[SOLVED] Fix a faulty flickering G9 led lamp

[firejim]

I recently bought some led lights 240V with cob and two of them start flickering with low yellow light. The first thing to check is the capacitors? would you advice me what to check for fixing the leds?
The specs for the led is like this :
**broken link removed**

Thanks in advance

 

[betwixt]

To be that small they probably use a simple capacitor dropper and bridge rectifier. Possibly the capacitor is faulty, replace it with one of the same value and at least the same voltage rating, higher voltage rating is better. I doubt they use switch mode supplies in a package that small.

Brian.

 

[firejim]

I could photo this I already open one led. The cap is 2.2uF 400V

 

[kam1787]

as betwixt said

can you remove the cap to test it? or measure the voltage across it?

 

[betwixt]

A photograph would be useful because there are two ways the capacitor could be connected. One is in series with the power where it works as a lossless resistor to limit the current, the other is after a bridge rectifier to lessen the ripple on the rectified voltage. If it's the second way, there will probably be another capacitor as well, probably an X2 rated one. I would guess the one you mentioned is the faulty one anyway, if it's electrolytic (has a + and - side) they have limited lifetimes and invariably are pushed well beyond their design limits in that kind of product. They are inexpensive and easy to buy.

Brian.

 

[firejim]

 

[betwixt]

Exactly as I suspected. The brown capacitor is used as the current limiter, the little black square is the bridge rectifier and the big black capacitor is the 2.2uF 400V electrolytic. I can't see clearly but there is probably one, maybe two small resistors in there too. The black 2.2uF capacitor is prime suspect, try changing it. Make sure you use one rated for 400V and 105 degrees C. Those lamps get hot and the normal 85C capcitors will cook quickly.

Brian.

 

[firejim]

3 small resistors are, I remove the capacitor and meter at 20μ and tells me 2.15 so it is right? is there any chance that could be faulty now? how to to measure it right to know if it is bad or good? thanks in advance!

 

[betwixt]

It could be any of the components, including the LED itself but based on likelyhood:

1. if the brown capacitor was shorted it would instantly burn out the LED (smoke & bang!)
2. if the brown capacitor was open circuit the LED would't light up at all
3. there will be a resistor across the brown capacitor - it is there to discharge the capacitor when turned off, it plays no part in the operation of the lamp
4. if there is a resistor in series withthe brown capacitor it is possible but unlikely it has increased in value
5. failure of the bridge rectifier would stop it working altogether
6. failure of the 2.2uF would give low brightness and flicker.

I would still say that capacitor would be prime suspect, especially as it has a limited lifespan and is probably being used above recommended temperature.

Brian.

 

[firejim]

thank you a lot you are a teacher! I have already order new capacitors and try to change it. I will practice till I found the problem

 

[betwixt]

Let us know how you get on. Be very careful if you try to power it up disassembled - there are dangerous non-isolated voltages inside!

Brian.

 

[firejim]

Ok i change it with a new one, at the beginning it started with no light and then suddenly it started to light but.. again low light and flickering

- - - Updated - - -

as I play with the switch i think its better but again low light..

- - - Updated - - -

I open it again and I saw it unstacked from one side, there is so small room in so when i close the cap it pushed more the capacitor .. I will try it again tomorrow

- - - Updated - - -

I think I will try to change the smd MB6S
I found this
http://www.ebay.co.uk/itm/10-PCS-MB6S-SMD-B6S-Bridge-Rectifier-0-5A-600V-AB-/181245673542?pt=UK_Computing_Other_Computing_Networking&hash=item2a33158046

 

[betwixt]

Try this instead: https://uk.farnell.com/jsp/search/b...k=gensearch&Ntt=mb6s&Ntx=mode+matchallpartial

Be very careful when buying components on Eb*y, especially from China. I'm sure the vast majority of Chinese companies and distributors are honest and reputable but the ones selling on that web site have a terrible reputation for selling rebranded, remarked and rejected components. Your mileage may vary but just be warned.

Brian.

 

[firejim]

also electr. capacitors?

 

[betwixt]

Yes, just about all components should be treated with suspicion. I apologize to the genuine suppliers on that web site but it has become a major outlet for fake parts. For peace of mind, always buy from companies like Farnell, RS Components, Rapid, Mouser, Eurotech and Digikey. Their parts have tracability right back to the manufacturer so you can be sure you get what you pay for.

Brian.

 

[firejim]

thanks again man, I am newbie, I want to learn so your advice is precious

 

[firejim]

ok, at last I change that too, so again is low light but not flickering anymore, any other to look forward?

 

[D.A.(Tony)Stewart]

I wonder what causes the flicker at low conduction angles. I reason that the flicker is faulty switching on either positive or negative cycles due differences in the triac quadrant characteristics and if the load current gets below the holding current, the triac will turn off. SO what determines the holding current? THe ESR value on the 2.2uF might limit the current at low phase angles being a low voltage. THe ESR on the LEDs are probably around 100 Ohms total, but the charging current current at trigger ought to be enough to latch the Triac. Datasheets are not very clear for this on Triacs. SO , my guess the lower ESR new electrolytic cap was the fix.