On 26/03/2018 16:08, Camiel Vanderhoeven wrote:
4B would be a 2.2V zener; 4A would be a 2.0V zener, so that’s odd indeed...
That's the idea I had...
Except it's not a zener, or at least not anything like those. I took
one out of another (working) supply, and I can tell it has a forward
voltage of 0.2V, so it's presumably a Schottky diode of some sort. I
can also tell it's not a low-voltage zener; the reverse breakdown
voltage is more than 35V (the highest my bench supply goes up to).
I'm hoping I don't have to breadboard a 1kV supply and find a lot of
multi-megohm resistors to try and estimate the breakdown voltage - and
then guess at the forward current rating.
On 3/24/18, 9:47 PM, "cctech on behalf of Pete Turnbull via cctech"
<cctech-boun...@classiccmp.org on behalf of cct...@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
