I aquired three of these Atlas O constant light circuits off da bay. They were from early Atlas O extended vision cabooses. I would like to convert these to LEd operation if possible. IS there a different resister that is needed to do this? I think the bulbs are 1.5 v.
The positive leads goto the switch then to the circuit
While the returns goes to the shrinkwrap joint then back out to the common
Thanks in advance for your assistance in this matter.
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It looks to me like the resistors on the boards are for the IC (voltage regulator?). I think that is a Zener diode in there as well. I would be surprised if the output has any current limiting, so put a 470-ohm resistor in between the board and your LEDs and try it. Depending on how many LEDs you use, you may have to experiment with the resistor value.
I would recommned using 1000-1500 ohm resistor as a start. Then go higher or lower depending on brightness. You put the Resistor on one of the wires between the board and LED. Remember that LED stands for "Light Emitting Diode". A Diode is polarity sensitive. It allows voltage/current to flow one way - postive to negative, but not the other. So if the LED does not light, change the wires to the other LED.
Another point, if output from board is AC, the polarity will not matter.
I think the output must be DC, judging by the four diodes, which I assume form a bridge.
Can you read the markings on the red glass case diode and the 3-terminal component Q1? Knowing exactly what you have is another approach to coming up with a solution.
Can you put a voltmeter across the light bulbs when it is powered? If those really are 1.5 volt bulbs then no, this circuit will not light an LED, which would need a higher voltage plus a current limiting resistor.
Since you can light the LED with a resistor and a diode, is it really worth the effort to rescue this module? Ten cents worth of parts solves the problem.
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