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Electronics => Repair => Topic started by: CrazyTiger on August 24, 2019, 07:20:18 am

Title: Help me Identify this component by ST
Post by: CrazyTiger on August 24, 2019, 07:20:18 am
Hi,

I have this diode by ST which is shorted as someone fed 240AC to the 24v DC line.

(https://i.imgur.com/pCnJDxc.jpg)

I believe its a bidirectional TVS diode, the marking is BEX. Can anyone suggest what would be the part number for this.
 My first guess is it might be SM15T39CA.
https://www.st.com/resource/en/datasheet/sm15t.pdf (https://www.st.com/resource/en/datasheet/sm15t.pdf)

Is there any other possibility?
Title: Re: Help me Identify this component by ST
Post by: fzabkar on August 24, 2019, 07:35:05 am
It looks correct, but I'm wondering why the designer didn't choose a 24V unidirectional diode, assuming it is connected across a regulated 24VDC supply. A bidirectional diode affords no real reverse polarity protection, and a 40V breakdown voltage might be too high for the circuit.  :-//