Monitor shakes w/ UPS

I would look for an EM source bothering the monitor from the outside. For example, having electrical devices sitting too close to the face of the monitor. I have an electric pencil sharpener which, when activated, causes a terrible shake on the display screen - and it's sits about two feet from the monitor.

The UPS does nothing useful to 'clean' AC power. Worse, in battery backup mode, the typical plug-in UPS outputs power so 'dirty' as to be harmful to power strip protectors. UPS manufacturers don't like to mention this because any electrical protection useful on the power cord is already inside that computer and monitor's power supplies. In short, you have assumed features in both that power strip and in that UPS that even their manufacturer's don't claim to provide.

Joe,

We had jitter problems in our monitors when we set them on top of a power distribution box. That was back in the eighties, and people don't use those power distribution boxes anymore, as far as I know. (They had a "master" on/off switch, and switches for the system unit, monitor, printer, and a few additional units. They were designed to sit between the system unit, usually horizontal back then, and the monitor.)

But the 60 Hz radiation from the box was too much for the monitor to bear.

Any-ho, look for any electrical appliances near your monitor - flourescent light, power strip, even an incandescent lamp.

It "may be" your building wiring. However, if the wiring uses cable (hot and neutral in a common sheath) instead of separate wires at some distance from each other (that predates even me - called "post and ??" or something), it is unlikely to create much of a magnetic field very far from the wires. More likely it is something much closer to the monitor.

Here is a clue - if the wires to-and-from the appliance or circuit are close together, the magnetic fields cancel each other a very short distance from the wires. If the wires are separated by a distance, as apparently they were inside the aforementioned box, they will radiate a

-Howard

joe snipped-for-privacy@yahoo.com wrote:

it

connected

SmartUPS

UPS

is

my

FYI: The older system is called "knob and post"; used until the late

"knob and post" might be another term...

A short Google suggests that "knob and post" and "knob and tube" are both correct terms for the old wiring that ran separate wires for the hot and common. They were strung in space, in my experience, between small ceramic insulators - in the same fashion as distribution wiring on power poles, but on a smaller 110/220V scale. It is the relatively large spacing between the wires that could cause stray magnetic fields some distance from them.

The point about transformers is great. Transformers operate using magnetic fields to transfer energy from one circuit to another. If they were 100% efficient, no magnetic energy would escape. But they are not. Even the relatively far weaker earth's magnetic field influences the path of electrons in a CRT - luckly it is a static influence and so does not create flicker. An unshielded or poorly shielded transformer close to a CRT will wreak havock on the image. Note that wall-warts are usually transformers in a plastic box.

-Howard