((OT)) Electronics (electrical) Problem

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.

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.

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

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

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...

Two thing, a 40VA replacement transformer is not going to power a 250 watt bulb. Next, a 250 watt 24 volt bulb is going to read about a dead short on ohm test (much less than 1 ohm) While it will look like about a 1.5 ohm load when hot, resistance decreases when element is cold so do not be surprized if it look like or near a dead short on a 1x scale. BTW, a 24volt 250 watt bulb is a pretty serious bulb and can get pretty warm.

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Just another thought for you.

I decided to fix the pool lights at my brother in laws cottage 'way' up north and talked to a pool tech before going.

He stated the power transformers were the weak point.

This fiber unit used a 12 V 75W 'pot light' and a colored spinning wheel but supposedly could take a 100W.

Sure enough, I didn't even need to meter the power supply once I saw the melted solder on the output transistors. A new unit was pricey and I 'really' don't like replacing 'weak points' with 'new' weak points.

So I went into the local town to the hardware store, picked up a 120V

50W bulb (the biggest they had, no 75's), went across the street to a Radio Shack and found a couple pigtails that fit the bulb's base because no one had the proper pigtail in town and converted the sucker to a 'line voltage' box.

Basically I tossed out the 12 volt crap and just went 120V. It works great and some day when I go back up if I get ambitious I will up the bulb to a 75W or even the 100W the 'fixture' says it can handle. There is a colored wheel to avoid melting.

The owners are fine with the lower 50W though so.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

After all this back-and-forth about the problem, all I can add is that Jeff ought to not throw good money after bad, or incur further risk to himself by calling in a really good electrician (not the guy who can replace a wall switch) and leave it to him. We all think we know a little about electricity, and it's just enough to get a surprise in the form of a lethal or nearly lethal shock. I'd just as soon not read the news and find that Jeff Strickland was found face down with two wires in his hands. ....."let's see now, was that 250 Amps or 250 Watts???" Stick to plumbing repairs. Lots of professional electricians have succumbed to electrical shock, but I've yet to hear of a plumber drowning.

A nearly lethal shock will give you years and years of health problems, as any survivor of being struck by lightning can tell you.

I have a garage that was wired without a single junction box, except where required for switches and receptacles. The cables are just spliced together in the middle of the air. A piece of extension cord material was used to feed one room. It was of course wire nutted into a piece of romex and then sealed into a wall. I lost no time in telling the seller of the property and the guy who wired the garage that both were morons.

Either get a real electrician or a Time/Life diy book.

There is an electric pipe thawer that could give you quite a jolt. I see a lot of burned fingers from sweating copper tubing together.

Saludos cordiales,

Earle

The diy book might be safer, a good friend recently retired from his job as a building inspector, he was a journeyman electrician by trade before becoming an inspector so he knew the electrical code very well.

He said it was almost unbelievable the number of jobs done by experienced, licensed, electrical contractors and/or electricians that had to be ripped out and done over because of numerous code violations and unsafe wiring done intentionally to save a buck.

You'd think it would be cheaper to wire a building correctly than to tear it all out and do it over but the contractors lived with the constant hope they wouldn't get caught... :-(

Well as a plumber that works under pools, I have gotten pretty wet....

Then there are the houses that use the cold water pipe as the main ground for the electrical panel for the house.

Man oh man the blue fire that happens if you happen to cut that SOB with a 240V dryer or stove or even just the 120V stuff turned on anywhere in the house is Wicked! Just turns the pipe cutter into instant slag.

I make 'real' sure where the electrical panel is when I cut a cold line and half the time put a set of booster cables across where I want to cut if in any doubt.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

Listen, first of all, you are not stupid just because you do not know something, that is why you ask questions. Stupid is not even asking the question. Some multimeters can be a bit confusing but generallt you use one set of lead connections for volt and ohms and another for AMP if your meter supports that (those terminals have a shunt accross them internally for current measurements) You always what to use 1K range on ohm meter when checking light bulbs. Also transformers generally rarely fail and when they do there is usually little doubt because they will appear or smell burnt. Only a few things can kill a transformer. The first is overloading it and it overheats and insulation in winding break down and it shorts out internally. The second is that a winding open up internall which is really rare in a power transformer and the third it insulation break down from time and heat which cause it to short internally. Properly sized for load a power transfomer can live many many years.

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I built an o-scope (Heathkit). :) It still works even though it's now been replaced by a Tektronix unit with a few more features.

Still remember adjusting the deflection voltage +50, -50 and noticing one of the FETs was a bent over a bit.. so like a dumbass I grabbed it to straighten it out and it straighten me out.

Not like I was just measuring the damn thing.

noooooooooooooooooooooo

Doug, in reference to your link, there was a "revbeergoggles" over on the Venture Motorcycle group I used to be a member of. Same guy? Spdloader

nope.

Got that moniker over in alt.slack

It's a good one. He was a great guy from what I remember.

Later, Spdloader

I understand that but what limits the transformers operational temp limit is the nature of its winding insulation. Most transformer suitable for outside usage have moisture resist insulation and can take a pretty serious amount of heat for a lot of years. ALso, sine this it a low voltage output transformer it is even less prone to fail from age if properly sized because of less demand on insulation and the wall voltage insulation is well prtectec because it is the first winding placed on the core. I actually wound a few transformers many years ago for some hobby builds to get the desired voltage from them. They operate on a very simple theory and are extremely relaible. Like I said when one goes south you will know it by its appearance or odor generally.

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