Led lamp repair

[Gaber Mohamed Boraey]

Hello everyone

The article maybe appear as simple , but I am just curious to know

We all have led lamps at home these days, and it all stop lighting suddenly
I’ve tried to repair different ways, of course it’s cheap to buy a new one, but I just tried repair because I had many, and had the tools for repair,

But sadly, all the different ways I’ve used failed, or in other words, repaired the lamp but for few hours

I’ve tried jumper at place of dead led in the led circuit, also tried silicon doide at the place of dead led, also different resistors, didn’t calculate just tried 1k Ohm 1ohm

Asking experts here, is it really possible to repair led lamp, and last for more time , for ex. Few months?, or when led burn it’s the start of led life end?, and repair not good idea?

If repair possible, what the right way for repair except changing the burning led with new one, as I think hardly get smd leds my country

Attached photos for burned led in lamp

 

[stenzer]

Hi,

the LEDs usually are in series, so if one is faulty the other ones in series tends to stop to ligth up. The LEDs are light up by connstant current, so if you are replacing the defective LED by a LED which does not have the proper current rating (too low) I would assume the new one would fail quite fast.

How do the repaired light bulbs fail? Which LED have you used to replace the defective ones? Or what have you tried to repair the light bulb, the attached picture suggests you have replaced the LEDs.

BR

 

[Gaber Mohamed Boraey]

How do the repaired light bulbs fail? Which LED have you used to replace the defective ones? Or what have you tried to repair the light bulb, the attached picture suggests you have replaced the LEDs.

The attached picture just for example, not real experiments

In real experiment I’ve used doide instead of burned led, also tried resistor , it worked but for very short time

My question, if I don’t have the same led as the lamp, is there any way of repairing or what to add instead of the burned led?

 

[stenzer]

Hi,

the question is what has failed after the repair, an other component/LED or the LED substitution?

I would assume the resistor or the diode which has been used to replace the faulty LED, as they could not handle the current which is responsible to light up the LEDs.

BR

 

[Gaber Mohamed Boraey]

the question is what has failed after the repair, an other component/LED or the LED substitution?

Another led of the led series failed , if repair, another one fail and so on

 

[BradtheRad]

The tendency is to create extreme brightness by overdriving the led's. I imagine that's how a manufacturer impresses customers. And I imagine they use the cheapest flimsiest led's they can obtain in bulk. So it's no surprise if the lamps burn out prematurely. Then customers buy more lamps. It's standard business procedure.

I think the led's simply get too much current. It's indicated by your experience with various repairs. Can you find the adjustment that reduces current to the led's?

 

[dick_freebird]

The question is "-Why- did the LED fail?". The cause may lie elsewhere.
One LED was the weak link, but what pulled the chain to break it?

LED lamp active components are some if the most cost-compressed
ICs, and costs get cut by shaving reliability and ruggedness (or not
designing that in, in the first place), and using technology that runs
cheap in production but is barely suitable (so has to sell cheap, and
profit requires that it -be- cheap).

They know you're not going to save the receipt for that alleged 7-year
bulb that only lasts 2 if you're lucky and power surges never.

 

[Gaber Mohamed Boraey]

I think the led's simply get too much current. It's indicated by your experience with various repairs. Can you find the adjustment that reduces current to the led's?

The leds are driven by constant current led driver, you mean voltage change across the leds?, more voltage cause led to burn?

 

[BradtheRad]

The leds are driven by constant current led driver, you mean voltage change across the leds?, more voltage cause led to burn?

Correct. So by reducing voltage you also reduce current. The aim is to reduce power in each led, thus reducing stress.

However since it's a constant current driver, then it may not be easy to reduce current. As you say you tried a few inline resistors but that doesn't necessarily limit current.

Perhaps a parallel resistor? Or a bulb in parallel? To take some current from the led's. I can't be sure what ohm value is reasonable.

 

[Gaber Mohamed Boraey]

Yes, maybe that’s a good idea

Series resistor not take some of the current?

 

[KlausST]

Hi,

calculations
* using Ohm´s law and
* of power dissipation of a resistor
should be the most basic knowledge for anyone who is involved with electronics.

It seems you did not do any of these simple calculations, else you would know that 1k resistor it not suitable at all

Klaus

 

[betwixt]

Adding a series resistor probably wont help. The constant current driver will just increase its voltage (within it's limitations) to compensate and restore the same current as before. Shunting some current through a resistor in parallel will work but increase the load on the already stressed driver and increase the heat produced, probably counter productive overall.

The real fix is to find the component that monitors the LED current and change its value to set lower current.

When LED lamps fail like that, I tend not to repair them unless I have like-for-like parts. Unsoldering and replacing individual LEDs is almost impossible at home because of the metal substrate they are mounted on, however to salvage LEDs, a trick is to heat the back of the substrate on a gas flame (to spread the heat) and as soon as the solder starts to melt, hold it in pliers and tap it gently on to a safe surface, all the LEDs will fall off and apart from the faulty one, be reusable.

Brian.

 

[KlausST]

to heat the back of the substrate on a gas flame

Other options: heat gun, or iron (used for clothing), I even used a rather thick aluminum sheet (10mm) on a kitchen stove for SMD soldering.

Klaus

 

[Gaber Mohamed Boraey]

Adding a series resistor probably wont help. The constant current driver will just increase its voltage (within it's limitations) to compensate and restore the same current as before. Shunting some current through a resistor in parallel will work but increase the load on the already stressed driver and increase the heat produced, probably counter productive overall.

How add shunt resistor or pararell resistor on circuit like this?

--- Updated Dec 9, 2023 ---

Other options: heat gun, or iron (used for clothing), I even used a rather thick aluminum sheet (10mm) on a kitchen stove for SMD soldering.

I know how, but just hardly find same specifications of smd led, that’s why thinking of other solutions

 

[stenzer]

Hi,

if your light bulb is using the shown circuitry, than the other LEDs will fail for sure if the defective one has been replaced by an ordinary diode or resistor. Here, no constant current is used, instead a voltage of 16V is used. If you are replacing an whitish LED with an ordinary diode, will cause a higher voltage drop across the remaining LEDs and consequently a higher current through them

BR