repairing a DEC VT420

From: Don Maslin <donm_at_cts.com>
Date: Wed Jul 18 19:38:35 2001

On Thu, 19 Jul 2001, Tony Duell wrote:

> >
> > +AD4- J +AD0- tolerance (which I can't remember, 10+ACU-?)
> >
> > Don't eliminate +ACI-Joule+ACI- from consideration.
> > Seems like it would be one useful measure of
> > a Cap. (Uhhhh, Tony?)
>
> Not really. While capacitors do store energy (measured in joules), the
> energy stores is 0.5*C*V^2. So to know the energy stored in a capacitor,
> you have to know the voltage. I have never seen a capacitor rated in
> joules (meaning the amount of energy that can be stored at the maximum
> working voltage of the capacitor) although it might makes sense for
> things like photoflash capacitors.
>
> One other unit we can discount is the 'jar'. This is actually a unit of
> capacitance, IIRC, 1 jar = 1/900 uF. It was used by the (British) Royal
> Navy (amongst others) until the mid 1930's IIRC. I have a few books which
> give capacitor values in jars.

Perhaps so named in deference to Leyden's original jar capacitor?

                                                 - don

> I think, though that on any piece of computer hardware it's safe to
> assume the capacitors will be marked in some fraction of the farad and
> the resistors marked in some multiple of the ohm.
>
> -tony
>
>
Received on Wed Jul 18 2001 - 19:38:35 BST