I recently moved into a town house and have noticed that my home theater, in particular the receiver seems to freak out and show only snow when I turn on and off fans and other electrical appliances. The snow lasts until I switch the input source on the receiver or power it off and on. This is despite having the receiver on a power conditioner.


  • Receiver - Denon AVR-1909
  • TV - Samsung HL61A750
  • Power Conditioner - APC AV H10
  • Cable Box
  • Xbox 360


  • Receiver -> TV - HDMI
  • Cable Box -> Receiver - Component
  • Xbox360 -> Receiver - HDMI

Do these fluctuations damage the receiver at all?

Is this a wiring issue in the house?

Also how could I track down the problem?

  • How severe is the snow? If you plug the receiver to a different circuit in the house can the issue be reproduced?
    – Mike B
    Nov 23, 2010 at 16:05
  • 1
    What type of receiver TV, cable, satellite, AM/FM?
    – Tester101
    Nov 23, 2010 at 16:27
  • Do you get the problem when using all source devices, or only one/some of them?
    – Tester101
    Nov 23, 2010 at 17:54
  • Do you have cable or satellite?
    – Tester101
    Nov 23, 2010 at 21:28
  • Do you own or rent? If you own, there are things you can do that might break a rental agreement. If you do own, do you know if local codes allow you to do your own electrical work?
    – Niall C.
    Nov 23, 2010 at 21:57

6 Answers 6


It could be a grounding problem -- electronic devices are often very sensitive to the quality of the ground line.

Invest in a receptacle tester and make sure that the receptacle with your home theater system is actually wired correctly. Do the same for all the other receptacles that cause the problem.

If you haven't already, map out which branch circuits supply power to the affected receptacles and fixtures. If they are on one circuit, can you move one or more of them to a different circuit? If they are on one phase (i.e. the breakers are all on one side of the service panel), could you move some of them to branch circuits on the other phase to see if the problem goes away?

Next, check that you actually have a ground from the service panel: look for a thick copper wire from the service panel that feeds to a grounding rod outside the house (my service panel is in my basement; the ground lead comes from the top of the panel and feeds through the rim joist to the ground rod).


How do you know that it's voltage fluctuations causing the problems and not RFI? Consider adding RF chokes to your setup to minimize that possiblity.


If you want to try looking for a voltage problem, you could get a simple multi-meter, stick the probes into the outlet and then watch it while someone else fiddles with other devices. You'll watch the AC voltage on the meter while someone else flips stuff on and off, and you might see a voltage drop.

The only way that voltage (especially through a power conditioner) should be a problem is if it's going VERY low. The power conditioner is nice, but it's not able to make up for insane voltage drops.

If you really believe that a voltage drop is the problem (as opposed to RF noise or something), get a real on-line UPS - Note the words 'on-line' there, that's important. What you want is a UPS that provides constant power in the face of brown-outs, black-outs, etc. The idea is to find one that's ALWAYS outputting from it's power conditioner and which has zero cut-over time in the event of power fail. Some cheaper UPS don't do that - instead they switch the source AFTER the power fails. That switch over can take hundreds of milliseconds. That's OK for some things, but for your purposes, it's not useful.

One other thing to check is whether the circuit your receiver is on is heavily loaded. If you are near the limit of the circuit (in other words, if you are close to tripping the breaker), then the breaker's activity when it's near tripping could be doing something funny to the voltages. If you suspect this, then you should try to get as much as possible off that circuit.

A kill-a-watt can be used to measure the load added by plug-in devices.

  • Would a voltage drop cause interference with the signal? or do you think the voltage drop causes the receiver to enter some strange half on half standby state?
    – Tester101
    Nov 23, 2010 at 21:26
  • A good UPS is a great solution and completely isolates load equipment from the 120vac utility source. Gotta love good Denon Equipment. Nov 28, 2010 at 14:59

If it is actually a voltage fluctuation, a simple multi-meter won't detect (without some finessing) since they typically measure RMS or average voltage. Here's what you do:

  1. Get an multi-meter, but make sure it has the capability to log min and max voltages, the Fluke 114 should do the trick
  2. Plug an extension cord into the outlet that is causing your appliances to malfunction and plug them all into the extension cord, leaving one outlet on the extension cord open for probing with the multi-meter (I say use an extension cord to make sure that you're measuring the same physical outlet from the wall, as I've seen in vary rare cases where one plug in a two receptacle outlet was run to a different circuit breaker and so the extension cord prevents you from measuring the wrong circuit)
  3. Place one of the multi-meter probes into either one of the slotted connectors of the open receptacle and place the other multi-meter probe into the other slotted connector.
  4. Turn on the multi-meter to AC voltage (should be a "~" symbol on the meter). You should now be measuring AC voltage and the meter should read about "110Vac"
  5. Hit the "Min/Max" button on the meter until the display says "Min"
  6. Do whatever you do to cause the equipment to malfunction and watch the meter. It should be logging the minimum AC Voltage it detects and displaying it. If your voltage drops significantly far below 110Vac, you know you've got a voltage dropout problem.

If the problem is a voltage fluctuation or even EMI (electro-magnetic interference), a good UPS should filter out the noise.


The fist step is trace the circuit to the breaker. Find out all outlets suppied by that breaker. After turning off the breaker LOTO Check each wire to make sure they are securly landed to each outlet (make sure the screw(s) are tight no discoloration to the wire coating) After verfying each outlet in the circuit you will know if you have 14 or 18 guage wiring and that will enable you to calculate the load you are putting on that circuit. So you can adjust, lower, the load on that circuit. If you use an UPS feed for your system it will help smooth out the current flow. It will also help protect it from a power surge.


Easier solution may be to buy a power conditioner and plug the av equipment into that. A "continuous coverage " UPS may accomplish the same thing. (Learned the value of these the hard way when equipment being used in a hotel kept resetting itself. Turned out the hotel's power dropped to 90V whenever someone used the copiers in the business center.)

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