Hello there! I'm trying to repair a LED emergency light but I've found a problem. I have 2 of those lamps (one works fine and the other doesn't). I think I've identified the problem but there are components with no markings so I can't identify them. (See photo.)

My questions are the following:

1. How do I identify which diode is this (in red)? My guess is that it is just a fast schottky diode, but which model?
   
   
2. If my guess is correct, can I put a 1N4148 (DO-35) instead?
   
   
3. How do I identify the zener diode (in yellow)? Measuring with a multimeter I read 3.5v across it. My guess is that it is a 3.6v zener diode since they are available in the market and with that package (SOD-80).
   
   
4. If my previous guess is correct (or not), can I replace that diode with other (same zener voltage) but with a DO-35 package?
   

Yes, I'm speaking of replacing because that zener diode is shorted in the light that doesn't work. All measurements were made in the one that works. And respect question 2, that diode is missing in the lamp that doesn't work ._.

 

If you have a working unit, measure the voltages across the diodes while the power is on.

 

Have you got a full picture of the pcb...the Yellow diode is marked as TM/ W1..?

 

Or it could be "W1"....

 

I would more suspect that a bad LED light is causing your problems. You're measuring the unknowns "in-circuit" and aren't showing us even half of what we need to make any diagnosis.