Cheap LED light interferes with TV

Catapult

Enlightened
Joined
Apr 17, 2003
Messages
383
Location
NYC
I just bought a cheap Muyan 9 LED light. I know I get what I pay for, but seeing Craig's and Doug's review; small, functional, cheap, comes with three free cheap AAAs, why not?

I thought 5mm LEDs were never strong enough to interfere with most electronics, but funny thing is, this light did.

The TV was on (the model is the last of the sony Trinitrons before they were finally discontinued) and as I placed the cells in and started to screw the tailcap, I noticed that the TV flickered. I continued to screw the tailcap and the TV flicked again. Each time I turned the tailcap, the TV would flicker. I decided to go crazy and twist it back and forth just to be sure, and yep, as long as the tailcap continued to be turned, the TV would flicker. Weird. This might have something to do with the following.

I was getting bored with the interference experiment so I went on to test the light. It seemed to light up only when it want to. I noticed in the reviews that the anodizing went all the way to the threads, thus not making good contact, which is true with this sample. I did not feel like scrubbing off the anodizing, so I left it and did something else. What I noticed about the switch was that I could not tell whether it was on or not, as most clickies have an "up" or "down" position that this one does not. Ten minutes later, I came back to try the light again. Whoa! It was hot! I immediately removed the tailcap to release the case containing the cells so they don't continue to cook. The cheap Panasonic AAAs were too hot to touch! Had I came back any later, they might have exploded.

Even if it is not producing light, it appears that a high amount of current would still run though it, enough to heat it up. Maybe that might also explain the TV interference, but whatever it was, crisis adverted. To the reject pile it goes.
 

kramer5150

Flashaholic
Joined
Sep 6, 2005
Messages
6,328
Location
Palo Alto, CA
I have had troubles with the two cheap 3xAAA torches I have owned. Both were in the $5 range. Both suffered intermittent connections. Neither caused the problems you describe though.

I would ohm out the 3xAAA carrier and the circuit in the light. make sure there are no shorts.

Is it possible the AAAs are defective?

RE: the TV flicker... Is your wall socket securely grounded to earth? Is it one of the older 2-prong power cords, without the ground lug? Is the television plugged into a wall socket controlled b a variable rheostat? make sure that is earth grounded. I can't imagine the interaction with the flashlight cap your body and earth ground causing the flicker via ESD. that seems really FAR fetched.

ESD/EMI/RFI bugs a tricky things. I have a denon home theater receiver and when I use a long extension cord and plug my headphonres into it, ESD builds up in the cord and I get shocked whenever I touch the plug.
 

Catapult

Enlightened
Joined
Apr 17, 2003
Messages
383
Location
NYC
Is it possible the AAAs are defective?.

Maybe, or maybe its the light itself, or both. The AAAs are still functional, although they smell a bit funky, like they are about to leak. I will check when I have some extra time.

RE: the TV flicker... Is your wall socket securely grounded to earth? Is it one of the older 2-prong power cords, without the ground lug? Is the television plugged into a wall socket controlled b a variable rheostat? make sure that is earth grounded. I can't imagine the interaction with the flashlight cap your body and earth ground causing the flicker via ESD. that seems really FAR fetched.

The wall socket is not grounded. The sockets are the even older non-polarized type. It's an old building. Probably have all kinds of wiring faults. Not much I can do about it.

There is a television, VCR, computer, speakers, etc. all confined in a small room. And when there are that many electronics, there will be miles of electrical cords. All those cords can act as a giant antenna, and could potentially pick up and amplify certain EMI or RFI. In this case, whatever that was going on in the light was strong enough to cause interference to be picked up.

ESD/EMI/RFI bugs a tricky things. I have a denon home theater receiver and when I use a long extension cord and plug my headphonres into it, ESD builds up in the cord and I get shocked whenever I touch the plug.

Yeah. Before the business relocated, at the previous location where I worked, some people were always getting violent static shocks by whatever or whoever they touched. The office were full of computers and servers, and several giant high voltage scanners. Perhaps the scanners were not properly grounded, and people would build up a charge as they walked across the thin carpeting. Funny thing is that only certain people were charged, including myself. May have something to do with what shoes or clothes are worn at the time. And sometimes, even having a drink of water would shock me as it contacts my mouth.
 
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