Faulty LED driver (BREL-2D-36T)

[Cirkit]

I am trying to repair this constant current LED driver.

The output diode (MUR460) is reading a forward voltage of 0.071V and a reverse voltage of 0.087V. The forward resistance is 197Ω and the reverse is 218Ω. So clearly faulty.

I have also measured the 330μF output smoothing capacitor and it reads 297μF.

What would cause the diode to fail in this way and should I replace the capacitor even though it is within 20% of the marked value?

Does an ultrafast diode have to be used?

 

[bertus]

Hello,

Did you measure the diode out of circuit?
An in circuit measurement may fool you.

Bertus

 

[Cirkit]

Hello,

Did you measure the diode out of circuit?
An in circuit measurement may fool you.

Bertus

Yes both measured out of circuit.

 

[bertus]

Hello,

When it reads a short out of circuit, the diode is faulty.

Bertus

 

[Cirkit]

What would cause the diode to fail in this way? Does an ultrafast diode have to be used?

Do you think I should also replace the capacitor?

 

[bertus]

Hello,

There will be a cause of the failing of the diode.
I also see a three legged element.
It could be a transistor or mosfet that failed too.

Bertus

 

[cjdelphi]

What would cause the diode to fail in this way? Does an ultrafast diode have to be used?

Do you think I should also replace the capacitor?

it's a high frequency transformer so best to use a schottky diode or you risk it acting like a resistor

what blew it up, my guess would be an inductive voltage spike from the inductor maybe? check the transistor for a short while you're at it...