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Post by mastertech on Dec 17, 2013 20:21:58 GMT -5
Well this could be our problem. Let me look over these schematics and see whats what. I have something else I also have to do so I may be a while.
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Post by crudeau on Dec 17, 2013 20:27:56 GMT -5
You got it
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Post by mastertech on Dec 17, 2013 20:29:58 GMT -5
On that CPU board see if you can locate connector CY124. It should be in the middle of the board. Use pin 5 for ground and pin 8 for positive. DMM on DC voltage. What do you get.
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Post by crudeau on Dec 17, 2013 20:41:56 GMT -5
I don't see that one. I have a pretty good view of all the connectors. What does it connect to?
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Post by mastertech on Dec 17, 2013 20:54:57 GMT -5
Circled.  |
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Post by crudeau on Dec 17, 2013 22:02:29 GMT -5
Got it 5.40
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Post by mastertech on Dec 17, 2013 22:16:59 GMT -5
Ok, back to CY272 on that CPU board. Again, pin 22 for gnd and test pin 27 this time, the last one. If you get +5v then test pin 25 again and see if it is still low. If no +5v on 27 try chassis gnd and try again.
Going off for tonight. I'll check in tomorrow.
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Post by crudeau on Dec 17, 2013 22:28:26 GMT -5
4.77 on 27 with 22 as ground
Still low on 25
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Post by crudeau on Dec 17, 2013 23:11:47 GMT -5
I just saw three voltage regulators on the back of the power supply. Mounted to the chassis as a heatsink. Did one of your tests verify the have the correct outputs?
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Post by crudeau on Dec 18, 2013 10:49:54 GMT -5
And those to transistors are heating up every time I turn it
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Post by crudeau on Dec 18, 2013 11:03:02 GMT -5
Been googling and saw this too...
check for offset on the amp outputs. if you have rail voltage on the output isolating coils, you have a shorted pair of output transistors. another common protection problem with Denons is bad power supply regulators. in some models, the +/-15V regulators had a habit of going south. if you find one of them bad, replace both. those are the most common problems. lesser common problems are a bad active filter transistor for the diff amp supply (looks like it's used as a regulator, but it's really an "amplified capacitor" or capacitance multiplier). this would cause 20-25V offset in all amp channels at the same time. or a bad main power transformer (the main clue on this one is no display when the unit turns on).
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Post by mastertech on Dec 18, 2013 12:37:16 GMT -5
Ok, I guess it's time for a brief run down on where we are at so you don't waste your time googling and getting misinformation where people don't end up getting their stuff fixed. Also, 1 of the main reason I joined this forum and try to put out correct information for others to see.
As far as whether there are any real amp problems we don't know for sure yet but we have disconnect the amp section from protection and still show the protection circuit being engaged. This means we have a problem in the protection circuit it self. So, although all your google reading on the amp section may be true, it has nothing to do with your problem. Which is why a specific approach is always required when troubleshooting and AVR.
We have narrowed it down to now know that you are missing the +5v power that operates the protection circuit. So we now have to find out why. And we are using a very specific approach for this. Other wise it is shot gun trouble shooting which very rarely works. Which is also why many electronics are deemed unrepairable even by professionals.
SO, we don't know anything about the amp section yet because it is not even being turned on. As far as any regulators, again, we don't know yet because not all of those are being turned on. As far as your 2 hot regulators, some regulators normally run hot. Sometimes if the complete circuit is not active they will run hot. So until we get this thing at least partially running we cannot address any other things.
Hope this help clear some things up.
But we are getting closer. I will post your next step shortly.
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Post by mastertech on Dec 18, 2013 12:44:08 GMT -5
Ok, first I want to see if we can use chassis for ground on these next tests. Set your DMM on diode test and put 1 probe in CY272, pin 22(where you have been using) and chassis ground, and see if it shows short (0.00)
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Post by crudeau on Dec 18, 2013 12:45:33 GMT -5
Yup. I don't disagree with your approach. I was just bored and googling. Thought I'd post anything that looks possible. Again I do appreciate all your help. At least the unit is finally clicking. Got something happening. I can't wait to see tgat lcd turn on
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Post by crudeau on Dec 18, 2013 12:54:57 GMT -5
No short on 22
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