HP 8000 MT - 2nd PSU for GTX660?

Mar 24, 2018
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Are there any dangers in running a GTX 660 off the 6-pin PCIe of a separate 550W Corsair PSU (shorting power_on and using switch before and after computer to turn on/off)?
(It is impossible to simply replace the 'active 330w' PSU inside the machine as it uses proprietary connectors for mono power.)