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Denon AVR-3105 Unit tries to come on but after a few seconds power LED flashes red. (Unit shuts down) I found transistors Q1015L and Q1035L in the output circuit shorted. However, replacing these transistors had no effect on the symptom. The unit still shuts down. I don't have any other transistors in the output circuit shorted. Where should I go next?

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Look for open resistors in the same area. Also, if the transistors that you replaced are the output transistors, you should replace their compliments as well. I don't have the service manual with me at the moment, so I'm juist giving you generalities. If you can, lift the center pin of the output transistors and measure (and post) the voltage readings on each of three pads for each transistor. That should give me enough info to guide you further.

Thanks,
Dan

Posted on Oct 07, 2008

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(Probably too late to help you, but I'll post so others can see)
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I have found that they have one of 3 possible problems and they all require that the reciever be taken apart and fixed at component level. No way to tell what your problem is until it gets put on a bench and troubleshot.

Problem 1. This is the most common problem. One of the front channels shorts out. On the big heat sink the front channels are at each end. It is the front left channel (close to the display) This requires that the output transistors be replaced as well as some driver transistors and some resistors and a capacitor. Lots of work for a blown channel. Denon has put out a bullitin to upgrade the bias transistor and change a couple of resistors to help compensate for this failure. That channel overheats more than any other channel.

Problem 2. There is a resistor that is right next to the preamp board that opens up. It is a 10 ohm 1 watt resistor and when it opens, it causes the unit to go into protect.

Problem 3. The +12 volt regulator fails. It is in the power supply area on a smal heat sink right next to the -12 volt regulator. Generic part number is KIA7812 It also causes the unit to go into protect.

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