HP9915B with PSU problems

[Bjørn]

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