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I have a mains led lamp which was too bright

I bought a plug in dimmer switch hoping this would solve my problem

The lamp came on for a few seconds - it would flicker on lowest setting - then it went dead - any ideas what happened? 

I have opened it to have a look - there is  small circuit with one black round capacitor, one small glass fuse which appears ok, and 2 flatish capacitors?

Is it repairable guys? - its such a nice lamp and it would be shame to throw it away

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There are fundamental differences between dimmers used for conventional halogen and incandescent bulbs as against LED so if you use a plug-in dimmer that is designed for the former it will cause the LED to flicker and not function correctly the LED stands for Light emiting diode and to all intents and purposes is basically a resistor that is made from a material that glows when current is passed through it this is at a certain frequency and is controlled by a driver that monitors the frequency a conventional bulb is also a form of resistor but is set within certain current flow parameters that produces heat .

If you have used this type of dimmer it will not function on the leds and will probably destroy them.

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  • 2 weeks later...

Just seen this post, having been off-line for a couple of weeks.

LEDS that can be dimmed require a trailing edge dimmer technology, which is a little more expensive that the dimmers used for non-LED (which is leading edge dimming).

LEDS that are not suitable for any form of dimming certainly go AWOL as you get really odd current surges across the Diode junction which means they get too hot even though you are trying to dim them by reducing voltage.

Your lamp sounds a bit odd, as I would have expected at least one resistor as well as some capacitors.


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15 hours ago, steve2006 said:

Well the replacement is already here albeit another Chinese version (sorry if you are disappointed lol)

can't bring myself to throw the old one away though - its very nice quality and the clamp was stronger on this one than the new one

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Looks to me like the 4 pin chip (most likely that is the bridge rectifier, similar to an HD-04) has died from that brown smudge in the middle.
Difficult to tell as the pic is out of focus. I'm assuming that you tested if the fuse is still ok?
You could replace it with a similar one, if you can read the part number on it.

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Looking at that, cannot see why the bridge rectifier failed just because you were using a dimmer, but dimmable LED systems usually have slightly more sophisticated circuitry to allow external dimmers to work with them.

IMHO not so sure I would any form of dimmer with the new one that has arrived.

To think that when I was doing A-level electronics in 1976 that LEDs were rare and expensive, and we used to build LED matrices, and something like the picture, the LEDs alone would have cost about £15 (average weekly wage about £100 back then), and we used to use the valve technology for numbers as it was cheaper. 

How much we have progressed in over 40 years, thank heavens.  For dimming we probably just put a piece of cloth over our eyes!!!

LED Matrix.jpg

Valve Display.jpg

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Cheap (Triac based) dimmers use Width Modulation.
They switch off the power part way through each wave which results in voltage spikes that an incandescent bulb takes in it's stride, but those spikes fry unprotected electronics like rectifiers and transistors.
Dimmable LEDs have protection from those over-voltage spikes built in.

I love Nixie tubes but haven't worked with valves in over 3 decades.
The last valve I touched was in a Marshall 100W head, and it burned my fingers.🤣

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23 hours ago, BigBoomer said:

The last valve I touched was in a Marshall 100W head, and it burned my fingers.🤣

Used to knock up cheap valve amps as a teenager, gave myself a 600volt shock once, that hurt, but as I was using the trick of only use left hand to fiddle inside high voltage systems, heart was not touched. Also fiddled with a flash gun once, did not appreciate how ruddy painful the discharge on them is.

Now I just stick to fiddling with 240volts, much safer!!!

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