20 Mar
2005
20 Mar
'05
2:47 a.m.
On Sun, 20 Mar 2005 01:24:35 +0100, Tony Duell <ard at p850ug1.demon.co.uk>
wrote:
HP really loved to use silly value capacitors in their PSUs for no good
reasons as dar as I can see. The tolerance on an electrolytic is
typically something like +/-20%, or even +50%/-20%. Which makes me wonder
why I have a PSU board with an assortment of 5600uF and 6000uF caps on
it. As another example, the 9845 PSU contains som 810uF caps -- 820uF is
a prefered value. Hmmm...
Given what I know of HP engineering, I suspect that there is a reason for
the differences.
In a power supply, it is not only the capacitance that matters. The
slightly lower value might be what you get when you make a lower reactance
version of the same capacitor. Or it might be a more rugged version, or a
higher temperature version.
This might even be something the manufacturer had not planned for, but the
HP engineers discovered during component testing and qualification.
--
-bv