Thanks. Will bear that in mind. I can check for physical faults, continuity and Ohms fine but not so sure on component readings and values.
Generally speaking, that’s all you need to really be testing to find the fault. Here’s the approach I would take if it were me trying to find the problem:
- Open the fixture and examine the circuit boards. Look for anything obvious like loose wires, cooked components, or similar.
- With power applied to the unit and the defective LEDs on, gently probe the circuits to see if a putting pressure on a particular spot improves or exacerbates the issue. This will help identify bad solder joints or cracked wires. Care should be taken to avoid being shocked since you’re working inside energized equipment.
- If still no answers, unplug the unit and examine the LED PCB. Identify the circuitry in use (i.e. all LEDs in parallel, multiple “branches” of LEDs in parallel, etc.). Try to isolate the bad LEDs and see if there’s commonality in the circuit, such as them all being on the same “branch”.
- Test the diodes individually. “Good” diodes only pass current in one direction. If your multimeter has a diode testing mode use that, otherwise the resistance meter will work. If a diode passes current in both directions it’s bad and needs to be replaced. If the diode shows abnormally low or “0” resistance in its “forward bias” direction it’s also bad and needs to be replaced. Since the specific numbers can vary by LED make/model and the measurement you’re taking, start with some known “good” LEDs as baseline data before looking for the bad ones. My hunch is that this is the step that will identify your problem.
- If still no luck and every diode shows consistent results and proper bias, the problem lies upstream. Try the procedure above and report back before going down this rabbit hole. Good luck!
