what is this part?

[vixo]

I think this part says BD4 5C14 but I can't find in any database a reference for this part code, does anyone know? Help much appreciated!  

[Zenith]

Which equipment is a part of? That may help shed some light on it. Can you get the manual for the equipment?

Looking at the picture it appears to be designated D4, which suggests it's a package of diodes.

[Daixiwen]

Doesn't D4 apply to the diode in the bottom left hand corner? The reference designators on that silkscreen are a bit all over the place

[Psi]

Logo might be Torex Semiconductors

[mengfei]

might help
good ol Picasa 3 functions

[Psi]

Definitely looks like Torex Semiconductors, you can now see the curve of the line

Pretty sure the package style is called MSOP-10 by Torex

[mengfei]

Definitely looks like Torex Semiconductors, you can now see the curve of the line

which country is Torex originally from?
Heard before but never came across some of our projects

[Psi]

If you go here and then click "Products using this package" you find some things that could be it
https://product.torexsemi.com/en/packages/msop-10


Ground is on pin9, which is correct.  But i cant match up any of the part numbers to the part numbers on the chip.
Its possible its an older obsolete/previous version of these IC's

Check what pins that inductor to the right is across, and match them up to the datasheets.

[janoc]

That pin 4 soldering looks a bit dodgy. If that IC is causing problems touch the soldering up.

[wasedadoc]

Looks more like 3B4 to me.

[fzabkar]

I'm not sure about this one ...

https://product.torexsemi.com/system/files/series/xc9502.pdf

It's a different IC, but the marking codes for the XC9128/XC9129 might provide clues. For example, it appears that the feedback voltage is 0.45V.

https://product.torexsemi.com/files/status/xc9128.pdf

Edit: Could "3B4" be "8B4", in which case the IC could be XC9128B45CAR?

http://markingcodes.com/search/c/8b4

8B4+5CXX --> XC9128B45CAR