Light Board

[tjerrard]

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.

 

[richg1998]

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

[tstage]

An SMT cap...

Tom

[RR_Mel]

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.

 

[rrinker]

 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

 

[richg1998]

Get your Optivisor out and trace the circuit and an ohm meter. The meter should show you the device is a resistor.

Rich

[tjerrard]

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

[rrinker]

 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

 

[tjerrard]

What is the purpose of the capacitor on this DC light board?

Tom

[gregc]

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.

[tjerrard]

Thank you everyone for your help

Tom

[Mark R.]

The capacitor probably absorbs reverse back emf spikes that would cause the LED in the opposite direction to flicker.

Mark.

[mfm37]

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.