TU56/TC11 restoration - Power supply question

Ashley Carder wacarder at usit.net
Wed Mar 16 15:44:53 CST 2005

>    Apart from the shock (and dangerous sudden-hi-energy discharge) risks - 
> one thing to be aware of when 'bringing up' large analog power supplies is 
> the condition where the filter capacitor(s), or other big electrolytic 
> device, develops and internal short, or loses it's chemical polarization, 
> and the esuing thermal rise causes the case to burst.  Most big caps have 
> built-in rupture vents, or a strategic 'crease' in the aluminum to keep 
> this from becoming an explosion - but I have been the unfortunate 
> recipient of more than one suddenly-exploding capacitor.
>    Not counting the sheer terror of having something go BANG! right next to 
> you, the larger units can store considerable energy, both pressure and 
> electrical, and I've seen them do a lot of damage, especially the ones 
> mounted upside-down, which have a tendency to launch off the chassis like 
> a mortar shell and poke holes in walls.
>    Then there's the hideous mess that all the 'guts' of the cap makes when 
> they explode and puke up all over everything.
>    So the moral of the story is to bring a long-dormant power supply up 
> slowly, using a variac and loads, and to be vigilant for any signs of cap 
> leakage, swelling, getting suddenly warm, or hissing sounds coming from 
> one.


Thanks for the vivid visual images!  I suppose I've been lucky so far.
Actually, most all of the stuff I've acquired has recently been powered on
by someone else before it came into my hands, so if it was going to go
BANG!, it probably would have done so before it came into my 

I'd be interested in hearing any horror stories relating to exploding
capacitors and more info on the proper caution that needs to be
exercised when messing with old power supplies.


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