TU56/TC11 restoration - Power supply question

[Eric Smith]

Ashley wrote:
> I read the page on reforming capacitors.  Quite a good document.  Now
> I just need to take a refresher physics class so I can totally understand
> it.

When the electrolytic capacitor is first manufactured, it has to go
through a "forming" process to grow a thin layer of oxide on one
electrode.  This oxide layer is the dielectric.  It is formed by
application of current-limited DC.

If the capacitor is unused for an extended period of time, the oxide
layer breaks down.  At that point if a DC voltage is applied that is
not limited to a relatively low current, it will punch through at the
point that the oxide is the thinnest, resulting in permanent damage.

Provided that the capacitor has not failed either by leaking, the
electrolyte drying out, or punch-through, applying current-limited DC
will reform the oxide layer, restoring the capacitor to a useful state.

Eric