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iMac 5K 27" 820-00134 - Dead board due to USB?

Jay Khan

Registered member
Hi Friends,

I have an iMac, which customer says made a boom sound, and never turned on; board show no diagnostics lights. I inspected the board and it seems the 3rd USB port from left (looking at the back), had some issue, resulting in burn out of:

1. L4702 (dual filter) that carries the P and N channels of the USB.
2. L4701 - likely delivers PP5V_S4 to the USB.
3. U7700

Now, I am not sure if this could have caused the PCH to die as L4702 connects the USB to PCH. U7600 is not generating PP3V_S4 or PP5V_S5. PM_EN_REG_P5V_S4_R has 0.4v.

l4702-pch.pngl4702.png

I removed U7700 to see if it may help; but still no diagnostic lights. Any ideas?

Thank you!
 
all electrical circuits are linked together when a fire burns it will damage all related components, first you need to remove all burnt areas,
It's expensive but it's also an electronic device.
 
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