Re: ((OT)) Electronics (electrical) Problem

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

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.

----------------- TheSnoMan.com

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.

----------------- TheSnoMan.com

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.

----------------- TheSnoMan.com