Article View: sci.electronics
Article #5122Re: question about computer power supply
From: Larry Lippman
Date: Sun, 15 Jul 1990 23:27
Date: Sun, 15 Jul 1990 23:27
29 lines
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2141 bytes
> >I recently bought NCR PC-6 power supply to power some hobby projects. When I
> >received the supply, I measured the outputs. The +12V line measured +4.95V
> >and +5V line measured +4.8V. I have been told that the +12V line will not
> >be +12V until a load is connected to the supply. I was told that the scheme
> >was somewhat like the IBM 'goodline', whatever that is.
>
> I don't know about that NCR PC-6 supply,but I do know that the IBM
> power supply gives the expected voltage without a load being apply,if my
> memory serves me right.So in that case,I would assume that maybe something
> is wrong with that NCR job you have.
I have no specific knowledge of the NCR PC-6 power supply, but I
would like to point out something that I have seen on other computer power
supplies which *could* be your problem.
Some well-designed power supplies provide an external sense lead
which is connected to a terminal on the PC-board backplane. This will
automatically compensate for any IR drop between the supply and the
backplane. If your power supply has a multi-pin connector whose pin
functions are not explicitly labeled or otherwise known, it may be that
one or more pins are for sense purposes.
Failing to connect a voltage sense lead to the power output lead
will result in an incorrect voltage with lack of regulation (usually, but
not always a *lower* voltage).
Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?"
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!samsung!zaphod.mps.ohio-state.edu!sunybcs!kitty!larry From: larry@kitty.UUCP (Larry Lippman) Newsgroups: sci.electronics Subject: Re: question about computer power supply Summary: Beware of unconnected power supply "sense" line Keywords: computer power supply Message-ID: <3852@kitty.UUCP> Date: 15 Jul 90 23:27:47 GMT References: Experience <30733@eerie.acsu.Buffalo.EDU> Distribution: sci Organization: Recognition Research Corp., Clarence, NY Lines: 29