Led lamp power source replacement - Page 1
Forum section: electronics / beginners

author: mircea L
author_rank: Newbie
timestamp: November 10, 2023, 05:09:07 pm
content: Hi,I am trying to replace the power source for a led lamp that failed.The power source has burned and took out some components ( including an IC ) that I cannot identify so I decided to try to replace the whole power sourceBut I am trying to figure out what should I look for , if there is such a thing , or should I build one.I have 2 of these lamps , one of them is working so I managed to do some measurements on that one ( but still cannot identify the components because the marking is quite bad and do not have a microscope )I did the following measurements:The voltage across + and - that goes into the led strips is 258V and the current that passes is 52mA so I am guessing that I should search for a power source that has constant current.I have attached a rough diagram of the led strips , there are 3 parallel rows of LED's , each one having 84LED's.In parallel with each of the leds there is a smd component which I cannot identify , it looks like a smd diode ( it seems to gave a bar at the end but it's to small to make out any marking)In the sketch I marked as a normal diode , I don't know if that is correct or what the purpose of that component is.I anyone could help me to identify what power source I can use to power and save this lamp it would be fantastic.V(AC)=258VI(AB)=52mAThanksMircea

author: mircea L
author_rank: Newbie
timestamp: November 10, 2023, 05:15:00 pm
content: A picture of the back of the lamp. Right under the text you can see 3 resistors , these are at the beginning of each of the 3 led strips.

author: Zero999
author_rank: Super Contributor
timestamp: November 13, 2023, 08:25:44 am
content: What are the part numbers of the ICs on the board which works?What's the supply voltage?Assuming it's mains, it's probably just a linear regulator. Is there any electrical separation?

author: mircea L
author_rank: Newbie
timestamp: November 13, 2023, 10:04:31 am
content: I managed to find a strong magnifying glass and am now able to read the part numbers.Also I have taken a picture of the whole board.The input that comes into the board is mains (220) and the output to the array of leds is 258v , 52mAThe lamp itself has quite a few features , it has a light sensor , presence sensor and also remote radio capabilities.I however don't need to use these ... just the plain lamp.The IC that is doing the LED driving is LNK306DN -https://pdf1.alldatasheet.com/datasheet-pdf/view/527621/POWERINT/LNK306DN.htmlAnd then there is also a PIC - PIC16F886 which drives the radio and probably the presence sensing featuresThere is also an optocoupler which is linked on the FB pin of the LNK306DN chip

author: Zero999
author_rank: Super Contributor
timestamp: November 13, 2023, 05:49:50 pm
content: My advice is to repair the power supply. The parts are widely available. It will still be possible to get it to work, whether or not the microcontroller or receiver work.The circuit is probably similar to one of the ones given on the LNK306DN data sheet.What other parts are bad?Warning there's no electrical separation between the mains, the LEDs, microcontroller and receiver. All parts of this circuit are live at mains voltage!

author: mircea L
author_rank: Newbie
timestamp: November 13, 2023, 09:04:36 pm
content: Yes, thanks for the advice , that is what I will try to do , I will try to repair this power supply , seems like a fun thing to do.I have annotated in the picture the parts that I found to be bad.As I mentioned in the intro , I don't care about the fancy stuff this lamp has , I just want to make it work as a normal lamp.For now , it's a puzzle to me how is the sensor / remote ( smart side of the lamp ) turning on/off the power supply to the LED'sIs it doing that via the Optocoupler that is linked on the FB and BYpass pins of the LNK306 ?ThanksMircea

author: Zero999
author_rank: Super Contributor
timestamp: November 14, 2023, 08:21:59 am
content: Obviously replace those parts.What about the 5 pin semiconductor next to those shorted capacitors?The main problem is determining the capacitor values. Often it's possible to guess them by looking at the data sheet for the IC they're connected to. If it's across a power supply rail, it's just for decoupling and not critical. You could also remove them from the working unit, measure them, but you need to be very careful not to damage the PCB or lose any parts.