((OT)) Electronics (electrical) Problem

I thought I knew this stuff, but there is a nuance that I'm not getting.

I have a fiber optic lighting system in my swimming pool. It takes a
24v/250A light bulb. The bubl does not light, but the filiment is okay. The
power supply (transformer) does not put out any voltage, so I bought a new
one.

The new transformer is stated to provide 40VA, but the light does not come
on. My guess is that a VA and a "regular" A are different. What's the
difference?

Jeff Strickland wrote:
> I thought I knew this stuff, but there is a nuance that I'm not
> getting.
> I have a fiber optic lighting system in my swimming pool. It takes a
> 24v/250A light bulb. The bubl does not light, but the filiment is
> okay. The power supply (transformer) does not put out any voltage, so
> I bought a new one.
>
> The new transformer is stated to provide 40VA, but the light does not
> come on. My guess is that a VA and a "regular" A are different.
> What's the difference?

VA is VoltAmps or Watts in DC current systems, a measure
of power output and most commonly used with backup power
supplies although it works on transformers.

250A is way too high for any bulb. 24V 250A is enough to run a
MIG welder.

It's time to start tracking. Start with the AC power to the
transformer and make sure it's working and the breaker hasn't
popped or the switch failed.

Then take an ohmmeter and measure the bulb side of that circuit
to make sure it's good and the bulb holder or wires haven't corroded.
(there could be a switch somewhere in that circuit also)

Hard to tell without looking at it myself.

--
DougW

On Tue, 29 May 2007 19:30:36 -0500, "DougW"
> wrote:

> take an ohmmeter and measure the bulb side of that circuit
>to make sure it's good and the bulb holder or wires haven't corroded.
>(there could be a switch somewhere in that circuit also)


This is good advise. Verify the circuit from transformer out. I also
agree that 250 amps is way too much. This would equal a little over
6000watts for bulb and as a comparision, aircraft landing lights on
big planes are 600 to 1000 watts and you see how bright they are. Also
to run a 250 amp bulb you would have to feed it with at least 2 ga
wire too and transformer would be so heavy that you would have trouble
lifting it to install it and it would take a 30 amp 230 volt circuit
to power it too.
-----------------
TheSnoMan.com

"DougW" > wrote in message
...
> Jeff Strickland wrote:
>> I thought I knew this stuff, but there is a nuance that I'm not
>> getting.
>> I have a fiber optic lighting system in my swimming pool. It takes a
>> 24v/250A light bulb. The bubl does not light, but the filiment is
>> okay. The power supply (transformer) does not put out any voltage, so
>> I bought a new one.
>>
>> The new transformer is stated to provide 40VA, but the light does not
>> come on. My guess is that a VA and a "regular" A are different.
>> What's the difference?
>
> VA is VoltAmps or Watts in DC current systems, a measure
> of power output and most commonly used with backup power
> supplies although it works on transformers.
>
> 250A is way too high for any bulb. 24V 250A is enough to run a
> MIG welder.
>
> It's time to start tracking. Start with the AC power to the
> transformer and make sure it's working and the breaker hasn't
> popped or the switch failed.
>
> Then take an ohmmeter and measure the bulb side of that circuit
> to make sure it's good and the bulb holder or wires haven't corroded.
> (there could be a switch somewhere in that circuit also)
>
> Hard to tell without looking at it myself.



NEW STUFF ...
I'm dumb.

The lamp has continuity at something like 1.5mohms, which is pretty close to
being open. I think I measure in at 1mohm.

I have several meters, the first one lied to me for whatever reason. My
Fluke 77 says I have 21vAC on the secondary of the original transformer and
the bulb is open until I get to the megohm range. (I think it might be the
20 megohm range to boot.)

"SnoMan" > wrote in message
...
> On Tue, 29 May 2007 19:30:36 -0500, "DougW"
> > wrote:
>
>> take an ohmmeter and measure the bulb side of that circuit
>>to make sure it's good and the bulb holder or wires haven't corroded.
>>(there could be a switch somewhere in that circuit also)
>
>
> This is good advise. Verify the circuit from transformer out. I also
> agree that 250 amps



OOPS!

Did I say 250 amps? It's 250 watts.

Jeff Strickland wrote:

> The lamp has continuity at something like 1.5mohms, which is pretty
> close to being open. I think I measure in at 1mohm.

That depends on the bulb and what temperature it's at.
Open is going to be infinite, but your basic 75W 120V blub
is about 60 Ohms cold. Halogen bulbs are a different aminal.

Just remember for any bulb it's best to keep your fingers off the
glass and use a clean cloth to handle them. Oil on the higher
output bulbs will cause them to fail early.

> I have several meters, the first one lied to me for whatever reason.
> My Fluke 77 says I have 21vAC on the secondary of the original
> transformer and the bulb is open until I get to the megohm range. (I
> think it might be the 20 megohm range to boot.)

