16 Mar
2005
16 Mar
'05
1:25 p.m.
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