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Post by mastertech on Jul 17, 2018 21:36:17 GMT -5
When that harness is disconnected it removes the protect signals and the unit should then function without going into protect. Since it is still going into protect we must find out why. This does not mean that there may also be a problem in the amp section but there is surely a problem with this harness disconnected. It would not be the first time I have seen a problem with the protect circuit and not an amp failure. But I have also seen problems in both sections. So we will have to see where this goes.  |
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Post by tibimakai on Jul 17, 2018 22:02:38 GMT -5
Every time, when I get an issue like this, I jump to the final transistors and very fast I can tell, if there is an issue there.
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Post by mastertech on Jul 18, 2018 8:51:13 GMT -5
Yea I wont disagree with you. The reason I chose the procedure we are on is because testing those finals can be difficult for a newbie and I also had him do an idle current test which he indicates was zero volts but that is providing he is doing that test correctly. But he is welcome to test those finals if he wants. |
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Post by brokendenon on Jul 18, 2018 10:09:40 GMT -5
Ok, on this same board I need you to find resistor R7618. DMM neg probe still on pin 6 of connector CN761 and then test both sides of resistor with pos probe and get me the 2 voltage readings. With the unit off, both sides are 3.27v When powering on, the left side(looking down at it) is 1.38v, and the right side is 3.27v. It takes a couple minutes for the left side to build back up to 3.27v after I shut it off...just like when checking at CN761. If I let the unit trip, both sides only build back up to 1v while the power is off. And goes back to the above numbers if I power it on. |
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Post by mastertech on Jul 18, 2018 10:21:43 GMT -5
The harness to cn761 is still disconnected, right?
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Post by brokendenon on Jul 18, 2018 10:25:40 GMT -5
No. Sorry! I will disconnect and retest...
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Post by brokendenon on Jul 18, 2018 10:30:42 GMT -5
With CN761 disconnected, both sides stay at 3.27v when powering on. If I let it trip, both sides go to .95v
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Post by mastertech on Jul 18, 2018 11:02:30 GMT -5
Ha, now it makes sense. And now we are going back to the amp board. Do you know how to test the final transistors tibi talked about?
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Post by brokendenon on Jul 18, 2018 11:12:50 GMT -5
What makes sense? lol
No, I don't.
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Post by mastertech on Jul 18, 2018 13:06:46 GMT -5
What makes sense? lol No, I don't. It makes sense because you should not have been getting the voltages you were getting when the harness was connected if that harness was disconnected. It was suppose to still be disconnected because I never said to reconnect it. To test the final output transistors set your DMM to diode scale and just test across each transistors 3 legs looking for a "shorted" reading, which would be near 0. There should not be any reading short. The finals are the large ones on the big heatsink. This is with the receiver unplugged from power. |
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Post by brokendenon on Jul 18, 2018 15:03:20 GMT -5
Gotcha! No shorts. Inconsistent opens, though... if that's important.(different legs on different ones are open) |
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Post by mastertech on Jul 18, 2018 18:35:34 GMT -5
I need you to check the dc voltage at the 2 red points in the image below. Use the gnd pin that you used before for the neg probe.  |
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Post by brokendenon on Jul 18, 2018 20:08:51 GMT -5
That looks like the underside of the main board, right? I have no idea how to access that!
And if I AM able to gain access to it, you wanting the voltage of it while trying to power it on, or what?
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Post by mastertech on Jul 18, 2018 20:21:39 GMT -5
Ok, scrap that test and do this one instead. These resistors should be on top. Just test dc voltage across the 2 resistors with neg probe on black circle and pos probe on red circle.  |
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Post by brokendenon on Jul 18, 2018 20:22:30 GMT -5
While trying to power it on, or what?
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