Troubleshooting 50w LED Floodlight: Multimeter Checks, Steps & Key Components

Hello. A colleague tossed me this LED floodlight. So I'm writing here because I don't know where to start. Maybe someone will direct me where to start checking with a multimeter. Thanks in advance

zubek_1990 wrote:

Maybe someone will direct me where to start checking with a multimeter.

From determining the beginning and end of the diode chain, and measuring the DC voltage between these points.
Voltage is - diode (diodes) on
Voltage out - converter damaged.

Be careful - you work with an uninsulated device from the network.

On a good day I would not connect this floodlight to mains voltage! As you can see from the attached photos, the topology of this LED matrix is 2P27S, i.e. two LEDs in parallel connected in a 27-element series. Do all the LEDs emit light? I assume so. Probably one of them fell ('the weakest link'), the other went twice as much current, which immediately damaged it. Hence the break in the series and the lack of light emission.

On a good day, a multimeter in the paw and checking each of the LEDs - from experience I know that this is the most common cause of failure (especially if the floodlight cooperated with a motion sensor). In addition, it is also worth checking the input fuse resistor (Fuse Resistor). The next step is to verify the power supply system of these diodes.

I measured the voltage on the diodes and they look like this:

Ps when measuring voltages with a meter a few of them began to dim very weakly, so exactly a millimeter dot on the diode

Maybe a colleague explain how he measured these tensions? With the luminaire connected to the power supply? Did each of them emit any light?
It seems that only those pairs of LEDs with a voltage of ~ 6.0 V are ok - the rest is damaged.

I would suggest to check each pair of LEDs separately by setting the diode test mode on the multimeter. Each of them should emit light. Missing is either a break or a short circuit. Use a marker to mark those that are inflexible.



Does your friend have a DC power supply, e.g. 5.0 VDC? You could choose a suitable resistor (22 Ohm / 0.5W) and power each pair of LEDs through it. Then you will catch the crap on the bank.

Ps. Some of them began to glow slightly because you were closing a circuit through which a small amount of current flowed, sufficient for this minimal light emission.

The meter I have so rather without madness, tomorrow I will see these leds according to the guide above, maybe something more I will try to give