.
 

dano_61

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Here are the pictures of the fuses , i do not have a fuse puller but I am planning on buying one , here are photos of the fuses
 

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Gr3iz

Mark
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The fuses look OK. If you shorted an output (speaker) wire, it seems like it would have fried the HOT (high output transistor) in the final power stage. You're indicating that there is no power at all evident? As in no lights, etc.?
 

Gr3iz

Mark
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I wonder if it may have blown the power supply without blowing a fuse. Can you try to unplug it for a period of time, say :30-60 and see if maybe a protection circuit may have activated in the power supply that will clear itself in time?

If this doesn't do it, you may need to decide if you think it may be worth trying to have it repaired vs. replacing it. Unless you are familiar with analog circuit troubleshooting techniques, and have soldering abilities to replace any potential components (which may or may not be easily sourced), it is unlikely that you'd be able to repair it yourself. Sorry. Not what you wanted to hear, but ...
 

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Allan
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Do you have a fuse in a mains plug in Canada ?
Could a breaker in the mains circuit have been opened by the short ?

I thought speaker wires didn't carry any current if there is no (music) output playing, am I wrong ?
 

Gr3iz

Mark
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I thought speaker wires didn't carry any current if there is no (music) output playing, am I wrong ?
Allan, did you ever turn up the volume on a stereo when nothing was playing? You'd likely hear a hum that increases with the volume control.
 

dano_61

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Do you have a fuse in a mains plug in Canada ?
Could a breaker in the mains circuit have been opened by the short ?

I thought speaker wires didn't carry any current if there is no (music) output playing, am I wrong ?
Allan I never of mains plug , there is no power after I plugged it in after sitting unplugged for two days
 

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Allan
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Allan, did you ever turn up the volume on a stereo when nothing was playing? You'd likely hear a hum that increases with the volume control.
Yes but isn't that a small signal with the average being zero DC ?

The power amp circuits I'm familiar with either have a split rail supply (+ and -) giving 0 DC on average or an output capacitor which blocks any DC from appearing at the output.

Am I missing something here Mark ?
 

Gr3iz

Mark
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Allan I never of mains plug , there is no power after I plugged it in after sitting unplugged for two days
That's British for the main AC plug ... ;-)
 

Gr3iz

Mark
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The power amp circuits I'm familiar with either have a split rail supply (+ and -) giving 0 DC on average or an output capacitor which blocks any DC from appearing at the output.
I wonder if we're confusing power supplies with power amplifiers. The output of a power amp drives a speaker by deflecting the cone in and out using electromagnetism in a magnetic field. There could be significant voltage at any given point in time, depending on the mixture of frequencies being amplified at that moment.

1620445741169.png
This is a lot simpler than the amp I'm sure we're dealing with in the Denon, but as you can see, the cap (C2) is decoupling DC at the input side. The power transistors, Q1 & Q2 are driving the output to the speaker, one providing negative voltage and the other providing the positive voltage.

It's been almost 50 years since I learned about this stuff, and rarely used much of it since, so I could be misremembering some of it. Wouldn't be the first time ... ;-)
 

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