SGI Indy power supply: identify this diode?

[Bob Smith]

4BSOD-123F MM1Z2V2SemtechZener diode

http://www.s-manuals.com/smd/4b

On Sat, Mar 24, 2018 at 4:47 PM, Pete Turnbull via cctalk
<cctalk at classiccmp.org> wrote:
> After a recent power cut and a series of glitches as the power was
> restored, one of my Indys suffered a PSU failure.  It's a Sony APS-81 171W
> unit, SGI P/N 060-0008-001.  I've found half a dozen damaged parts, and I've
> identified a 150R 1W metal film resistor (R135), two trannies (Q105, a
> 2SC4304 and Q106, a 2SC2785) and a couple of small diodes.  One of them
> (D116) appears to be a 6.2b2 (6.2V 1/2W) zener.
>
> The other one I'm not sure about.  On the PCB it's labelled D113, and
> it's adjacent to the 2SC2785.  It's very small, with a green band at the
> cathode end, and the legend "4B" in green - photos at
> https://www.flickr.com/photos/pnt103/albums/72157667056183978
>
> Oddly, another Sony PSU I looked at had a diode there that looked
> identical except it's marked "4A".
>
> I have an idea what it might be but if anyone actually knows what family
> or type/value this is, I'd be grateful for any insight.
>
> --
> Pete
> Pete Turnbull