In article <LLydnV7NW6y3UyLVnZ2dnUVZ_orinZ2d@[EMAIL PROTECTED]
>,
"Dave" <db5151@[EMAIL PROTECTED]
> wrote:
> "Eeyore" <rabbitsfriendsandrelations@[EMAIL PROTECTED]
> wrote in message
> news:48BFC5D3.566F1BA9@[EMAIL PROTECTED]
> >
> >
> > Dave wrote:
> >
> >> It seems to me that a flourescent ballast is probably just a
transformer
> >> and
> >> a high-voltage electrolytic cap. And when it "goes out" it's
probably
> >> because the cap failed. If these are true, could I just replace the
cap
> >> and
> >> make it work again?
In all of the flourescent fixtures I've seen that use a cap, it was just
a small ceramic disk capacitor wired across a little NE-4 or similar
bulb, both contained in the easily replaced "starter" can. (But those
were *OLD* fixtures - At least 20 years old) No caps to be seen anywhere
else in them.
> >
> > If you were that bothered. Like to see you get the right type though.
> >
> > Why not replace it with an electronic ballast ?
> >
> > Graham
> >
>
> Yeah... My Scottish soul hates to throw away anything that might be
fixable
> though. Still. Are there different types of caps for ballasts?
Probably
> not worth bothering with...
>
> Thanks,
>
> Dave
The failure mode I've always seen with dead ballasts has been breakdown
of the coil insulation, usually resulting in a short/arc between the
secondary and either the core or the case (or both, since most of them
seem to have the core and the case electrically connected, either
intentionally via a lug on the core with a strap to the case, or
incidentally because the core was laying directly on the case) of the
ballast.
The ones I've taken apart have all been buried in potting compound, and
I have yet to see one with a cap inside the unit that could be replaced.
Last year, we had the ballast in an 8 foot fixture die, and it came
scary-close to burning down the barn - I walked in for evening feed
after one of the boarders had left the aisle lights turned on for most
of the day, only to encounter the stench of "on the edge of starting to
burn"-hot tar, a buzz like a swarm of angry bees, a cloud of smoke
hovering near the ceiling, tar "icicles" dripping out the end of the
fixture, and a puddle of tar on the floor below it. After killing the
circuit and inspecting, found that the ballast had overheated to the
point of blowing the potting compound all over the inside of the
fixture, and the ballast case had most of its paint burned/scorched off
it, with the metal obviously heat-discolored. It was so hot that
touching it would have been good for at least a blister. That led me to
checking the hayloft for hotspots, where I found that the 3/4 inch
plywood decking that makes up the ceiling/hayloft floor was so hot above
the failed unit that the plywood had started to de-laminate. Once the
fixture was removed for replacement (I sure wasn't going to diddle
around with trying to repair the thing with all that potting compound
splattered everywhere) found obvious scorching on the downstairs side of
the plywood. *WAY* too close for my liking...
--
Don Bruder - dakidd@[EMAIL PROTECTED]
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