VAX-11/750 power supplies
mattislind at gmail.com
Wed Apr 8 15:23:42 CDT 2015
BTW. The same type of diodes are supposed to be found in H7140 PSU of the
PDP-11/44. If anyone out there has a 11/44 and is able to confirm what
diodes are used in that one it would be interesting.
2015-04-08 21:37 GMT+02:00 Mattis Lind <mattislind at gmail.com>:
> 2015-04-08 18:46 GMT+02:00 tony duell <ard at p850ug1.demon.co.uk>:
>> > However looking in the print set the diode is listed as 1114197-00 with
>> > 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:
>> > /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.
> The problem I have it is impossible to confirm what the rating is for this
> diode. I simply cannot find the data sheet.
> The 5V PSU uses four of these diodes and the max output is 135A. The 2.5V
> PSU uses three diodes and the max output is 85A.
>> 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 Schottky diodes without problems.
> I will try to run it with the replacement USD5096F that I have and see how
> long it lasts. It probably depends on how many boards I stuff into the
> machine. If that fails I will search for DO5 mount 60A Schottky diodes. If
> anyone has a bunch of them at a good price I am interested!
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