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Light Board

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  • Member since
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  • From: Stratford, Ontario, Canada
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Light Board
Posted by tjerrard on Tuesday, November 14, 2017 2:24 PM

Light BoardCan 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.

 

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Posted by richg1998 on Tuesday, November 14, 2017 2:41 PM

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

N

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Posted by tstage on Tuesday, November 14, 2017 3:30 PM

An SMT cap...

Tom

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Posted by RR_Mel on Tuesday, November 14, 2017 4:20 PM

Most SMT parts have one text and three digit number that normally will come up in a Google search.
 
Mel
 
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Posted by rrinker on Tuesday, November 14, 2017 7:26 PM

 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

 


Modeling the Reading Railroad in the 1950's

 

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Posted by richg1998 on Tuesday, November 14, 2017 8:08 PM

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

Rich

N

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Posted by tjerrard on Wednesday, November 15, 2017 9:56 AM

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

backside

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Posted by rrinker on Wednesday, November 15, 2017 4:18 PM

 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

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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  • From: Stratford, Ontario, Canada
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Posted by tjerrard on Thursday, November 16, 2017 8:25 AM

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

Tom

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Posted by gregc on Thursday, November 16, 2017 8:47 AM

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.

greg - Philadelphia & Reading / Reading

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Posted by tjerrard on Thursday, November 16, 2017 8:49 AM

Thank you everyone for your help

Tom

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Posted by Mark R. on Thursday, November 16, 2017 8:56 PM

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

Mark.

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Posted by mfm37 on Saturday, November 18, 2017 4:57 PM
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.

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