TU56/TC11 restoration - Power supply question

[John Lawson]

On Wed, 16 Mar 2005, Ashley Carder wrote:

>
> I am aware of the risk of shock because they can hold a charge for
> a while until they are discharged, but are there other things that I
> need to be cautious of?  Can't they leak and ruin things, just like a
> battery?  What else should we look out for related to the power
> supplies?

   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.

Cheers

John