Hi all, really odd one here.
I have this mainboard from an E5540, unknown history but cosmetically in excellent condition. No signs of liquid damage, but slightly melted plastic at one of the HDD posts. Slightly peeled PCB surface at the battery connector, though it didn't appear to be burned.
It is shorted at +SDC_IN and other connected rails. I thought this would just be a usual case of injecting voltage into the shorted rail and seeing what heats up. Unfortunately, I cannot for the life of me find anything heating up when I do this. The power delivery area of the board does get slightly warm when +19V is injected into this shorted rail at PQ404 legs 5-8, but I cannot identify the source of the heat. PQ401 and PQ402 are not shorted at legs 2 or 3.
I'm going to lift off PL400 to figure out what side the short is on later, but I suspect it is somewhere on +SDC_IN as there are more components on this line. Anyone got any other tips? I'm really perplexed by this. All I can think is that it's a shorted ceramic cap I haven't yet identified (this is one of those nightmare boards where very little is screenprinted so I don't 100% know for sure where some of these caps are).
Attached pics, schematics are posted in this thread: https://www.badcaps.net/forum/showthread.php?t=79018
Thanks in advance
(Edit, forgot to add - my injection PSU shuts off totally if it's just applied to the DC connectors directly. I find this odd because it's fine when I directly target the rail)
I have this mainboard from an E5540, unknown history but cosmetically in excellent condition. No signs of liquid damage, but slightly melted plastic at one of the HDD posts. Slightly peeled PCB surface at the battery connector, though it didn't appear to be burned.
It is shorted at +SDC_IN and other connected rails. I thought this would just be a usual case of injecting voltage into the shorted rail and seeing what heats up. Unfortunately, I cannot for the life of me find anything heating up when I do this. The power delivery area of the board does get slightly warm when +19V is injected into this shorted rail at PQ404 legs 5-8, but I cannot identify the source of the heat. PQ401 and PQ402 are not shorted at legs 2 or 3.
I'm going to lift off PL400 to figure out what side the short is on later, but I suspect it is somewhere on +SDC_IN as there are more components on this line. Anyone got any other tips? I'm really perplexed by this. All I can think is that it's a shorted ceramic cap I haven't yet identified (this is one of those nightmare boards where very little is screenprinted so I don't 100% know for sure where some of these caps are).
Attached pics, schematics are posted in this thread: https://www.badcaps.net/forum/showthread.php?t=79018
Thanks in advance
(Edit, forgot to add - my injection PSU shuts off totally if it's just applied to the DC connectors directly. I find this odd because it's fine when I directly target the rail)
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