Where exactly do you check for polarity at the ballast connections??

[netvoy]

I have read the faq and find myself with the predicament that I too
want to figure out if a ballast is good. It is obviously not a good
idea to test it live as per the thread where I captured the information
below. If I interpret the information I've read so far at startup the
277(two different 120v circuits power several four bulb setup in this
kitchen) volts rated ballast I have is capable of putting out up to
600v and since the wires are dangling during the test and without a
load it is likely that the rated voltage will not dissapear of them
wires; the load in this case two flourescent bulbs (48 inch in my
case). Yet this voltage endangers me and if I were to measure; it is
likely useless unless loaded.
I digress. My intention is to understand what the post below refers
to as polarity. I have a pair of red, a pair of blue, a pair of yellow
and the black and white wires. Is polarity an issue at all three
pairs? Is it an issue at the red and blue pairs? The wiring schematic
at the ballast is not very clear on the particular label of a + or -
connection.
Is the yellow pair considered a filament just as the red and blue
pairs?
If a ballast goes bad will the second automatically be damaged or
likely damaged?
Thank you very much for any additional info....
=================================================================

[email protected] said the following to All on the subject of
How-to Test Fluorescent Ballast (24 Sep 97 17:12:35)

bc> I have checked the FAQ and have searched the WEB, but I have not
found
bc> any information on how to test if a fluorescent light ballast is
any
bc> good. I will be helping to re-lamp my daughter's gymnastics club
in the
bc> near future and I would like to test the ballasts that seem
bc> questionable. These are standard four-foot, two lamp fixtures that
are
bc> row mounted. I have installed new fluorescents many times, but I
am not
bc> familiar with the internal operation of a ballast. Any help that
you
bc> can provide regarding ballast operation and test would be
appreciative.
bc> I have a multi-meter, but is there any (low cost) specialised test
unit
bc> or methods that might be necessary.


A ballast is a simple transformer with a very high impedance secondary
winding which makes its current self-limiting. It also has windings for

each lamp filaments. At startup the filaments get most of the power and

heat up to facilitate ionization.

Meanwhile the secondary builds up a very high EMF which finally fully
ionizes the plasma between both filaments. At this point the effective
resistance of the conducting plasma is quite low and the current flow
is
limited by the secondary's impedance. This also partially saturates the

core and as consequence reduces power to the filaments.

The usual failure in ballasts is that the secondary's insulation
deteriorates and it starts leaking to ground. Often because the proper
wiring polarity was not observed. The secondary can thus no longer
generate the high EMF required to start the plasma conducting.

The KISS test method is to use a known good lamp. If it lights, the
ballast is good too. The ballast can also be tested with the power off
by
checking for continuity in the filament windings and a very high
resistance to ground for each filament. Don't try this with power on!

 

[Sam Goldwasser]

Easiest and most reliable way if you're testing many ballasts is to simply
set up a fixture with known good lamps, wiring, sockets, etc., with quick
connect terminals of some kind for the ballast wires.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[Michael Ware]

I have read the faq and find myself with the predicament that I too
want to figure out if a ballast is good. It is obviously not a good
idea to test it live as per the thread where I captured the information
below. If I interpret the information I've read so far at startup the
277(two different 120v circuits power several four bulb setup in this
kitchen) volts rated ballast I have is capable of putting out up to
600v and since the wires are dangling during the test and without a
load it is likely that the rated voltage will not dissapear of them
wires; the load in this case two flourescent bulbs (48 inch in my
case). Yet this voltage endangers me and if I were to measure; it is
likely useless unless loaded.
I digress. My intention is to understand what the post below refers
to as polarity. I have a pair of red, a pair of blue, a pair of yellow
and the black and white wires. Is polarity an issue at all three
pairs? Is it an issue at the red and blue pairs? The wiring schematic
at the ballast is not very clear on the particular label of a + or -
connection.
Is the yellow pair considered a filament just as the red and blue
pairs?
If a ballast goes bad will the second automatically be damaged or
likely damaged?
Thank you very much for any additional info....

| Return Address: [email protected]
First, the polarity. I think what they meant was just wiring it properly,
per the instructions or diagram. Each wire of the same color (red, blue,
yellow) should be interchangeable. There is no + or - here, it is all AC
current. While the voltage output is somewhat high (600v) the current for a
48" lamp is around 800mA.
If you know the particulars of the ballsast (manufacturer and model) it is
likely that you can look up wiring diagrams on the internet.

