Can anyone tell me what the square device is that spans the 2 leads of the light on this light board. The board is from the front light of an Atlas RS3 N Scale eng DC mode.
By the color, I would guess a surface mount Tantalum capacitor but I would not expect to see that type of cap there. I think I see the positive terminal indicator mark on it. I cannot pick out the data even when I blow up the photo.
If it is a capacitor, you should see the value and voltage.
Diodes and resistors are usually a black body.
If you have a decoder laying around you can see the different color devices and info.
Google the info on the item. I have done that a number of times with surface mount items.
Rich
An SMT cap…
Tom
Most SMT parts have one text and three digit number that normally will come up in a Google search.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
My Model Railroad
http://melvineperry.blogspot.com/
Bakersfield, California
I’m beginning to realize that aging is not for wimps.
Can you post a picture of the other side of the board?
If that’s from an N scale loco, then the two tabs on the right would be sandwiched in the frame, so that part, despite not looking like one, would have to be a resistor to keep the LED from blowing up as it would be connected directly to track power. A picture of the other side of the board will show if that device is wired in series or parallel with the LED.
–Randy
Get your Optivisor out and trace the circuit and an ohm meter. The meter should show you the device is a resistor.
Rich
OK here is the backside with the resister. I looked up picts of SMT Cap and they look exactly the same as the one on the board. There are no markings whatsoever on the item on the board i have.
Thanks for everyones input
Then that part on the other side is definitely a capacitor. Looking at the traces, the part on the other side is directly across (parallel) with the LED. Definitely a capacitor.
–Randy
What is the purpose of the capacitor on this DC light board?
Tom
normally a capacitor used in this way would provide some power during brief losses in connectivity with track voltage. The bigger the capacitor, the longer the time. A typical LED draw ~10ma.
Thank you everyone for your help
Tom
The capacitor probably absorbs reverse back emf spikes that would cause the LED in the opposite direction to flicker.
Mark.
I left the capacitor and resistor when I installed decoders in mine. Cut the traces at the two frame pickup pads to isolate the circuit. Then connect the blue and appropriate light wire to the circuit.