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tstage wrote:Anyone ever have a transformer go bad on them? I have a 3-month old Miniatronics 1.5VDC "wall-wart" transformer (that I use to run the exterior lighting on my layout) that is acting strange. The lights initially power up full but immediately reduce to about 1/2 power. Over a matter of a several minutes the lights get dimmer and dimmer till they are barely glowing. The outside of the transformer feels fairly warm to the touch but not hot. It just started tonight so I really haven't had a chance to test it out fully. Does this sound like a no-brainer problem with the transformer itself? Thanks.Tom
Since your wall wart puts out DC (instead of AC); it is more than a transformer. It will have a few other components (capacitor, diodes, resistors, etc.); any of which could go bad. Without knowing your load (in amps) and if the load actually changed (increased) due to some layout malfunction; it is not possible to really tell where the problem lies. I would bet on a bad wall wart though.
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Tom, what is its current rating and how many lights do you have attached to it ? It does sound like an over current condition. If it has over current protection, it may not be toast. You might try hooking just a few lights to it to see if will output the proper voltage and light the lamps to the proper brightness. I think I recall you using 60ma lamps. If so, just remember that 16 bulbs equals 1A. Also the other thing is that with 1.5V you have to be extra careful about voltage drops. Far more so than 12V or higher. Its the same reason that neighborhood electrical distribution legs run at 14,000 volts and higher and not 220V.
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tstage wrote:Thanks everyone. I really appreciate each one of your comments and inquiries.To answer your questions:Just to update everyone. After I read everyone's comments, I went back downstairs to count the number of lights I had drawing off the transformer. As I stated above, the count came to a total of 12 - well within the limits. Just for fun, I plugged the transformer back into the electrical strip and - low and behold - the bulbs light up at full power now, with no overheating or dimming.I'll double-check it again and leave them on for a little while to see if the problem reoccurs. I did nothing at all to them between now and the time I posted the original thread.I'll keep you posted. Thanks again for the feedback. Tom
IF everything continues to work; you have one or two possibilities for the problem (three, if something is really defective).
1) You could have a high resistance connection where the power supply plugs in to the outlet (corrosion or poor joint - possibly to the actual outlet connections from the feed wire).
2) Some intermittent high resistance short in your lamp wires or supply wires to the lamps. Something on the load side trying to draw way too much current from the supply.
You might have "corrected" either of these problems by jiggling things while you were checking everything out. I sure would try my best to cause the problem to show up; so that it can be fixed once and for all (I am sure that your homeowners fire protection clause will rest easier if you can find out what caused your original problem).
Tom, I was able to see from the label that it is a 1.5A supply, so yes, you are well within the limits. The voltage drop sounds fine too. My only point was that a .1V drop at 1.5V is a 6% drop whereas at 12V it is less than 1%. With the low amount of current and short distances you should be fine.
Alan_B wrote: IF everything continues to work; you have one or two possibilities for the problem (three, if something is really defective). 1) You could have a high resistance connection where the power supply plugs in to the outlet (corrosion or poor joint - possibly to the actual outlet connections from the feed wire). 2) Some intermittent high resistance short in your lamp wires or supply wires to the lamps. Something on the load side trying to draw way too much current from the supply. You might have "corrected" either of these problems by jiggling things while you were checking everything out. I sure would try my best to cause the problem to show up; so that it can be fixed once and for all (I am sure that your homeowners fire protection clause will rest easier if you can find out what caused your original problem).
Alan,
tstage wrote: Alan, I had a couple of exposed (uninsulated) soldered wire joints underneath the table that I'm wondering whether or not they were touching one another somehow. That might cause an electrical "ruckus" to the transformer, wouldn't it?Tom
I had a couple of exposed (uninsulated) soldered wire joints underneath the table that I'm wondering whether or not they were touching one another somehow. That might cause an electrical "ruckus" to the transformer, wouldn't it?Tom
Absolutely.
One problem with these wall transformers is that they lack a circuit protection indicator. They are a good source for inexpensive power.
Jim
Jim,
Minitronics also makes a 1.7 mm 1.5 volt 30 ma lamp with a 5000 hr rating they come 10 in a pack. LHS has/had them (bought them all). They were more expensive though about $12. I don't have the part number on me at the moment but it's close to the 1.2mm number.
I use Miniatronics 14v bulbs with a 16,000hr life rating. I am hoping to never have to change them.