Electronics > Beginners
Please help identify this SOT23 diode?
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ocset:
Hi,
We have an offline  LED  lighting product from  an old company. It had been  running on the mains for two years.
It has a high voltage linear regulator just downstream of a mains diode bridge (there is no smoothing capacitor after  the diode bridge) . The regulator output is 2.5V. It just supplies a microcontroller. Connected from output to input of this regulator, is a SOT23 diode. This diode obviously stands off the rectified mains haversines (339Vpk).

An ex member of staff assures us that this diode is a BAS16……but BAS16 is only rated to 100V.     The diode itself is still functional,  and is pinned out like a BAS16. But surely such a low voltage diode wouldn’t have been able to survive going across the mains?

The diode has markings on it…….”kJB” ( or it might actually be “kJ8”)…and then perpendicular to this, it is marked “CN”.
Does anyone know what actual diode this might be?

BAS16 datasheet
https://www.vishay.com/docs/85539/bas16.pdf
mvs:

--- Quote from: treez on November 21, 2018, 07:44:07 pm ---The diode has markings on it…….”CJB” ( or it might actually be “CJ8”)…and then perpendicular to this, it is marked “CN”.
Does anyone know what actual diode this might be?

--- End quote ---
CJ mark is used for mmbz4683, 3V zener diode.
"CN" is probably logo of ON semiconductor.
floobydust:
Consider instead NXP TL431BQDBZR, SMD marking code "CJ%"
ocset:
Sorry, Ive a massive apology to make....it is marked "KJ8" (or "KJB") and not "CJ8"

...I was in the dept till late last night and had to leave before id got a good look.

Im pretty sure no SOT23  diode in the world is rated for mains voltage?

Aaah...solved it, its a 400v rated MMBD5004S, and it was made in Nov 2015
nali:
Try Googling "KJB" and "SOT23"? The very first hit gives MMBD5004, which is a 400V reverse breakdown part, the second hit gives the datasheet.

HTH
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