I live in the US and have an interesting problem with my home theater system that Google couldn't quite solve for me. My home theater setup is as follows (I can provide model numbers upon request, if necessary):

  • AT&T Uverse box
  • Sony A/V Receiver
  • Viewsonic Projector

The Receiver and uverse box are plugged in to the same surge protector and the uverse box is connected to the receiver via HDMI. The receiver is then connected to the projector via HDMI and the projector is plugged in to an outlet on the other side of the room.

Here's the problem. This does not happen 100% of the time, but often. When a light turns on or off, the A/C turns on or off, washer, dryer, fridge, etc. When any of these turn on of off, the projector goes to the screen showing it is searching for a different source and simultaneously the sound stops. If I just change the source on the projector the sound does not cut out because the sound is coming from the uverse box to the receiver.

So far this sounds like this question:Why would my TV turn off/on when connected to a surge suppressor?, but here's where things get interesting.

I had this problem in my apartment and got a new receiver(for other reasons) and I still had the same problem. Then, I moved to a new house and the problem remained. At the old place I had a Time Warner cable box and now I have uverse box. Literally the only thing that has stayed the same in this whole thing is the projector. That would indicate that the projector is the problem, which it very well may be, but I wanted to get some more insight before I went out to buy a new projector.

So the question is, does anyone know what is causing all this?

3 Answers 3


Something is sensitive to fluctuations in voltage. My first guess would be the receiver.

Instead of buying a new projector or receiver, buy a power conditioner. This will ensure that your cable box, receiver and projector all receive a constant voltage.


Modern electronics work on low DC voltage, whereas house wiring is relatively high AC voltage.

To work, these devices take the AC input voltage and use a bridge rectifier to convert it to DC voltage. That only makes it so that there is now a DC voltage that has a large AC voltage ripple. To reduce this ripple they use capacitors across the output of the rectifier. If they decide to skimp on the capacitors then the IC's can go into shutdown mode as the voltage dips too low for them to operate correctly.
( There are also other ways of getting DC from AC, but they are more expensive, and usually don't exhibit this problem anyway )

If it were my device, and it is no longer under warranty, I would add capacitors to the power supply of the projector.
Unfortunately since you had to ask this question to find the reason, its probably better if you don't do this as you may install them wrong. There may also not be physically enough room for more capacitors.

So you can go and either hook it up to a line conditioner, or to a full time uninterruptible power supply.
Its also possible that running a dedicated cable from the breaker box can help.

There is also a possibility that you may have a grounding issue. If it exhibits this behaviour when the AV equipment are plugged into the same outlet, then grounding won't be the problem.


Either the equipment should be replaced or some electrical repairs/upgrades may need to be made.

Electronics are designed to operate over a particular range of input voltages. Flipping switches or turning on and off loads cause changes in the supplied power line voltage. Small shifts are normal, but larger shifts can indicate issues that need repair.

Normally, the electronics should be able to handle normal fluctuations, but with age, they may become more sensitive, and need replacement or repair. As Brad Gilbert points out, some electronics are designed with too little power filtering, perhaps with too little inductance or capacitance in the filter networks. Additional capacitors could be added to help.

However, certain electrical faults can also cause the issues you're having (e.g. open neutral, high supply resistances, bad connections overheating circuit breakers). Firstly, I'd suggest verifying the "no-load" line voltage in the house. With the major appliances turned off, the line voltage should be between 110 and 125 AC Volts. Most houses have two feeds, so I'd suggest verifying on a few different outlets throughout the house that the voltage is in the acceptable range. Next, I'd suggest measuring the under-load voltages. Turn on a couple large appliances, and check that the voltage is still in the acceptable range. If not, then this can indicate that there is a problem with the electrical supply to your house or the wiring in the house.

Outlet voltages can be measured most safely by using an in-line outlet power meter (the most famous brand is Kill-A-Watt), but can also be measured using a standard voltmeter.

The problems can also be mitigated by using an "on-line" UPS or power conditioner. They will take the dirty power, and use it to generate clean power. However, I'd suggest that the condition of your house's electrical system should first be evaluated before purchasing any sort of power conditioners.

  • Actually new devices can also exhibit this behaviour if they skimp on input capacitors. Commented Aug 24, 2014 at 15:34

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