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We have an electrical circuit with these loads (all on different outlets): 15W aquarium pump, 250W LCD television, 35W cable box, 13W GoogleTV box, and a 100W ceiling fan (plus an integrated 50W halogen bulb). I believe this is a standard 20A circuit. this is in Minnesota in North America, and at 110 VAC, we should easily be able to run up to 1600 watts (calculating for an inductive load, which is not the case).

All of these things have been running at the same time without any problems, for over 4 years - new construction.

However, for the past couple of weeks, the television's screen flickers off and on whenever I blip the ceiling fan's rotary dial - turn the fan's dial on and then off, and the screen goes dark for a second or two.

It doesn't appear to be a problem with the television itself (at least, none that the internet can help identify). All of these loads (but for the fan) are active for several hours a day.

I've tried disconnecting each of these devices in attempts to figure out what's causing this behavior. The only thing that seems to set this off is the 13W GoogleTV box. when this box is unplugged, the television won't flicker when the dial is blipped.

This doesn't make any sense at all. We should easily be able to run a peak load of 1600W, and with everything plugged in, we have somewhere in the region of 500W.

Is there anything else I should look for, or is it time to throw in the towel and call in an electrician? I can take care of reasonably DIY-able circuitry, wiring changes, etc.

ThreePhaseEel
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alt
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3 Answers3

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Replace Capacitors in LCD TV Power Supply

I would suspect that the problem is within the LCD TV. The power supplies inside LCD TVs and LCD monitors use cheap electrolytic capacitors that go bad and cause problems with the device. Your symptoms are representative of the TV power supply just starting to go bad. Small amounts of transient noise on the AC power line caused by switching other loads on and off, particularly the fan speed controller, gets into the TV power supply and causes a disturbance such that the various DC voltages inside are momentarily going unstable. When the TV was new the capacitors in the TV power supply were able to filter out the noise and power line disturbance but as they start to go bad the TV acts up.

It is highly likely that you will continue to see degradation in the performance of the TV over time. A common set of symptoms to look for include:

  1. The TV may become difficult to turn on wherein you have to press its ON button multiple times to get it to stay on.
  2. In the failure progression you may observe a point where when you go to turn on the TV it will blip on for 1 - 2 seconds and then go back off.
  3. Eventually it may get to the point that the TV will just simply fail to turn on at all.

I have personally experienced this problem with two of my own LCD monitors and got them back to perfect working order by replacing the power supply capacitors. In this case the monitors were about 3 years old. At my place of work I have been reclaiming failed monitors, ranging in age from 2 to 6 years, that were set for scrapping simply by replacing their power supply capacitors. So far I've reclaimed over a dozen monitors that are now keeping their owners happy as 2nd or 3rd monitors off their company issued laptops. Most recently a colleague came to me with his LCD TV with the problem that it was failing to turn on. I replaced all the electrolytic capacitors on his LCD TV power supply board and he reported over the Christmas break that his TV is now working perfectly.

Michael Karas
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  • michael karas, thank you. this looks like the most likely scenario. buying a decent branded television at a discount is probably not a good idea, even if one of the major local warehouse stores carries it :) – alt Feb 13 '13 at 21:23
  • This is very interesting. Do you have any general tips on how to replace a capacitor? Obviously every TV / monitor is probably different, but where do you start? – Hank May 20 '13 at 18:50
  • @HenryJackson - The best advice I can give you is twofold. Firstoff this is an endevor that requires some mechanical and electrical type skills. Specialized but readily avaiable tools are required. The second part is that there are numerous web sites that show videos and photos of how to go about replacing LCD monitor power supply capacitors. You will learn a lot more spending some time looking there than I can give you in a couple of sentences here. – Michael Karas May 20 '13 at 20:10
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Thank you very much for your replies. The process has certainly been enlightening (no pun intended).

The fan controller works OK - swapping it out with other rotary switches (and regular on/off switches) did nothing to change the behavior we observed.

Plugging in other loads to an outlet on the same circuit - a vacuum cleaner, none the less, among others - also demonstrated the same thing.

...which indicates that the problem is most likely with the television's capacitors. Well, we got a decent enough discount when we bought it a few years ago, and things start to die as soon as the warranty expires, I suppose... :)

In any case, thank you, all!

alt
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0

Swap Out Your Fan Speed Controller

Given your symptoms and some experience with similar "gremlins" I would first suspect your ceiling fan speed controller. Old-school and/or malfunctioning speed controllers inject piles of noise back onto the power line - you might even hear the noise if you have audio gear with high impedance inputs like a guitar amplifier. Most devices seem to deal with power line noise without event, but the odd device (usually powered by a switching power supply and controlled by an embedded processor) seems to have trouble.

The test is simple: Replace the suspect speed controller with a modern one, or a switch. If you can switch your fan on and off without side effects, you've probably found the culprit.

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alx9r
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  • alx9r, thank you! turns out this wasn't the issue at all... the house is just over 4yrs old, so i didn't expect these (generally reliable) items to fail already. – alt Feb 13 '13 at 21:22