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# LED Bulb Repaired

By on September 16, 2021

I found few dead LED Bulbs in my Junk Box I have not tested because of busy schedule. Bulb’s domes Opened for visual inspection. All of them are of 7W.

Visually tested everything seems fine and there is no damaged /burnt sign found on any LED.

As usual first tested Voltages on driver Unit. It shows 92V DC without Load it means driver voltage is Ok and problem is with LED Circuit (Driver Voltages vary on different wattage of bulb).this voltage reduces to actual voltage when circuit is in working condition. How to find voltage of LED used on this bulb……………………

So for testing of led I took 9V battery and connected one 1.5K resistor on positive side of the battery and checked LED one by one. I found Bad LED which I marked with red dot.

Mostly in LED bulb led’s used are of 3v/6v/9V or 12V as per circuit design and as per wattage marked on the Bulb. In 2nd photograph you can see the numbers of Led used on each circuit are different 3 out of 4 bulbs are having identical LEDs and one is having 18 LEDs on it but all bulbs are of 7W.

As per standard circuit all Led’s on PCB are connected in series hence if one LED goes bad it will affect working of whole circuit. Before removing the LED I have to make one Bulb as a donor to use working Led’s. So I put a side one bulb which is having 18 Led’s on it because none of other bulb LED type is matches.

From rest of three I have to use one bulb as a donor because all of them having identical Led’s. Now here is the trick to find out voltage of led.

Connected the bulb on power now using one tweezer I “shorted that bad LED” when power is on while doing this whole bulb was light up perfectly. Now it is confirmed the problem is that bad led and it need to be replace. Same time I tested voltage on load. It gives 54V dc.

So divide 54VDc with 6 led it comes 9V of each LED. (This PCB is having 6 LED). If 7 led’s used divide 54VDc with 7 Led’s it comes 7.71V (Approx 8V) you have to consider nearby value on higher side i.e. 9V this confirms in this circuit all Led’s are of 9V. If you count for 18 led’s divide 54VDc with 18 Led’s it comes 3V each led voltage.

For desoldering SMD LED easiest way is to use gas lighter. (Don’t try to desolder LED using soldering iron you will damage the LED). I took one helping hand made out of old CFL Bulb casing. I grabbed the PCB and put PCB holder on edge of my table and with help of Lighter I heated up PCB from beneath the LED which I wanted to replace. After few seconds of heating I just try to move the SMD if solder is melted properly and when I pushed the SMD lightly it moves & I pulled up the SMD using tweezer. Same way for resoldering SMD back just heat up & when you see solder is melting just place the SMD on it  &  done. Be care full about polarity of LED.

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PCB Holder Helping Hand……………………

Made out of old bad CFL Bulb casing & one crocodile clip which I fixed on top using Araldite epoxy. For make it little heavier I filed the hollow casing using white cement paste.

After replacing LED on PCB I plugged the bulb on power and it light up perfectly.

This way I fixed two bulbs back to the life.

This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.

Note: You can check his previous repair articles on Multimeter That can’t be Repaired

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1. Barry Kratzer

September 16, 2021 at 9:04 pm

Great job. I didn't know you could fix these bulbs. But, how do you get the dome off of the bulb?

Thanks,

Barry

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• Yogesh Panchal

September 20, 2021 at 1:56 pm

Barry Kratzer,
These type of Domes are mostly pasted using glue or some Domes having just Locking edge groove.using clothe just hold the base of bulb ( Just for safety)and try to move the Dome clock wise or reverse, need little pressure or you can make little hole in between Dome and Base edge and just popup the dome you can try with flat screw driver also ( Do not cut with hacksaw or it will difficult to stick it back).

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2. Eric Rice

September 16, 2021 at 9:48 pm

Thanks! Will try this in the future, especially with outdoor versions.

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• Yogesh Panchal

September 20, 2021 at 1:57 pm

Eric Rice,

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3. Gilberto Galindo

September 16, 2021 at 10:03 pm

Hola
Ese truco de usar un encendedor para los componentes SMD es una novedad para mi. Gracias por compartirlo.

That tip about using a lighter to remove or solder a SMD is newly to me as an amateur, so thanks for share it.
Take care!!!

