Zener 3T 4148 voltage rate

[sdancer75]

I couldn't find anything....

I need to replace a burned zener. It is marked 3T 4148 if I read well.

How much is the reverse rating  voltage?

Thanks

[madires]

Maybe a standard 1N4148, and not a Zener?

[sdancer75]

It seems like a zener. Orange glass is classic package for zeners but how can I be sure? Its from smps and it's on the primary side just before the optocoupler

[madires]

Then reverse-engineer that part of the circuit to figure out what the diode is meant for.

[sdancer75]

Looking again the part under my microscope, I can say it says ST4148 and not 3T4148 I mentioned originally. I google it and I found that it's a switching diode despite the fact that many alibaba and aliexpress webpages describe it as zener.

So, I suppose I can safely replace the part with the 1N4148. Do you agree?

[madires]

Yep!

[wraper]

Orange glass is classic package for zeners but how can I be sure?

It's not solely for zeners. If it has 4148 written on it, it's 1N4148. Zeners have different marking.

[fzabkar]

See the references to ST4148 in the following circuit diagrams:

https://www.abcelectronique.com/forum/attachment.php?attachmentid=66088