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Old 12-07-2012, 05:28 AM   #1
flexy
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Default Testing +5VSB on PSU to check whether PSU is defective

I am having comp troubles and with my limited resources here I try to troubleshoot whether the problem is PSU or motherboard related.
(Eg. mainboard doesn't start up right now)

I have a ca. 6 year old "Thermaltake Toughpower 750W"

When i jumper (paperclip "trick") the PSU PS_ON/GND (unplugged from board) then I can measure the rails, +3, +13, +15 etc. seem all be fine. PSU is also starting, fans spinning etc.

I even can put a 5V bulb on the +5V line and its lighting up.

Now to the +5VSB line (purple wire):

When I do this "bulb test" on the +5VSB line, the light does NOT light up. I am getting the same problem as if i would plug in the PSU to the mobo, board is not powering up etc. and I can hear a very soft 50hz "ticking" inside the PSU.

Questions:

If i put the 5V bulb to the normal +5 rail on the PSU and it lights up, but does NOT on the +5VSB rail, can I assume that the problem is with the PSU?

(Mind you that measuring the +5VSB rail with DMM otherwise tells me everything is allright, I measure 5V something on the DMM, however as mentioned I cannot drive the bulb from that voltage)
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Old 12-08-2012, 12:35 AM   #2
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Old 12-09-2012, 02:08 PM   #3
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Solved...it was a bulged cap on my Toughpower PSU. Shame on TT because this was NOT a "cheap" PSU. I am not the first where those "SamXon" caps bulge out and fail, lucky it did NOT fry my board. I recapped it and everything is fine again - PLUS i saved $$$ on a motherboard which I was already about to get, mistakenly thinking the fault would be with the board.
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Old 12-10-2012, 03:00 AM   #4
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Related Side-Note:

Don't depend on measuring rails with a DMM only - a DMM can very well show all the right voltages, doesn't mean the PSU is ok.

If you need to test a PSU you need a PSU load-tester!
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