nashou
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Post by nashou on Mar 5, 2014 20:00:43 GMT -5
Those are protection transistor for thermal protection. There is a resistor across emitter and base so you may be reading that. I do not see where they would put B+ on the outputs. Also unlikely they would all blow out. Since the same DC is on all lines it has to be something common with every channel. Can you DC test all pins on CP404 to see if it is more then 1 protect line being turned on? Sure. I did that before but now all parts are back in and seem ok. DC DET 4 is 1.277 DC DET 3 is 1.523 ASO DET is 0 RADI Thermal is .255 TR Thermal is .257 |
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nashou
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Post by nashou on Mar 5, 2014 20:04:06 GMT -5
Just to add I have no heat sink on amp.
And is it ok I am using the chassis for GND when testing volatages?
Nashou
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Post by mastertech on Mar 5, 2014 20:33:25 GMT -5
You should be using highgnd for your neg probe. CP403, pins 7,8,9.
Recheck all your reading!
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nashou
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Post by nashou on Mar 5, 2014 20:48:57 GMT -5
You should be using highgnd for your neg probe. CP403, pins 7,8,9. Recheck all your reading! Same results on all readings The Signal lines and the Protection Lines. Nashou |
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Post by mastertech on Mar 5, 2014 21:27:18 GMT -5
On those pins of CP402, is there 1 that has a little higher voltage then the rest?
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nashou
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Post by nashou on Mar 5, 2014 21:47:53 GMT -5
they are all 54.6 the last one is 54.5 that is the white one.
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Post by mastertech on Mar 5, 2014 22:19:00 GMT -5
Well I guess you are just going to have to start pulling parts till you find it.Since the original problem channel was the FL then we will concentrate on it. When you pull some parts only worry about testing pin 1 of CP402. Of course I suspect once the DC disappears at that pin it probably will at the others also.
I want you to just pull a couple parts at a time and then test so we know just where the DC is coming from. Because the part you pull that takes away the DC may not be the bad part but would be the circuit to trace to find it. So here we go and I'm gone for tonight.
Remove:
R415 and R439 and test for DC.
If still there:
Q404 and Q410 and test.
If still there:
D403 and D404 and test.
If still:
R419 and R416
If still:
R417 and Q403
If still:
R429 and R434
I'm pretty sure by now you lost the DC on pin 1 of CP402 and hopefully the other pins also. Let me know and I'll check back tomorrow.
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Post by mastertech on Mar 5, 2014 22:20:13 GMT -5
they are all 54.6 the last one is 54.5 that is the white one. Just to verify, there are only 5 pins on this connector, correct? |
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nashou
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Post by nashou on Mar 5, 2014 22:27:17 GMT -5
they are all 54.6 the last one is 54.5 that is the white one. Just to verify, there are only 5 pins on this connector, correct? yes the connector with the Signal's for the channels. 5 wires. I'll work on it tomorow. I do hate how delicate these boards are , traces are easily lifted at the through holes. Nashou |
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nashou
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Post by nashou on Mar 6, 2014 17:37:58 GMT -5
Ok Mac, we are on to something.
Remove the first two resistors and DC went down to 29.xx on all channels.
Onto the next parts unless I should wait for your response?
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Post by mastertech on Mar 6, 2014 18:10:59 GMT -5
Continue.
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nashou
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Post by nashou on Mar 6, 2014 18:15:09 GMT -5
Removed 404 still DC
Onto 410
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nashou
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Post by nashou on Mar 6, 2014 18:21:37 GMT -5
Still DC but now its bouncing around from 26.xx to 28.xx etc.
Nashou
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nashou
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Post by nashou on Mar 6, 2014 18:48:37 GMT -5
Ok DC went down to 1.5 to 1.7 volts.
Still wont stay on. Decided to test DET points and then Smoke and flame from R 483 !1 it took out Q 416 and 422. I did not test DC after that!!
Crap!!! I have more so... but CRAP!!
And I lost one of the diodes somewhere!! Crap!!!
Nashou
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Post by mastertech on Mar 6, 2014 19:08:15 GMT -5
Remove Q416, Q422,R483,R458,D409 and D410 and retest.
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