NCE SB3 and 3156 Bulb

[karle]

The NCE SB3 manual recommends a 1156 light bulb be wired in series with the SB3 output to limit current in case of a short.   Another website said a 3156 bulb can be used in place of a 1156 bulb and is easier to wire because you can pull off the base and easily connect to the bulb wires.  Has anyone tried this?  I did and it doesn't appear to work, i.e. when doing the "quarter test" the SB3 trips instead of the bulb lighting up. The only thing I can figure is I used a Phillips 3156 Long Life bulb.  Maybe a standard life buld should be used instead?  Any ideas?  On my previous layout I used an 1156 with the SB3 and it worked.  The 3156 makes the wiring simpler by avoiding the need for a buld socket.   

[RR_Mel]

I use the 3156 bulb for load testing on my bench.  I soldered some connectors to the bulb pins.  I did the same on a 3157 dual filament bulb, the break side draws 2 amps at 12 volts and the taillight side draws .6 amps, very handy bench test loads.

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[rrinker]

 1156 and 3156 seem to be identical in relation to current, which should be far enough under the SB3's output to allow it to light up without tripping. The SB3 is capable of 3 amps, so it should light a 2.1 amsp bulb with no problem. Do you have other stuff on the rails at the same time you are doing the quarter test?

                               --Randy

[richhotrain]

karle

The only thing I can figure is I used a Phillips 3156 Long Life bulb.  Maybe a standard life buld should be used instead?  

The standard 3156 bulb and the long life 3156 bulb are both 2.1 amps.

Rich

[gregc]

karle

The only thing I can figure is I used a Phillips 3156 Long Life bulb.

the resistance and hence current of an incandescent lamp is only stable at it's operating temperature.  The initial current through an incandescent lamp is higher than it's rated value.   As the filament heats up, it's resistance increases and the current decreases.

the heating characteristics of the long life 3156 may initially allow a higher current to pass and long enough for the short protection in the SB3 to kick in.

it may be worth trying an 1156 bulb or standard 3156 as you suggest.

[karle]

Thanks all for the replies. Yes I had a locomotive on the track in the block where I ran the quarter test (actually used a steel ruler for the test). Would that loco make a difference? This weekend I”ll see if I can find a “regular” 3156 locally and report back the results.