Problem with ANTEC 500 w PS and an APC UPS unit

[Charlie Hoffpauir]

First, this is a home-built computer, with an Antec case and PS. The
3rd Antec case I've used for a homebuilt. The PS is a 500w Antec unit
that came with the case.

Problem description...

My UPS unit (APC 1250) failed to keep the computer running when we had
a severe power dip, so I concluded that the UPS was bad... (I had used
this same UPS with my previous computer, but since it seemed to be
working fine, I kept it when I built the new computer).

So I got a new APC 1500 (figuring bigger is better). Then another
power blip, and again the UPS failed to keep the computer on-line. So
I disconnected everything except the computer itself from the UPS unit
and ran a test by unplugging the UPS.... The UPS fired up but the
computer shut down.... but not immediately.

So I phoned APC support and they had me do a few more tests, including
unplugging the UPS with a normal resistive load connected (a lamp),
and the UPS worked fine, not a blink of the lamp. Another test with
the computer connected, and this time me watching the display on the
UPS, and the output voltage actually went crazy, varying quickly from
120 to less than 60 then immediately up to as high as 250 and back
down again, over and over until we unplugged the computer.... the
voltage then stabilized at 120.

The APC tech said that some power supplies needed a special UPS that
produced pure sine waves, rather than square waves.... and that they
were available from APC but were rather expensive. An alternative
would be to change the PS in the computer.


So... the questions are...

Has anyone else heard of this, or was the tech just blowing me off?

If this is plausable, what would be a good replacement PS?

Since I now seem to have 2 workable UPS units, would it "help" to have
both units connected, in series, so that power failure the unit that
the computer was connected to would get the square wave from the first
UPS, and perhaps filter it enough to keep the computer on-line?


The PS now in the case is labeled as Antec Earthwatts 500w max, model
EA 500D.

I'll appreciate any insight.

[Ron Hinds]

Post by Charlie Hoffpauir
First, this is a home-built computer, with an Antec case and PS. The
3rd Antec case I've used for a homebuilt. The PS is a 500w Antec unit
that came with the case.
Problem description...
My UPS unit (APC 1250) failed to keep the computer running when we had
a severe power dip, so I concluded that the UPS was bad... (I had used
this same UPS with my previous computer, but since it seemed to be
working fine, I kept it when I built the new computer).
So I got a new APC 1500 (figuring bigger is better). Then another
power blip, and again the UPS failed to keep the computer on-line. So
I disconnected everything except the computer itself from the UPS unit
and ran a test by unplugging the UPS.... The UPS fired up but the
computer shut down.... but not immediately.
So I phoned APC support and they had me do a few more tests, including
unplugging the UPS with a normal resistive load connected (a lamp),
and the UPS worked fine, not a blink of the lamp. Another test with
the computer connected, and this time me watching the display on the
UPS, and the output voltage actually went crazy, varying quickly from
120 to less than 60 then immediately up to as high as 250 and back
down again, over and over until we unplugged the computer.... the
voltage then stabilized at 120.
The APC tech said that some power supplies needed a special UPS that
produced pure sine waves, rather than square waves.... and that they
were available from APC but were rather expensive. An alternative
would be to change the PS in the computer.
So... the questions are...
Has anyone else heard of this, or was the tech just blowing me off?
If this is plausable, what would be a good replacement PS?
Since I now seem to have 2 workable UPS units, would it "help" to have
both units connected, in series, so that power failure the unit that
the computer was connected to would get the square wave from the first
UPS, and perhaps filter it enough to keep the computer on-line?
The PS now in the case is labeled as Antec Earthwatts 500w max, model
EA 500D.
I'll appreciate any insight.

You cannot connect UPS in series. This will damage the UPS units and could
in fact be a fire hazard.

What the tech told you about square waves is essentially correct, though
I've never heard of a power supply that required "pure" sine waves before -
at least not a PC power supply! I use Antec Earthwatts power supplies all
the time and have never run into this situation. At home I have an APC
BackUPS XS 1300 connected to a machine with an Antec Earthwatts 450 PS and
it has functioned flawlessly through several power outages. I have another
PC with an Antec Earthwatts 450 connected to a TrippLite and the same
result. At work I have a dozen computers, some with PS as high as Earthwatts
850, connected to APC and TrippLite UPS's and no issues there, either.
Perhaps the PS is defective?