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Post by tritron on Nov 22, 2014 9:54:14 GMT -5
I just gotten Denon AVR790 and it will not power on. There is no power no standby light it looks dead, the relay does not click when i press switch.
Where to start ? It seems that no power is going to standby transformer. Is the problem with large transformer it seems to plug in to stanby board.
Does anyonw have repair manual for the reciver.
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Post by mastertech on Nov 22, 2014 12:30:35 GMT -5
You would first need to locate the power supply board. On it there is a component that looks like a small transistor but with 2 legs. Its location id is (ic1704). Test it like a fuse and see what you get.
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Post by tritron on Nov 22, 2014 13:02:33 GMT -5
Well measure voltages and it shows 124v at small transformer. 0V at legs of relay. I measured one of legs and ground on board and it showed 2.5v
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Post by mastertech on Nov 22, 2014 13:24:41 GMT -5
Maybe you misunderstood what I said. Receiver not plugged in, locate ic1704 on power supply board, set DMM on diode scale, test across ic legs, should test as a short, like a fuse would.
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Post by tritron on Nov 22, 2014 13:49:41 GMT -5
The part you mentioned tested fine with velleman dvm850bl. I took the board out and showed short i ordered regulator from mouser
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Post by mastertech on Nov 22, 2014 14:30:17 GMT -5
Interesting. Why did you choose to do that?
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Post by tritron on Nov 22, 2014 14:54:09 GMT -5
There is 0 voltage on relay legs. I measured voltage around and I all see is 2.5V I read that lack of power for relay is the part mentioned by you and regulator.
I checked diodes and they seem to by fine. I jost ordered regulator from mouser so I can replace the one on board
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Post by mastertech on Nov 22, 2014 15:03:24 GMT -5
View this and tell me what you think.  |
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Post by tritron on Nov 22, 2014 15:24:25 GMT -5
Dont you think ic1703 regulator is bad. I checked diodes i guess cold joint could be a problem. I did not see any breaks between legs of relay and rest of circuit. Traced few lines they seem to be fine. I guess I will replace when my parts arrive from mouser, too bad the only local store for electronic parts closed down in denver, co
I saw couple of standby boards for 39$ on ebay.
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Post by mastertech on Nov 22, 2014 16:31:30 GMT -5
As you can see in the image below the 12v supply path does not go through the regulator. What you need to do is test for +12v at ic1704 first and then go from there. You "must" use pin 2 or 3 of CN1701 for your ground probe. Now this does not mean that maybe the regulator isn't bad since you may not have the +5v standby either. But throwing parts at something is not the way to go either. You need to test things to "verify" bad parts. You may have a short that is pulling down the 12v line which would also then in turn pull down the 5v line. It could be ic1703 shorted, or could be something else. I gather you are a beginner at this.  |
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Post by tritron on Nov 22, 2014 16:33:45 GMT -5
First time fixing receiver. I build tons of electronic kits before. I will test it and let you know.
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Post by tritron on Nov 22, 2014 17:09:49 GMT -5
I tested it and I only received 2.5v
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Post by mastertech on Nov 22, 2014 17:25:00 GMT -5
Is the harness still connected to CN1701? If yes then disconnect it and do your test again.
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Post by tritron on Nov 22, 2014 19:37:07 GMT -5
Ok unpluged tested at 11.55V
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Post by mastertech on Nov 22, 2014 20:15:20 GMT -5
Ok. On that connector (CN1701) leaving it disconnected, DMM on DC voltage, test between pins 2 and 4 and tell me what you get.
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