Re: Apple III power supply capacitor replacement

["Michael J. Mahon" <mjmahon@aol.com>]

Patrick Schaefer wrote:
> schmidtd schrieb:
>
> > Given the exploding capacitor problem in a /// power supply:
> > http://i421.photobucket.com/albums/pp293/groinkhi/IMG_0191.jpg
> > there were some recommendations on the size/capacity/rating/type that
> > would be appropriate here.  What were they, again?
>
> 220nF is written on the capacitor, 100nF should work as well. You can 
> also just remove the part and accept the higher EMI emission level -- 
> this old machine doesn't fulfil the CE requirements anyway.
>
> In any case the "X2" rating is important. This means suitable for direct 
> connection across the mains supply. You cannot use a regular 400 or 630V 
> MKP/MKT here.

All true, but there is also a protective function of the capacitor.  It
low-passes short spikes on the power line that could damage the bridge
rectifier, too.

Anything within a factor of two of the design value should be fine.
Using too large a value will subject the fuse to inrush current spikes,
possibly shortening its life, as well as increasing the capacitive
line current flow, which is mostly a power factor issue.

-michael

NadaNet 3.0 for Apple II parallel computing!
Home page:  http://home.comcast.net/~mjmahon/

"The wastebasket is our most important design
tool--and it's seriously underused."