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Top-level
 same symptoms as before. it just...stopped working, and when i push the power button, the fans bump a little bit but that is it. i checked the POL power supply that was causing problems last time, but the issue is that it is getting only 4.5V instead of 12V. 53 comments
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? 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 Have you considered upgrading the CPU? Looks like there are a few that are compatible with the socket and wouldn't increase the TDP.  |
Gregory's Server
umm, so it looks like this enormous 600 watt 12v power supply doesn't work.