SGI Indy power supply: identify this diode?

Pete Turnbull pete at
Sun Apr 8 11:51:09 CDT 2018

On 26/03/2018 17:07, Pete Turnbull via cctalk wrote:
> Except it's not a zener, or at least not anything like those [ones
> Camiel and Bob suggested].  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).

So I dug out my Avo 8, set to the 50µA range, hooked a matching diode 
from another Indy PSU up to a 300VDC supply via a couple of 1Mohm 
resistors and a 2Mohm pot as a voltage divider.  I found that as I wound 
the pot up from zero volts, the reverse leakage current rose abruptly 
from 2-3µA to a few tens of µA at about 59V across the diode, and the 
voltage across it dropped a little as I wound the pot up further.

So I think it's a Schottky rectifier diode, with a PIV rating probably 
between 50V and 60V.  Of course I have no idea what the current rating 
might be, and I can't think of a simple safe way to work that out.

Any comments?

Pete Turnbull

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