TRS-80 Fireworks

Matt Burke matt at
Wed Aug 28 03:34:05 CDT 2019

On 28/08/2019 09:15, Marvin Johnston via cctalk wrote:
> I'm just curious how many people have powered up their TRS-80
> computers, and ended up with a bang and a room filled with smoke?
> So far, I've gotten the fireworks in two out of two TRS-80s (model 3
> and 4) when they were powered up. In both cases, the problem was with
> the main line filter capacitor mounted on one of the power supplies.
> The computers continued to work which was my first clue the problem
> was not serious :).
> Is this a normal problem with these older computers? I'm used to
> seeing the electrolytics give problems, but this is the first time
> I've seen one of the X type line filter caps blow.

This is very common for these paper line filters. I've had the same
failure with an Osborne 1, DECserver 200, DELNI and PDP-11/73. There are
many more devices that have them; generally anything with an Astec brand
power supply. I replace them before even powering up these days.


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