WTB: Tower case for IBM model 80, 60 or 65 (PS/2)
ard at p850ug1.demon.co.uk
Wed Sep 21 19:01:27 CDT 2005
> On 9/21/2005, jpero at sympatico.ca wrote:
> >I was advised that to change this 220VAC unit to 115VAC would
> >not work even I knew what exactly to do just install voltage doubler circuit.
> I got the same story from an IBM marketing rep when I wanted to take
> an (original) US-use PC to India to run on 220v 50Hz. He was right,
> but for a reason that I hadn't considered.
> In the old 60w PC power supplies, the fan is AC-operated and is
> specific to the line voltage stamped on the nameplate. I simply
The IBM PC and PC/XT power supplies that I've seen over here are, of course,
designed for 230V mains. I am pretty sure they're made by Zenith. From
what I remember, the fan is a 12V DC one but there is a mains-frequency
transformer with a 115V primary (!) connected between one side of the
mains and the centre-tap of the mains smoothing capacitors. A bit of
thought shows this is OK...
There is an internal link that converts the input rectifier to a voltage
doubler and in the process connects this transformer across the mains. In
other words it sets it for 115V.
The PortablePC is similar, but there's a user-accessible switch to set
the input voltage. It does much the same as the intenral link on the
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