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No power on

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发表于 2019-7-5 13:51:17 | 显示全部楼层 |阅读模式
MBX-270 motherboard
Question: No electricity
Cold test found no short circuit, all mosfets are no problem
The inserted adapter finds that there is no voltage on the CLR and does not activate the first mosfet. It is checked as usual, because both mosfets are NPN. If the drive voltage does not get it, it needs high voltage to drive mosfet. The requirement for checking ic is BQ24725.
The voltage is: pin number 20_19.6v, 16_6.2v, 04_1.3v, 06_2.7v (the problem of pin number 4 should be around 24 volts)
All requirements meet the high voltage of the pin number. 4 acdrv drive mosfet although the voltage did not come, even I have replaced the mosfet and charging chip but did not solve ... then, then...
I searched the chart and found that I wrote the mbx270 map, but it was completely different from what I did... I opened the BQ24725 datasheet and studied a lot of time and concluded that the ac test is responsible for acdrv and another thing most Sony The motherboard has a protection circuit but if the protection circuit is activated, there should be no 2.7 volts AC detection voltage at the pin number. 6
Finally I checked with DSO and added a time factor instead of finding the voltage of the pin number. 6 is continuous fluctuations I think it is responsible for acdrv and backtracking, found that there are 2 diodes connected vin and another connection protects me from removing the protection diode and the given supply... now the laptop is turned on
Now support and protection diodes find all components are no problem, so put a diode to connect it to work the protection circuit


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发表于 2019-7-5 15:07:53 | 显示全部楼层
sorry. I'm don't know....{:mocs_9:}{:mocs_9:}

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发表于 2019-7-5 21:45:25 | 显示全部楼层
保护隔离的维修案例  且是英文版的

欢迎外国的朋友来论坛

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 楼主| 发表于 2019-7-9 12:53:58 | 显示全部楼层
Thank you sir

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