Arduino shocks me on USB port

i found previous post here haven't been able solve own problem.

i built hyperion ambilight following guide on mediaportal forums found here.

the parts addressing 5v 8a led psu, ws2812b led strip , obviously, arduino.

i have never worked ac followed instructions how wire psu using guide on this page.

all went actually. leds working, got colors calibrated etc. life good!...until started put case. when touched arduino got mild shock usb port cover. thought @ first psu case since read if ground , neutral mixed may electrify case made mistake before , fried previous psu mixing up. got multi-meter , got no reading on psu case. touched psu case , no shock. thought maybe had been static discharge worried me more thinking might have fried arduino. went remove usb cable arduino , got shocked again. it's not large voltage, annoying contant. fact there concerns me not right , might ruin whole setup, particularly raspberry pi since connected arduino,  if don't figure out. 
i have simpler adalight led setup on pc uses arduino , checked 1 , fine. i'm including crude sketch of connections see if can tell me may have done wrong. know might bad psu mentioned in other post had similar issue want make sure might case before buying find out had nothing issue.
i complete amateur electronics in particular case don't know aside double checking connections. 

if getting shock anywhere on case, including usb plug cover, have sort of live connection ac line.

this extremely dangerous situation, guaranteed fry electronics, if doesn't kill or family member first.

throw psu recycling  bin , use quality, safety inspected, case grounded, 3 wire ac plug power supply project.

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