VAX-11/750 power supplies

[Pontus]

On 04/08/2015 10:23 PM, Mattis Lind wrote:
> 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.

I have.. but it's darn hard to get too at the moment.

/P

>
> 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
>>> 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.
>>>
>> 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!
>>
>>
>>> -tony
>>>
>>> /Mattis