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?  Assuming (hate that word) of course that I could get
the ballast open.  What thinks the group?  Please offer whatever laughing
criticism or encouragement you feel is appropriate.  I do not need a fire
hazard in the kitchen...

Many thanks,

Dave

If you were that bothered. Like to see you get the right type though.

Why not replace it with an electronic ballast ?

Graham

news:48BFC5D3.566F1BA9@hotmail.com...

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

Now if IIRC, the passive ballast for flourescent lights is a big
inductor which serves two purposes, the first is to store the energy
needed to ignite it (400 Volt-ish IIRC), the second is to lower the
voltage over the light to the operating voltage of the tube (which varies).

And taking a quick look on my flourescent tube over the kitchen sink,
the components are (in no particular order): Ballast/Inductor, tube,
igniter (small cylindrical thingy, say 15mm dia by 30 (or so) mm length)
and a cap. And having assembled compact flourescents, I know that some
of them come with the igniter built into the tube.

As to failures, I know that all components have a tendency to wear out,
and that at least in the bigger, tube, models, the igniter and tube can
be replaced (and should be replaced at the same time), and the other
could too (although it could be difficult to find the correct values for
the latter (have you tried the manufacturer?)).

As to electronic ballasts, they eliminate that irritating flicker on
switch-on and, IIRC, have less losses. I know that there are electronic
ballasts from many manufacturers (try Osram and Sylvania) for all sorts
of flourescents, though you might want to check with the local laws and
regulations whether it's something you can do yourself or leave to a pro.

I've seen DYI electronic ballasts schematics, in the swedish version of
Elektor, but that was ages ago (early/mid 90's).

Another point that comes to mind is the issue of RF interference, some
ballasts, DYI or not, self-installed or not, have a tendency to cause
unwanted signals in the HF band.

As to fire hazards, I have more than once seen the fire dept called out
somewhere when the ballast has overheated (usually due to leaving a
failed tube on for too long), emitting all sorts of interesting odors.

Well, that's what I can squeeze out of my brain for $.02 for the moment.

/T.

--
Teodor Väänänen                | Don't meddle in the affairs of wizards,
<teostupidity...@algonet.se>   | for you are good and crunchy with
http://www.algonet.se/~teodor/ | ketchup.
Remove stupidity to reply.     |

"Teodor Väänänen" <use.instructions.in.signat...@invalid.invalid> wrote in
message news:g9ol46$q99$1@registered.motzarella.org...

Now if IIRC, the passive ballast for flourescent lights is a big
inductor which serves two purposes, the first is to store the energy
needed to ignite it (400 Volt-ish IIRC), the second is to lower the
voltage over the light to the operating voltage of the tube (which varies).

And taking a quick look on my flourescent tube over the kitchen sink,
the components are (in no particular order): Ballast/Inductor, tube,
igniter (small cylindrical thingy, say 15mm dia by 30 (or so) mm length)
and a cap. And having assembled compact flourescents, I know that some
of them come with the igniter built into the tube.

As to failures, I know that all components have a tendency to wear out,
and that at least in the bigger, tube, models, the igniter and tube can
be replaced (and should be replaced at the same time), and the other
could too (although it could be difficult to find the correct values for
the latter (have you tried the manufacturer?)).

As to electronic ballasts, they eliminate that irritating flicker on
switch-on and, IIRC, have less losses. I know that there are electronic
ballasts from many manufacturers (try Osram and Sylvania) for all sorts
of flourescents, though you might want to check with the local laws and
regulations whether it's something you can do yourself or leave to a pro.

I've seen DYI electronic ballasts schematics, in the swedish version of
Elektor, but that was ages ago (early/mid 90's).

Another point that comes to mind is the issue of RF interference, some
ballasts, DYI or not, self-installed or not, have a tendency to cause
unwanted signals in the HF band.

As to fire hazards, I have more than once seen the fire dept called out
somewhere when the ballast has overheated (usually due to leaving a
failed tube on for too long), emitting all sorts of interesting odors.

Well, that's what I can squeeze out of my brain for $.02 for the moment.

/T.

--
Teodor Väänänen                | Don't meddle in the affairs of wizards,
<teostupidity...@algonet.se>   | for you are good and crunchy with
http://www.algonet.se/~teodor/ | ketchup.
Remove stupidity to reply.     |

Thanks much Teodor.  I think that I *will* just replace the questionable
ballast.  It's <$20.00 American, and that's not much to pay for the safety
factor (and lack of trouble.)

'Preciate it.

Dave

In article <LLydnV7NW6y3UyLVnZ2dnUVZ_orin...@posted.internetamerica>,

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.  

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 - dak...@sonic.net - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info

Yes, not your ordinary type.

Graham

news:48BFEAFE.33EDF5FC@hotmail.com...

Ahh.  Thank you.  Definetly replacement time...

Will not fiddle with it.

D

  There are several different kinds of fluorescent ballasts.

1.  Simple choke - has 2 leads, usually used with a starter (occaisionally
  a "push-to-start" switch).  There is normally no capacitor.

  When they fail, there is generally no repair other than rewinding
(extremely unlikely to be worth the time and effort), and sometimes the
core is welded together.

2.  High leakage reactance autotransformer - has 3 leads, and is
effexctively a choke combined with a step-up transformer.  Same story as
1.

  A variant is the 1-lamp trigger start ballast, which has filament
widnings added.  It is still essentially non-user-serviceable.

3.  The USA-usual "traditional" dual-4-footer - high leakage
autotransformer with a capacitor in series with the secondary.  Also has
filament windings and a small capacitor (in the ballast case along with
all other parts) to leak a small amount of current around one lamp to help
start the other when both are not conducting but voltage is applied.  The
2 lamps are in series with each other.

  If the lamp-series capacitor (which is not electrolytic) shorts, lamp
current will be somewhat high and ballast input current will be very high.

  There are similar "trigger start" ballasts for 2 2-footers.

  The case is usually packed with tar.  This one is also essentially
non-user-serviceable.

4.  Electronic ballasts - more repairable than the others, but only by
those who know how to troubleshoot and repair them *safely*.  Capacitors
may store charge, and improper repairs may add a fire risk.
  It may be difficult to verify that replacement parts are of
suitable grades (temperature rating, life expectancy at given temperature,
voltage and frequency, also failing less catastrophically, any flame
retardance/resistance) and with suitable characteristics (such as losses
sufficiently low to prevent overheating - and capacitors have 2 main
losses).
  Also, one is unlikely to repair a ballast for less (including value of
time) than to replace it.

  Bottom line:  Fluorescent lamp ballasts are generally unrepairable.

 - Don Klipstein (d...@misty.com)

news:slrngc0sav.mpp.don@manx.misty.com...

Thank you, Don.  This backs up the conclusion I had basically come to,
making me feel better about replacing the offending ballast.  Much
appreciated.

Dave