TRS-80 Fireworks

Mark J. Blair nf6x at
Sat Aug 31 00:27:26 CDT 2019

> On Aug 28, 2019, at 2:07 AM, Guy Dunphy via cctalk <cctalk at> wrote:
> An extremely common problem with all old electronics from around that era.
> The mains filter caps are commonly 'RIFA' brand metalized polyester film,
> encapsulated in a clear-honey-coloured resin. 
> The problem is that the resin embrittles and shrinks with age, resulting in
> many small cracks. (And sometimes large pieces falling off.)
> The cracks let in moisture, which absorbs into the insulating film.

I suspect those notorious Rifa brand capacitors would not be so problematic if they had polyester film dielectric. But if I'm not mistaken, they don't; they have *paper* dielectric!

Aside from that one correction, I agree with everything else you wrote about the likely failure mechanism of these evil little rectangles of compressed smoke and fire.

Mark J. Blair, NF6X <nf6x at>

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