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There is a customer complaint: but there is no image. Thecustomer himself did the cleaning and maintenance of the motherboard. then hecollected the computer and there was no vision
Visually inspected the motherboard once. I didn't see anybroken resistance or a damaged line.
Took the motherboard out of the case. There was anisolated label on the back of the motherboard. Took it off. and I saw that anSMD capacitor belonging to the CPU VCC_GT line had fried. and it was shortcircuited. Removed the short circuit capacitor. I started the motherboardstill the same situation. fans freeze fast and no display. Said to myselfthat I need to examine it from the sky now. there was signal timing in theschematic of the motherboard. Measured everything in order with the method. Iknow and the timing on the motherboard. All VRM output on the motherboard wasintact. there was just no VCC_GT voltage. There was an abnormally low value on the CPU VCC_GT line. 0.002 ohms.this was so abnormal. Removed the DrMOS IC. there was still a short on theVCC_GT line
There was a high probability that the CPU was bad. Ordereda scrap motherboard on ebay. Motherboard belongs to dell machine. had liquidcontact. Measured the CPU line, there was no short circuit. I changed the CPUat risk.
Took remeasures and the CPU line VCC_GT was normal. the averagevalue is 0.023 ohms
Everything is perfectly normal. I changed the CPU. Iconnected it to the power source and started. Still no image and still no voltage VCC_GT
Let's think a little...  Why is there still no image? The current drawn from thepower supply is normal. Meanwhile I reprogrammed the BIOS and EC. I edited theBIOS on the official site. I'm pretty sure it's the BIOS.
I connected post card from EC Debug line. post code 63. this error code points to IntelHD graphics card The VCC_GT voltage should rise instantaneously at the firststart time. I need an oscilloscope to see this too. When I examine it with anoscilloscope, there is no reaction at the VCC_GT voltage.
DrMOS measurements VCC - 5V active VIN - 19V active DRON - 4.94V active PWM – 5V – this is not normal. When I look with an oscilloscope, this signal is a flat DC voltage. But normally at low voltage and Ishould see a PWM signal
I then measured the BOOT resistance. I saw that theresistance value is abnormal. normally 4.7ohm. But when I measure 1.2kohm.
BOOT (5pin) and PHASE (7pin) were shorted. I thought thecondenser is broken. The olctum condenser is out. It was not a short circuit.Then I removed the DrMOS IC. I've measured out and still pins 5-7 are shorted.This means that DrMOS is now corrupted. For this reason, the main VRM wassending a straight DC signal as it detected a short circuit.
Now I found the culprit NCP302045 is written on the schematic of the motherboard. But on the motherboard part code AEQ0 - AOZ5312UQI
Since I don't have this integrated in my hand, I replaced itwith Sic632 ( 55A )
All problems with motherboard are now solved 
Good day... 
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发表于 2023-5-13 03:10:17
会员330025
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