Gregory's Serverlooks like one or more MOSFETS in the big multiphase core regulator have failed in a short circuit. this is a very bad sign.
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33 comments
 @GeorgeRudolf strangely enough, the motherboard seems to work without the MOSFET. i'll still replace it though. @tubetime I used to live somewhere I didn't have the luxury of ordering from Mouser or DigiKey, so if my scrap pile didn't have it, it'd have to make-do on n-1 phases. But yeah. Make sure there's no gate drivers that could've gotten mangled...eh I'm preaching to the choir here :) @tubetime yeah normally it's source to drain, but I've seen gate driver/controller Ic failures before so thought it worth mentioning anyway.  @tubetime https://www.eevblog.com/forum/testgear/agilentkeysight-infiniium-mso9000-series-motherboard-repairupgrade/ Do these logic analyzers also run PCI-E over a SATA cable to the acquisition board? @tubetime did you need to swap the cpu, or did it survive the overvoltage? @tubetime seems a wonder it didn't die with that mosfet but maybe CPUs have features against mosfet latch up or the pmic detects it and shuts off thinking about the failure a bit more. here's the precise cause with a nice diagram. a high-side MOSFET failed in a short circuit, which would put 12V on the sensitive CPU core rail. however, the controller chip detected the overvoltage and turned on all the low side FETs (circled in green).  @tubetime ah so the pmic did protect the CPU, as expected, nice to see that even in this era such protections where already in placw, can't even begin to imagine the complicity of a pmic powering a modern Intel or AMD CPU.    @tubetime Have you considered upgrading the CPU? Looks like there are a few that are compatible with the socket and wouldn't increase the TDP. |
@tubetime I have, in the past, more than once, lazily used a 18650 cell to find the offending MOSFET, removed it, and kept on running the machine minus that phase.