VAX-11/750 power supplies

tony duell ard at p850ug1.demon.co.uk
Wed Apr 8 11:46:30 CDT 2015


> However looking in the print set the diode is listed as 1114197-00 with the
> remark "60 AMP POWER SCHOTTKY DIODE"
> 
> Is the Unitrode USD5096F a 60 Amp diode? This link tells me it is a 35A
> diode:
> 
> http://www.electronicsurplus.com/unitrode-usd5096f-diode-35amp-35v-piv
> and so does this link:
> http://www.ebay.com/itm/35-Amp-35-Volt-Stud-Mounted-Diode-with-Wire-and-Lug-Wind-and-Solar-Blocking-
> /271653646843?pt=LH_DefaultDomain_0&hash=item3f3fd1b1fb

It's possible (although unlikely) that DEC selected diodes that could stand 60A for this location from what were
nominally 35A parts. More likely, I think, is that what is _needed_ here is a 35A diode (what is the output current 
of this PSU) and that the originially specified part was a 60A one (which is clearly be OK). Then somebody found
a 35A part that would work.


Of course you can always fit a higher current diode than is strictly required (provide the switching times are
fast enough in a circuit like this). My guess is that since diodes have improved since the days of the 11/750,
you could fit modern 60A shottky diodes without problems.

-tony



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