[Test-Equipment] Exploding capacitors ? (wavetek 114s)

[Cmos]

John,

I don't know how long it has been sitting, as I got it
as-is a few weeks ago.
But, this dose seem to be the most likely cause, as
other things(voltage, load, ect.) seem to be ok.
It was an axial cap. made up of a plastic tube with
the ends sealed with a very hard epoxy type stuff.
Also, there was fluid that blow all over the boards
when it exploded, so it was not dry. It was also 
quite hot, as well as another one for the other
polarity(was a +/- 12volt supply).
So, steam pressure sounds like the cause. 

I think I am going to replace both these caps and
two other ones about the same size in another
part of the power supply. 

Jim Martz,

> Cmos wrote:
> 
> > Hi all,
> >
> > Was just looking at a Wavetek 114s sweep genorator. I had taken the cover off
> > and was testing
> > the different outputs to see if I could get any output on anything, was not
> > getting anything. Then,  with out worning(smoke or otherwise), BANG... and a
> > cloud of smoke.
> >
> > A sealed plastic electrolitic cap.(2,000mf) about 1" round and 3" long,
> > literly exploded. Shards of plastic flow all over the room, lukely I was not
> > wonded, as my face was only a foot from it.
> >
> > Has any one else experenced this?
> 
> Yes. See the photo section here:
> 
> http://www.trackpads.com/webs/wireless-set-no19/index.htm
> 
> > Ok, now to the point of this email. Why did it explode ? This was a filter
> > cap. in the power supply. ....
> 
> The most probable reason is the equipment had not been used in a long time and
> the cap had gotten flaky. When power was re-applied from a low impedance source,
> the heat generated by the leakagevcurrent flowing through the cap caused it to
> heat up and make steam. The thing popped because of the steam pressure.
> 
> The moral is reform caps that have sat a long time (or replace them). Even caps
> that have sat idle for 60 years can often be rejuvenated.
> 
> -John
> 


-------------------------------------------
Jim Martz,
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