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Post by waltzwang on May 25, 2019 11:23:41 GMT -5
I bought a second-hand Onkyo nr-676e.But it doesnt work.when pluged,its stand/on light on,but no click,no display. i think its MPU is dead.but its cristal has 4MHZ ,its 3.3v is OK.how should I do next? I found before 141 of MPU the r7017 is open ,before 142 143 144 the r7017 is OK. can it cause mpu not work? 126 has 0v. 129, 130 have 0.65v. 138 has 0v.   |
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Post by waltzwang on May 25, 2019 11:45:19 GMT -5
push stand/on button,126,129,130 no change.143 drops from 3.3 to 0v.
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Post by waltzwang on May 29, 2019 19:01:23 GMT -5
pin 129 ,130 have 0.65v, pin 138 has ov. why cannot I turn on the reciever? Thanks for any advices.
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Post by mastertech on May 29, 2019 20:28:32 GMT -5
It is possible that 0.65v on 129 and 130 is enough to send it into protect.
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Post by waltzwang on May 29, 2019 23:02:44 GMT -5
Thanks for your reply. I cut off the r6705 r6704 d6704 . The mpu`s 129 130 still remain 0.65v.The reciever doesnt change. ![]()  |
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Post by waltzwang on May 29, 2019 23:18:25 GMT -5
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Post by tjmotter on May 30, 2019 9:11:23 GMT -5
Thanks for your reply. I cut off the r6705 r6704 d6704 . The mpu`s 129 130 still remain 0.65v.The reciever doesnt change. ![]() I don't believe that your MPU is the issue. The pins you reference are simply to drive the front display and each is fitted with a pull up resistor so all you are seeing on power up is that the CPU is asserting a ground to that line. This would be expected behavior when a pull-up resistor is involved. With respect to 129/130, 0.65V is fine. If there was a problem with the amplifier section, these would jump to a little over 1V causing the shutdown. Since they are not, I suspect the amp section is behaving normally.
The 3.3V (3.3VST) that drives the MPU is also tied to the 3.3S line that powers the HDMI ports. I would be looking at Q8401 and Q8300 as the source of the problem.
HTH Todd
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Post by mastertech on May 30, 2019 14:38:02 GMT -5
Thanks for your reply. I cut off the r6705 r6704 d6704 . The mpu`s 129 130 still remain 0.65v.The reciever doesnt change. ![]() I would not of suggested this. I would of removed D7002,D7003,R7025,R7026 and then retested at 129,130 |
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Post by tjmotter on May 30, 2019 19:07:46 GMT -5
Thanks for your reply. I cut off the r6705 r6704 d6704 . The mpu`s 129 130 still remain 0.65v.The reciever doesnt change. ![]() I would not of suggested this. I would of removed D7002,D7003,R7025,R7026 and then retested at 129,130 I agree 100%. Never cut a trace. It is MUCH easier to simply remove the suspect part and retest. |
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Post by waltzwang on Aug 10, 2019 9:30:05 GMT -5
Thanks for your reply. I cut off the r6705 r6704 d6704 . The mpu`s 129 130 still remain 0.65v.The reciever doesnt change. ![]() I don't believe that your MPU is the issue. The pins you reference are simply to drive the front display and each is fitted with a pull up resistor so all you are seeing on power up is that the CPU is asserting a ground to that line. This would be expected behavior when a pull-up resistor is involved. With respect to 129/130, 0.65V is fine. If there was a problem with the amplifier section, these would jump to a little over 1V causing the shutdown. Since they are not, I suspect the amp section is behaving normally.
The 3.3V (3.3VST) that drives the MPU is also tied to the 3.3S line that powers the HDMI ports. I would be looking at Q8401 and Q8300 as the source of the problem.
HTH Todd
I followed your advice. I found all the 1.1v on the HDMI board is shorted to the GND,and measured 0v. |
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Post by waltzwang on Aug 10, 2019 9:45:26 GMT -5
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Post by tibimakai on Aug 11, 2019 20:47:41 GMT -5
None of them is heating up?
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Post by waltzwang on Aug 12, 2019 2:12:18 GMT -5
Thanks. I touched the capacitors,and not found very high temperature . The capacotor seems well,but I am not sure. I welded off some of them. There is still a shortcut. I found Q8921 was damaged.but after it was welded off, the no.3 pin of PCB pad is still shortcuted to GND.there is nearly a 0 Ω. The the no.3 pin of Q8931 on PCB is also shortcuted to GND. After it was welded off, it Seems a good one. the no.3 pin of PCB pad is still shortcuted to GND.there is nearly a 30 Ω to GND. the vin(no.2 pin) of Q8921 and Q8931 has 12v, because of the shortcut ,they have no 1.0v and 1.1v. I doubt ![]() if the Q8401 and Q8300 are damaged. Many pins of them are linked to 1.0v and 1.1v. Then I checked the Q8401 and Q8300.I found the pins linked to 1.0v and 1.1v are all shortcuted to GND. Others are not. It seems the Q8401 and Q8300 are good. I dont know what to do next. |
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Post by tibimakai on Aug 12, 2019 10:06:06 GMT -5
I had issues like this in the past, and most of the time, one of the HDMI ICs were shorted. Most likely a lightning, or power surge killed it.
You may have to remove them, one by one and see, which one will lift the short.
None of the HDMI ICs are getting hot? Usually, when something is shorted, it is hot.
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Post by waltzwang on Aug 13, 2019 20:24:42 GMT -5
I found no extremly hot. I found a little warm on IC:Q8401 AND Q8300.
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