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Old 05-01-2019, 08:25 AM   #3
Johndill
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Join Date: Aug 2015
City & State: NSW
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Default Re: Alienware 18 LA-9332P 3V, 5V short

Quote:
Originally Posted by piernov View Post
It's not always safe to remove a buck controller and power on the board because then the gates of the high-side MOSFET are floating, and they could pass current, meaning sending 19V to the 3V or 5V rail. If you need to power on the board with the buck controller removed, either disconnect the PJP jumper, remove the output inductor or remove the high side MOSFET.

Ignore PL501, PL502, PL503 and PL504, it's normal to have low resistance to ground there with CPU inside the socket.

You have several places shorted to ground that should not be shorted together and are mostly unrelated. I'm not sure what happened but this doesn't look good.
It's especially concerning to have PQ201 shorted but for now ignore that circuit as the 3V/5V circuit must be fixed first.


You should try to isolate the shorts as much as possible, so remove QZ1 and QZ3 (which are probably dead anyway) and check which side is shorted for both.

Disconnect PJP100, PJP101 and PJP102 and check which sides are shorted too. If they cannot be disconnected, remove PL101 and PL102.

Also check for a short to ground on pin 3 and pin 13 of PU100.
I've replaced everything I removed except PL101 and PL102 as I removed them to isolate the short earlier.

QZ1 removed:
pins 1, 2, 3, 5, 6, 7, 8 shorted, pin 4 good.

QZ3 removed:
pins 1, 2, 3, 5, 6, 7, 8 shorted, pin 4 good.

PL101 already removed:
pin 1 short
pin 2 good

PL102 already removed:
pin 1 short
pin 2 short

PU100:
pin 3 good
pin 13 good
found pin 12 short

cap PC117 short to ground, short was gone when I removed PU100 earlier.

Last edited by Johndill; 05-01-2019 at 08:30 AM..
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