 

[Just Another Theremin Fan]

There is no + or - here, it is all AC current.

Anyone who needs telling this should not be encouraged
to play with electrical fittings. The twat could kill someone.

 

[James Sweet]

| Return Address: [email protected]


First, the polarity. I think what they meant was just wiring it properly,
per the instructions or diagram. Each wire of the same color (red, blue,
yellow) should be interchangeable. There is no + or - here, it is all AC
current. While the voltage output is somewhat high (600v) the current for a
48" lamp is around 800mA.
If you know the particulars of the ballsast (manufacturer and model) it is
likely that you can look up wiring diagrams on the internet.

High output lamps are 800mA, standard lamps (in north America anyway),
standard T12 lamps are 430mA, T8 lamps are 230mA. At 600V, the output is
dangerous, it only takes about 200mA to kill you. As you say, the two
reds, blues, or yellows are interchangeable and it's AC so there's no
polarity.

 

[Sam Goldwasser]

High output lamps are 800mA, standard lamps (in north America anyway),
standard T12 lamps are 430mA, T8 lamps are 230mA. At 600V, the output
is dangerous, it only takes about 200mA to kill you. As you say, the
two reds, blues, or yellows are interchangeable and it's AC so there's
no polarity.

Yes, but the 600 V won't be capable of anywhere near 200 mA. Not to say
it isn't dangerous, but not quite as instantly deadly.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[James Sweet]

Yes, but the 600 V won't be capable of anywhere near 200 mA. Not to say
it isn't dangerous, but not quite as instantly deadly.

Of course, but it's worth mentioning for the novice, wouldn't want them
to get the idea that it's completely safe to go touching those wires.
I've been bit by the output of a ballast before and it wasn't fun, if
I'd been standing on a ladder or something it could have caused quite an
injury.

 

[netvoy]

Easiest and most reliable way if you're testing many ballasts is to simply
set up a fixture with known good lamps, wiring, sockets, etc., with quick
connect terminals of some kind for the ballast wires.

It probably would not be practical in my situation for I have many
types of ballast and fluorescent combinations in this 10 story (800+
rooms) building. The type of ballast at any given time will be
different. I was hoping they were all designed similarly and to be
tested electronically somehow easily. Mind you, if management found
out that I was spending time on setting up something that ideally would
save on costs around here they likely fire me for wasting time. Yes,
they are that limited here.

 

[netvoy]

Allow me a couple of further questions: Voltage output is 600v only
at startup correct?
What would be a non-self-limiting secondary? The ballast is from the
Advance Transformer Co. a 277/60hz/Class P unit. A Mark III Kool Koil
High Power Factor Series Ballast specifying at 35w rs lamps 460 Ma
Max???!!! I'll definately keep looking for a schematic on the web.
Thanks

 

[netvoy]

And I guess we can assume based on your post that all fluorescent
bulbs run with AC, that the schematic is included for clarity in all
ballasts, that someone should self-limit himself from asking questions
that clarify issues such as polarity when it is not clear to them
whether they exist to begin with (which begs the question: does
polarity exist in AC systems?). Are you creating impedance toward
progress sir? Are you not creating enough EMF within your brain cells
to push into clarity that the light bulb took a 2 person team effort
over a thousant tries to make it work. Yet in a SHORT(aka - a leak to
ground) response you deny a friendly poster the right to question and
search for the clarity a two year old deserves?

Oh well I am all wound up; my filaments must be overloaded;
resistance is futile .

If I wire the ballast direct to AC will the 600v AC be present
without the load? If so where can it be measured at? Is it between the
flourescent endpoints of the bulb or within each corresponding color
pair?

 

[Sam Goldwasser]

Allow me a couple of further questions: Voltage output is 600v only
at startup correct?
What would be a non-self-limiting secondary? The ballast is from the
Advance Transformer Co. a 277/60hz/Class P unit. A Mark III Kool Koil
High Power Factor Series Ballast specifying at 35w rs lamps 460 Ma
Max???!!! I'll definately keep looking for a schematic on the web.
Thanks

I'm not sure at this point what you are trying to do. If you have a fixture
that doesn't now work but used to and has power to it, and installing new
lamps doesn't help, then by process of elimination, the most likely cause
is a bad ballast.

