IBM 5155 Power supply schematics or info
ard at p850ug1.demon.co.uk
Wed Nov 16 18:48:53 CST 2005
> > I think that would be OK. While it's a bad idea to randomly make
> > adjustments, you are not doing that. You have a fairly clear idea of
> > what's going on, and what that trimmer adjusts.
> As soon as I touched the trimmer, I discover the problem !! The cursor was
> instable !!
> The outputs voltages changes only posing the screwdriver on the trimmer.
Now yuo know why HP (and others) didn't put trimmers in their PSUs (or
anywhere else that they could avoid). They had select-on-test resistors,
or resistors that you clipped out to set the voltage. Typically you'd
start with all the resistors installed (giving the minimum output
voltage), measure that voltage and look at a table in the service manual
that told you which resistors to cut out.
The big advantage, of course, was that you didn't get contact problems
> Now, with a new trimmer (a good Beckman) the voltage in full adjustable in
> the range.
> I have tested this power supply with various load and the regulation on 5V
> and 12V is good.
> I'm writing a web page with all your notes, my experience, photo, schematic
> and data sheets.
All I ask is that my name remains somehow associated with the schematics.
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