I'd be thinking bulb or the wires leading to it.

--
DougW

"DougW" > wrote in message
...
> Jeff Strickland wrote:
>
>> The lamp has continuity at something like 1.5mohms, which is pretty
>> close to being open. I think I measure in at 1mohm.
>
> That depends on the bulb and what temperature it's at.
> Open is going to be infinite, but your basic 75W 120V blub
> is about 60 Ohms cold. Halogen bulbs are a different aminal.
>
> Just remember for any bulb it's best to keep your fingers off the
> glass and use a clean cloth to handle them. Oil on the higher
> output bulbs will cause them to fail early.
>
>> I have several meters, the first one lied to me for whatever reason.
>> My Fluke 77 says I have 21vAC on the secondary of the original
>> transformer and the bulb is open until I get to the megohm range. (I
>> think it might be the 20 megohm range to boot.)
>
> I'd be thinking bulb or the wires leading to it.
>


Thanks. I'm stuck on the bulb too.

My meter told me the bulb was good, but now I am not sure about the meter.
Maybe the meter is okay, but the moron working the buttons leaves a bit to
be desired. In any case, the bulb is dead, and the original power supply is
putting out voltage.

Jeff,

250A (A=Amps) is ALOT of current, so much so that it can't be correct. You
probably have no more than a 250A service for your entire house. I think you
mean W (Watts), which is usually how bubs are rated; by the Voltage and
Watts. The amps required, based on Ohms Law, is the Watts divided by the
voltage. The bulb you have is 250W divided by 24 Volts = 10.42 Amps.

Sounds like the power supply you bought only puts out about 1.666A at 24V
(24V X 1.66A = 40VA). So, the power supply is too small. You need one rated
at 10A plus a few more Amps for a margin of safety, so at 24V output the VA
is 24V X 10A = 240VA minimum.

Howard


"Jeff Strickland" > wrote in message
news:6R27i.2970$J76.2363@trndny03...
>I thought I knew this stuff, but there is a nuance that I'm not getting.
>
> I have a fiber optic lighting system in my swimming pool. It takes a
> 24v/250A light bulb. The bubl does not light, but the filiment is okay.
> The power supply (transformer) does not put out any voltage, so I bought a
> new one.
>
> The new transformer is stated to provide 40VA, but the light does not come
> on. My guess is that a VA and a "regular" A are different. What's the
> difference?
>
>
>
>
>
>
>

That's what I needed to know. the supply I bought is way too small.

And, the bulb is 250w not 250a. Sorry for that.




"doane_nut" > wrote in message
...
> Jeff,
>
> 250A (A=Amps) is ALOT of current, so much so that it can't be correct. You
> probably have no more than a 250A service for your entire house. I think
> you mean W (Watts), which is usually how bubs are rated; by the Voltage
> and Watts. The amps required, based on Ohms Law, is the Watts divided by
> the voltage. The bulb you have is 250W divided by 24 Volts = 10.42 Amps.
>
> Sounds like the power supply you bought only puts out about 1.666A at 24V
> (24V X 1.66A = 40VA). So, the power supply is too small. You need one
> rated at 10A plus a few more Amps for a margin of safety, so at 24V output
> the VA is 24V X 10A = 240VA minimum.
>
> Howard
>
>
> "Jeff Strickland" > wrote in message
> news:6R27i.2970$J76.2363@trndny03...
>>I thought I knew this stuff, but there is a nuance that I'm not getting.
>>
>> I have a fiber optic lighting system in my swimming pool. It takes a
>> 24v/250A light bulb. The bubl does not light, but the filiment is okay.
>> The power supply (transformer) does not put out any voltage, so I bought
>> a new one.
>>
>> The new transformer is stated to provide 40VA, but the light does not
>> come on. My guess is that a VA and a "regular" A are different. What's
>> the difference?
>>
>>
>>
>>
>>
>>
>>
>
>

The power rating given for small transformers is usually the max allowed
load for short periods and not for continuous operation at full load.
If you operate the lamp for long periods of time, you need (rough
estimation) a transformer capable of continuous power load of 250W / 0.8 ~=
310VA. Which depening of the quality of the transformer, means you might
need a 500VA transformer if you want it to last.

Bill Spiliotopoulos.

? "Jeff Strickland" > ?????? ??? ??????
news:6R27i.2970$J76.2363@trndny03...
>I thought I knew this stuff, but there is a nuance that I'm not getting.
>
> I have a fiber optic lighting system in my swimming pool. It takes a
> 24v/250A light bulb. The bubl does not light, but the filiment is okay.
> The power supply (transformer) does not put out any voltage, so I bought a
> new one.
>
> The new transformer is stated to provide 40VA, but the light does not come
> on. My guess is that a VA and a "regular" A are different. What's the
> difference?
>
>
>
>
>
>
>