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• Yogesh Panchal

September 20, 2021 at 2:27 pm

Gilberto Galindo,

Using cigarette Lighter is the easiest way i found.you can try it on any SMD part Removing by giving heat underneath of the PCB even you can change the USB charging ports of Mobile also just you need to keep the eye on the component id your component is free to move just stop the lighter.
i have also made one tool to make hot plat type device using "Door stopper tower bolt" you may find it in my up coming article.

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4. Albert van Bemmelen

September 16, 2021 at 10:23 pm

The tip not to try to desolder LED using soldering iron is exactly what I experienced when I tried to desolder such a bad led previously. It just wouldn't come off because it was extremely strong soldered onto the pcb.
I also noticed that a defect LED 230VAC Light often works again by just connecting it to a higher HV voltage. After which it again gives perfect light as if it wasn't broken. Which is the same effect when a defect Tube Luminescence Lamp is fed by a HV source without using both its emitting electrodes, by only using one good electron emitting electrode filament (they normally are both each about 6V, but a defect TL tube fails if one of both emitting sides is defect).

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• Yogesh Panchal

September 20, 2021 at 2:32 pm

Albert,
Indeed now a days many types of mini Gas torches are available. every technician must have tool.

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5. Babu M S

September 16, 2021 at 10:23 pm

Your given good idea to remove smd led bulbs by using lighter.Thank you very for sharing.

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• Yogesh Panchal

September 20, 2021 at 2:33 pm

Babu M S

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6. Carlos Guilherme

September 16, 2021 at 11:14 pm

Thank for your idea about the "helping hand made out of old CFL Bulb casing". I really like it.

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• Yogesh Panchal

September 20, 2021 at 2:36 pm

Carlos Guilherme,
Some time we can fulfill our technical needs from surrounding waste material just need to know process of how to make Best out of waste.

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7. September 17, 2021 at 12:30 am

Very good, Yogesh. A great class about Led lamps maintenance. The idea of using CFL bulb casing as a helping hand is very good, but not applicable to all countries. Your proposal is adequate for bayonet-type bulbs, but several countries use E-27 type. In this case, your (excellent) idea is no applicable. Anyhow, a very good article. Thanks for sharing.

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• Yogesh Panchal

September 20, 2021 at 2:41 pm

Henrique J. G. Ulbrich

I am agree some innovation are not applicable to everywhere.it is just amatter to utilize your surrounding to fulfill your needs.
Thanks!for the comment.

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8. Robert Calk Jr.

September 17, 2021 at 6:29 am

Good job, Yogesh. Every LED bulb that I see nowadays I have to destroy to open it up. It would be nice if they were easier to get in to.

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• Yogesh Panchal

September 20, 2021 at 2:42 pm

Thank you! sir,

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9. Parasuraman S

September 17, 2021 at 8:20 am

Learnt new tricks and many thanks for sharing! The PCB holder itself is very unique invention! Hat's off!

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• Yogesh Panchal

September 20, 2021 at 2:50 pm

Thank you! Sir,

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10. A L PANDIT

September 17, 2021 at 3:34 pm

Nice repair. Saved two bulbs from e-waste load. These led bulbs uses 0.5watt or 1watt SMD leds. Leds are constant current dependent devices. For 0.5watt/3Volt & 1watt/6Volt smd led, the led driver is designed to deliver 150mA current and for 1watt/9Volt smd led, it is rated at 110mA. So while replacing smd led we have to consider this rating. I have replaced smd leds with
the help of domestic electric iron and also repaired led drivers of both ratings.

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• Yogesh Panchal

September 20, 2021 at 2:52 pm

A L PANDIT,
Good attempt!

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11. Anwar Y Shiekh

September 19, 2021 at 5:00 am

Wonderful work, although most people would not bother given how cheap these bulbs have become.

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12. Yogesh Panchal

September 20, 2021 at 2:55 pm

Anwar Y Shiekh
These all tricks are applicable when the material is not easy to reach us.

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13. Humberto

October 13, 2021 at 12:02 am

Good repair Yogesh. I did not know about the trick of the Gas Lighter.

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