Power conditioner / isolation transformer

[wigginjs]

I just purchased a couple of power conditioners by "OneAC" (model #MD1170 which I understand is equivalent to PCM750A). When I look inside basically all I see is a big switch, a HUGE transformer, and a small board with some poly caps on it connected to the receptacles. I measured the voltage coming out of my wall and it was ~122.5VAC. Then I measured the VDC and it swung between -0.3 and +0.3. Now when I measure the voltage THROUGH the conditioner I see ~126VAC and a swing between -0.1 and 0.1 VDC. I've got two identical units and they measure the same.

Questions:

1) Huh? I thought this was supposed to regulate the voltage?

2) Do these provide surge protection at all?

[Glen B]

The term "line conditioner" is loosely thrown about these days to mean anything ranging from a glorified power strip with a few filter caps to a true power conditioner that outputs a clean, stable 120V, regardless of how poor the quality of the input. All you have is an isolation transformer in a box and filter caps across the load. The 126V reading you're getting is the no-load figure which will drop under use. Most isolation transformers have a slight boost to compensate for output voltage drop when its loaded. Judging by the difference between the input and output voltages, yours has about a 3% boost which is typical. BTW, nice work on the home theater.

[wigginjs]

Glen:

Thanks for the response. Will this protect my equipment from lightening? What other benefits, if any, will my A/V equipment have from being connected to it?

[Glen B]

You need a separate device that provides surge protection ahead of the OneAc. A Brickwall surge protector is a good choice. I use carefully selected MOVs with my balanced isolation transformers for surge protection. Some people criticize MOVs, citing as a reason the fact that they wear out and lose their effectiveness. I have not had issues with them over the years. They are inexpensive and I just replace them periodically.

Of course no surge protection system can protect against a direct lightning strike. The best form of protection is to unplug your equipment during an electrical storm.

If you already have a good, clean household electrical supply, you may not notice any benefit from an isolation transformer or any of the other line filtration products. If you have a dirty electrical supply, an isolation transformer may reduce noise riding on the power line and give your system a lower noise floor. You may also see improvements in the picture quality of video displays.

http://www.brickwall.com/conditn.htm