DEC H7822 power supply

Maciej W. Rozycki macro at
Thu May 12 10:39:27 CDT 2022

On Wed, 11 May 2022, Paul Koning wrote:

> > I guess especially for standard capacitors factories ordered whatever was 
> > readily available whereas with the high-ripple low-impedance/ESR parts the 
> > choice was much more limited.
> I wonder if nowadays a good replacement for the case where low ESR is 
> needed would be a big ceramic capacitor.  Unlike the old days those now 
> can be had in many-µF capacitances.

 Possibly, in the lower capacitance range, if not for the horrendous 
price, e.g. $50/£40 each for a 470µF/25V part: 


(at least you get free shipping for just one piece).  There's still little 
choice for the higher range parts found in DEC PSUs, such as 1800µF/25V, 
4700µF/10V or 6800µF/20V even.  With aluminium organic polymer capacitors 
rated voltage also quickly drops for higher capacitances, so you won't get 
any of these as replacements either.  I don't know offhand to what extent 
these limitations come from current technology vs the laws of physics.


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