Do failing LEDs flicker?

Probably lead-free soldering cracking up!

Fred-

Your c> Hello,

Is valid. LEDs do not flicker unless the applied voltage varies. They can be used to transmit information via light to another device at high frequency, or can remain on steadily without any variation in intensity for years.

Check the applied voltage with a meter, and check the connections. LED's are Solid State devices (Light Emitting Diode). I have never come across an intermittent one. They will fail open or shorted if subjected to conditions outside of normal, such as high temperature and voltage spikes. It's possibly a problem with the switch innards.

It's possible that you have a neon pilot light in that switch? They will flicker at end of useful life.

RKic

--
Robert Kennett

Are you sure it's an LED? Neon lamps flicker when they get old.

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Are you sure it isn't a neon tube? They do sometimes flicker when they are old.

Chris

are

I took the switch apart, and the "light" may in fact be a neon tube. It looks like a very small condom with a reservoir tip (sorry, but that's just what it looks like. I'm not sure if this is an LED, but the size is similar. Thanks again, Fred

If it flickers, it is a neon bulb.

Yup! NE-2 or similar.

Yes, it's a neon. The tip is where they sealed off the glass tube in a hot flame.

You can replace the neon bulb itself, but take note of the series resistor and size of the envelope (for example):

If you mismatch the resistor and the neon you'll either get too little light or shorten the lifetime.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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The

at

are

just

similar.

Thanks! Is my local electronics store likely to have a replacement? If so, will the resistor be matched up with the bulb when I buy it, or do I have to bring the original resistor in (I accidentally chopped it in half trying to bypass it -- don't ask). Thanks yet again!!!!! Fred

Hi...

Someone up there likes you! :)

Be very very thankful that your attempt to bypass it failed :)

Take care.

Ken

Go to your local electronics store, and ask for an NE-2. If the mains voltage is 120 VAC, ask for a 120 kohm 1/4 Watt resistor. If the mains is

220 VAC, ask for a 220 kohm 1/4 Watt resistor.

As for the resistor, it is not very critical. For 120 VAC, you can use anything from about 100 kohm to about 140 kohm. Double this value for 220 VAC operation. If you go higher with the resistor value, the lamp will be a little dimmer. If you go lower, the lamp will be a little brighter. If you go too low, its lifespan will be reduced.

You may have to buy these parts in a minimum quantity, unless the dealer has opened packages of these parts in stock. Most distributors have a minimum invoicing. You may have to shop around for a small quantity.

--

JANA _____

The

at

are

just

similar.

Thanks! Is my local electronics store likely to have a replacement? If so, will the resistor be matched up with the bulb when I buy it, or do I have to bring the original resistor in (I accidentally chopped it in half trying to bypass it -- don't ask). Thanks yet again!!!!! Fred

that depends on how good they are.

it may be easier (but not cheaper) to replace the whole switch with another neon illuminated switch.

OTOH you should be able to get the data on your replacement neon so you can pick the apropriate resistor for it and the voltage it's supplied from.

--

Bye.
   Jasen

a

has

Thanks all!!! I got it working. Fred

Also many 1/4W resistors are not rated for 240VAC use, but you might be able to put two in series to get sufficient voltage rating if you can't get the proper rating in a single resistor from your source of components.

Chris

I've seen it, but it's rare. Neon glow lamps often flicker as they get old though.

Fred, as it happens I noticed this same symptom on my pre-amp today. I was playing a CD and noticed the green power-on LED go off and then flicker dimly before coming on again. Since I built the pre-amp myself about 15 years back I am confident the soldering is ok and the resistors were all 1% Beyschlag metal film so I doubt it is due to this component. My guess, from the dim background flickering and then normal brightness, is that the LED is failing. I will let you know more when I have had a good look. And yes, I have seen LED's exhibit this symptom before.

LED

Unless the circuit board/connection was failing, LED's don't flicker, they just go to "silicon heaven".

Graham

Some LEDs of recent years have come from manufacturers shoddy enough to make some of their clunkers manage to flicker! (I have seen millions of LEDs, hundreds of different part numbers, with as far as I can tell all with semiconductor material excluding silicon for that matter!)

Meanwhile, I would still investigate other explanations, such as intermittent contact in a bad solder joint or the flickering lamp being an aged neon lamp! Illuminmated power switches to this day continue to mostly use neon lamps, and those often flicker when they have accumulated

10,000-30,000 operating hours where the AC line voltage is 120 or so (as opposed to 230 or so, where neon lamps with appropriate resistors can run much longer with merely fading before they start flickering).

- Don Klipstein ( snipped-for-privacy@misty.com)

Yes, they can flicker if the bond wire to the die is defective. When the LED heats up, the bond separates. It then cools down and makes contact again. Then it heats up and the bond separates. It then.....

Al