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#52850 06/09/05 07:20 PM
Joined: Feb 2002
Posts: 56
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drgnz23 Offline OP
Member
I ran into a problem at an office where the pc's dont want to turn on but the monitors work great . I checked the voltage at the outlets with a fluke meter and it showed me 130 volts. Is the voltage too high and how can i fix this problem?

#52851 06/09/05 07:56 PM
Joined: Oct 2004
Posts: 265
D
Member
130V is within the guaranteed voltage Edison supplies us here in SoCal (+/- 10% of 120V which is 132V). If it goes above that threshold Edison is required to do something, otherwise you probably wont get any help from your provider. They don't want to adjust it since it effects others on the same transformer.

You probably can get a buck-boost transformer, though I've never installed one for that purpose.

I doubt that the voltage is the sole source of the problem. All computers should handle the voltage range that the power companies are required to deliver.

I would continue to search, I'll bet you your problem has a different answer [Linked Image] Good luck with it.

Dave

#52852 06/09/05 08:20 PM
Joined: May 2003
Posts: 2,876
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e57 Offline
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Are the computers on a UPS? Some have power monitoring that may shut them down in this case.....

Anyway, I would first check voltage at the panel, you might be having other problems too, if the voltage there is lower.

And, has anyone tried them in a non-130v outlet, 'when did this problem start' would be my first question.


Mark Heller
"Well - I oughta....." -Jackie Gleason
#52853 06/09/05 10:10 PM
Joined: Jul 2004
Posts: 625
S
Member
As far as I know, most computers of recent vintage have wide-mouth power supplies that will take something like 90-260 or so volts. So 130 volts is solidly in the range. (I'll leave a caveat that there may still be some really cheap computers out there that don't have wide-mouth supplies.)

#52854 06/10/05 01:24 PM
Joined: Jul 2002
Posts: 717
M
Member
If you are in an office enviroment, your supply just possibly could come from a step down transformer which might have adjustable taps. If this is the case you should be able to adjust the voltage supplied to 120 volts.

#52855 06/10/05 02:27 PM
Joined: Feb 2002
Posts: 56
D
drgnz23 Offline OP
Member
Yeah im in so/cal. I figured 130v was still within the range . The computers are not on ups's yet but they to dont like the power. A buck boost is also a great idea if it was one outlet but its the whole room maybe the whole building .Not quite sure . Havent got to involed into the situation. Ill look into all your great answers.
Thank you

#52856 06/10/05 05:45 PM
Joined: Nov 2002
Posts: 790
W
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Computer power supplies have two ranges: about 90V to 130V and 180 to 260V. They usually have a slide switch hidden in back (near the power cord inlet) to select which range is to be used. Inside this switches the power supply rectifier from a doubler circuit to a bridge rectifier.

Monitor power supplies usually can accomodate the entire range from 90 to 260 without switches.

#52857 06/10/05 05:55 PM
Joined: Feb 2002
Posts: 56
D
drgnz23 Offline OP
Member
Yeah i saw that switch in the back . ill try that

#52858 06/11/05 03:03 PM
Joined: Oct 2004
Posts: 806
Member
The switch might cause even more problems as you'll now be giving the power supplies a serious undervoltage condition! Probably wouldn't release magic smoke, but....

Just for sake of discussion, did you check that the computer's receptacles are wired correctly, that the neutral isn't open or reading high (say about 10-15 volts or more) referenced to ground? Recepts don't have hot/neut reversed?

Any possibility of heavy harmonics on the neutral? (Lots of computers in use or electronic fl-lamp ballasts sharing the same panel/transformer.)

It might be worthwhile in this case to buy/rent a power quality analyzer to figure this one out.

Good luck!


Stupid should be painful.
#52859 06/11/05 05:31 PM
Joined: Nov 2002
Posts: 790
W
Member
It's possible, with computer power supplies, to switch them to the 220V setting and run them off of 208 or 230V. This gets them away from any "junk" on the neutral issues. In a Y system, the computer power supply on 208V will conduct at different times (of the 60Hz cycle waveform) than the other electronic loads in the building. In a sense the computer power supplies would see "clean" voltage peaks. If for example you have the computer across phase A and C, its supply will conduct on the voltage peaks it sees 30 degrees phase angle from the peaks of phase A or C as seen from the neutral. And 90 degrees from the peak of phase B.

If you convince the customer to do this, be sure to put tags on the IEC female end of the cords that announce that they provide 208V and not 125V, so someone doesn't blow up a load expecting 125V later on.


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