13 Jul
2004
13 Jul
'04
8:05 p.m.
Hi All.
I'm in Japan and having a problem with a US monitor.
It won't turn on...no power light or power up noises
or anything.
So I measured voltage across neutral and ground and
there was 8VAC. So I got an electrician to wire up a
proper ground. There's still 1VAC across Neutral and
Ground.
So I have two theories:
1) The monitor is seeing the floating ground and not
liking it and refusing to turn on.
2) The monitor requires at least 110V (I'm getting
103V).
I'd hate to think this thing just died, so can anyone
confirm that a ground to neutral measurement should
yield 0V or some very negligible voltage?
Assuming the above two theories are bunk...any other
ideas?
Thanks for any help anyone can provide :(
Thanks!
Sellam
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14 Jul
14 Jul
1:21 a.m.
>>>> "Phab" == Phab E Oh
<phabi0(a)yahoo.com> writes:
Phab> Hi All. I'm in Japan and having a problem with a US
Phab> monitor. It won't turn on...no power light or power up noises
Phab> or anything.
Phab> So I measured voltage across neutral and ground and there was
Phab> 8VAC. So I got an electrician to wire up a proper ground.
Phab> There's still 1VAC across Neutral and Ground.
Shoddy wiring... not quite as shoddy now, but still pretty bad.
Phab> So I have two theories:
Phab> 1) The monitor is seeing the floating ground and not liking it
Phab> and refusing to turn on. 2) The monitor requires at least 110V
Phab> (I'm getting 103V).
Phab> I'd hate to think this thing just died, so can anyone confirm
Phab> that a ground to neutral measurement should yield 0V or some
Phab> very negligible voltage?
You can test that by wiring up a temporary adapter that connects
ground and neutral together. Do NOT use that for normal operation
because that would be dangerous.
I doubt that's the cause, though. The low voltage may be the reason.
But competent designers know that Japan's nominal AC voltage is lower
than the USA -- so the standard test spec for power supplies is 95 to
265 volts (low end of Japan to high end of UK).
If you can get your hands on a Variac that has the winding extending
beyond the input, you can boost the voltage to the monitor.
You might try a different location. It may be that you're suffering
from really bad wiring with unusually large voltage
drop.
Phab> Assuming the above two theories are bunk...any other ideas?
Your monitor may be busted... :-(
paul
7:04 a.m.
"Phab E. Oh" wrote:
I'm in Japan and having a problem with a US
monitor.
It won't turn on...no power light or power up noises
or anything.
So I measured voltage across neutral and ground and
there was 8VAC. So I got an electrician to wire up a
proper ground. There's still 1VAC across Neutral and
Ground.
So I have two theories:
1) The monitor is seeing the floating ground and not
liking it and refusing to turn on.
2) The monitor requires at least 110V (I'm getting
103V).
I'd hate to think this thing just died, so can anyone
confirm that a ground to neutral measurement should
yield 0V or some very negligible voltage?
If you are measuring between GND and neutral, a few volts measured is not surprising
(especially with a DMM with a high input impedance), resulting from inductive/capacitive
coupling between wires over the distance between your measurement point and where GND and
neutral are bonded in the building (assuming that Japan does a straight GND/neutral bond
as is done in North America).
The 103V supply voltage is far more suspicious, as it is quite low relative to 115V (you
don't say how old the monitor is, could it be that it predates power supplies with
'universal' supply voltage range?). Try finding a power adapter transformer to
boost the voltage. (Normal Japanese line voltage is lower than North America isn't
it?). Or if you are around electronics people, try to find a variac, as variacs typically
have some boost on the upper end of their range (for example, a variac fed with 120V will
typically boost to at least 130V, keeping in mind if the variac scale is presented in
volts, the scale accuracy will vary with the input voltage). (Or, being very careful not
to go to the low end, wire up the variac in reverse).
Or (if the monitor is older) there's always looking inside the monitor for jumpers, or
alternative primary taps on a power transformer, to select input voltages.
10:42 a.m.
Hi All.
I'm in Japan and having a problem with a US monitor.
It won't turn on...no power light or power up noises
or anything.
So I measured voltage across neutral and ground and
there was 8VAC. So I got an electrician to wire up a
proper ground. There's still 1VAC across Neutral and
Ground.
This should not be a problem. No device should ever assume that either
side of the mains is close to earth potential (because in some cases it
won't be). US wiring is uncovnentioal in that the neutral and earth are
connected at the house's fuse/breaker box, this is not the case in other
countries.
So I have two theories:
1) The monitor is seeing the floating ground and not
liking it and refusing to turn on.
I can see no reason why it would object!
2) The monitor requires at least 110V (I'm
getting
103V).
Possibly, but fairly unlikely. A PSU should be able to take +/-10% from
the nominal mains input. Which would mean it should take 115-11.5V
(103.5V). You'd be very unlucky for it to object to 103V.
I'd hate to think this thing just died, so can anyone
I assume you've checked the fuses (including the internal one in the PSU
area). Have you done any other internal tests?
My guess is that the startup resistor has gone open. It happens. Look for
a resistor (maybe 2 in series) of a few hundred k from the +ve side of
the maisn smoothing cap to some point in the choper circuit.
-tony
7467
days inactive
7467
days old
3 comments
4 participants
participants (4)
-
ard＠p850ug1.demon.co.uk -
hilpert＠cs.ubc.ca -
phabi0＠yahoo.com -
pkoning＠equallogic.com