Gregory's Serverwell, looks like it is going overvoltage and shutting down.
|
49 comments
 it's on the back of one of the boards! it's a M51995AFP chip. time to do some reading. and maybe Lambda has a service manual or schematic. maybe. well, i've reverse engineered the dang thing. there are a bunch of component values missing but you can check it out here: https://github.com/schlae/sws600-12  @tubetime I'd like the illogical decision to inflict Microsoft Windows on these boxes analyzed. 🤷 🤔  there's a soft short on the 12V line going into the motherboard. this was preventing the big power supply from going power good. @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. @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.  |
huh, it's a bit simpler inside than what i expected. there's only these two circuit boards. a few large parts, but where is the controller?