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Power supply diagnosis - should it give a "-5v" reading?

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#1 chugbug


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Posted 22 October 2014 - 09:53 AM

Hello all,


I'd like some help with diagnosing a power supply.  It's for a model ET1161 "e machine" circa 2008 +/- (at least that's the age I was told).  The PC belongs to my brother and he brought it over and ask me to check it out because it keeps rebooting and/or blue-screening.  In short, he said it was intermittent at first, then steadily got worse.


After I cleaned out all the dirt, I checked it with two different PSU testers (the type you just plug the PSU into).  One is an older PowMax, and the newer one is basically the same just with more LED's.  The PowMax and has a main RED light that lights up if it detects a an issue.  The RED light came on on that one, and neither testers show a "-5v" reading.


BUT when I look at the label on the PSU (a Liteon model #PS-5251-7) it doesn't list "-5v" with the rest of the  output volts.


So my question is this-- does the PC need or use the "-5v" or is it possible this PC didn't use it?


I'm going to get another PSU to test the machine, but I wanted an opinion on the -5v issue (both for now and if I run into it in the future).


Thanks for your assistance.




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#2 Scoop8


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Posted 23 October 2014 - 07:00 AM



The answer is "maybe", according to an ATX 24-Pin designation chart here . 


There's a notation about Pin 20 on the 24-Pin power connector.  The -5V output may be optional with the  ET1161 PC depending on the Mother Board's design.


I looked up some info about your Liteon PS-5251-7  Power Supply.  Here's an eBay link which indicate the P.S has the -5V output:


However, I see that this link doesn't indicate the -5V output available.


Based on your P.S. label which doesn't list a -5V output, I'd guess that this is accurate information.  The reason is that the PC's Mother Board doesn't require the -5V but to be sure, you may be able to look up the Mother Board's OEM specifications if there's a Mfgr's label on the Mother Board.


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