[Rack] problems in Susan the Rack: two machines died

jim jim at well.com
Sat Feb 27 12:00:24 PST 2010



   i had two 1U computers running in Susan the Rack. 
   yesterday (Friday 20100226) i discovered neither 
was working--neither would power up. 
   i discovered that both were plugged into the back 
of the UPS, where i'd left them not plugged in (to 
save power: 100 to 200 Watts 24/7 as opposed to a 
few hours each week when the linux sysadm study group 
meets). also, there's a new dent in the back of one 
of the boxes. 
   i removed one, took it apart, and dissected the 
power supply. line power appears at the plug at the 
back and on the connections on the PC board, but 
power is not distributed throughout the sub-systems, 
all pins in the molex connectors were dead. 
   i'm guessing this is the state of the other 1U, 
as both show the same symptoms. 
   the coincidence is suspicious: two machines both 
working and then both not working and with the same 
symptoms. there are two commonalities. some person 
has definitely dicked with the two boxes, if only 
to power them up, perhaps to have moved them or 
dropped them.... also, both were plugged into the 
back of the UPS. Both seem to have suffered the same 
catastrophe. 
   Did someone drop both? Did someone make some 
connection that presented overvoltage (or a hot 
ground...)? Did the UPS hiccup or otherwise 
misbehave and fry some component in each of the 
two power supplies? 

   if you have an idea as to what happened to both 
of my 1U boxes, please let me know: i'm unemployed, 
have little money, have spent a lot more money than 
i'd planned on noisebridge stuff, and now have to 
spend more money to repair these boxes. knowing 
what happened will help me diagnose and defend 
against future such calamity and possibly spare me 
some future expenses. 
   i note also that the wiring in the back of the 
rack is a mess, worse than most i've seen in the 
backs of racks. i will likely try to dress the 
wires somehow. i ask that anyone working on the 
rack remember to be excellent to others working on 
the rack and adhere to standard practices in wiring 
and fastening and power and bandwidth 
infrastructures. 
jim 
415 823 4590 my cellphone, call anytime 




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