SGI Indy power supply: identify this diode?

Mon Mar 26 10:08:12 CDT 2018

4B would be a 2.2V zener; 4A would be a 2.0V zener, so that’s odd indeed...

Camiel

On 3/24/18, 9:47 PM, "cctech on behalf of Pete Turnbull via cctech" <cctech-bounces at classiccmp.org on behalf of cctech 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