If you have a bunch of ballasts sitting in a box that you wan to test, it's
still probably easiest to just wire each one up to a dummy fixture and check
it under real life conditions.

Else, you could measure voltages or resistances comparing a known good
ballast of the same model to the suspect ones.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[James Sweet]

Allow me a couple of further questions: Voltage output is 600v only
at startup correct?
What would be a non-self-limiting secondary? The ballast is from the
Advance Transformer Co. a 277/60hz/Class P unit. A Mark III Kool Koil
High Power Factor Series Ballast specifying at 35w rs lamps 460 Ma
Max???!!! I'll definately keep looking for a schematic on the web.
Thanks

Magnetic rapid start ballasts are pretty simple, aside from the power
factor correction capacitor on the primary, a ballast is nothing but an
inductively leaky transformer with the secondary tapped at each end to
provide voltage to heat the cathode filaments in the tubes and a
separate tap for the middle set of cathodes (both lamps are wired in
series.) They rarely fail and when they do it's usually fairly obvious
as they tend to run real hot and scorch the label or drip tar until the
internal thermal fuse blows. A quick check I suppose would be to measure
the voltage between one of the blue wires and one of the red wires, you
should get several hundred volts. Then measure between the two reds,
between the two blues, and between the two yellows, each of those pairs
should have just a few volts. An even quicker check is to have a set of
known good lamps and pop them into each fixture in question.

 

[netvoy]

I'm not sure at this point what you are trying to do. If you have a fixture
that doesn't now work but used to and has power to it, and installing new
lamps doesn't help, then by process of elimination, the most likely cause
is a bad ballast.

Basically, I am trying to understand operation and test procedures
for the ballast as is without adding anything extra components no
bulbs, no end hookups ; I wanted to picture precisely the how it works
with the simplest setup (in this case just tie it up to power line and
use the multimeter to figure out if it is good. It is apparently a bit
more complex than that. My company's philosophy is to ruthlessly
minimize expenses --does not matter if it is a savings in the long run
-- yes we know better. So they are unwilling to buy extra anything and
it is not a financial priority expense on my part ( actually more like
financially unsound for me to invest in any parts due to personal debt
). If i can offer them the knowledge that I can do for them but this
is primarily for me; I like to know how things work.

If you have a bunch of ballasts sitting in a box that you wan to test, it's
still probably easiest to just wire each one up to a dummy fixture and check
it under real life conditions.

It is unlikely that I will have flourescents, or any other parts to
test the ballast no matter how smart of an idea this is; as the budget
allowed to us does not even cover half the bulbs we replace in this
building per month. We are always short a couple of boxes.

Else, you could measure voltages or resistances comparing a known good
ballast of the same model to the suspect ones.

This is basically what I needed to get to. Obviously a complex
situation for every ballast is a bit different. And yet up to this
point not clear what voltage value for my given chosen test point, mind
you, it likely changes value once the flourescent bulb is fully warmed
up.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/

Thank you very much for the info.....

 

[netvoy]

This is very valuable info. I now understand all practical issues
with the repair of the unit at hand at least I believe that. In my
particular situation we have a misapplication error; the bulb does not
match the ballast. It is a two ballast four bulb install; you can bet
that we have no replacement parts. One of the ballast has an almost
invisible leak and is darkened. Somehow I was expecting at least one
to work.

To conclude :
1) Voltage values at ballast check points are probably irrelevant
since you have to see the unit in operation to know it is good; the
presence of the proper value only tells you that the ballast is likely
to be good(ok to save it for further actual use testing). If it is
good; it must match the bulb in question.

Only one more doubt : once the bulb is fully warmed up do the voltage
values change
at the test points?

Tkx for all info....

 

[James Sweet]

Only one more doubt : once the bulb is fully warmed up do the voltage
values change
at the test points?

Yes, the voltage values change as the lamp warms up, as well as from one
lamp to another depending on age and manufacturing tolerances. The
voltage is not a function of the ballast though, but of the lamp itself,
which having a negative resistance curve will settle at whatever voltage
it "likes" at the current the ballast is pushing through it. A ballast
is a constant-current source whos voltage output will vary depending on
the load, unlike the constant-voltage source you get from a wall outlet
where the current varies depending on the resistance of the load. The
purpose of the ballast is to convert one to the other and due to its
very nature it can only be tested accurately while connected to a
suitable load.