Insulating Tight Fit Areas Against Shorts

Model Railroader Electronics and DCC
1

I want to replace some incandescent light bulbs with LEDs on some old Model Power block signals.

I plan to use some Miniatronics 3mm bipolar LEDs with 2 legs.

In order to get the small wires soldered to the legs and still fit inside the mast, I cannot protect the soldered points with heat shrink tubing.

Is there something like insulated paint that can be used to protect the soldered connections from shorting out and destroying the LEDs ?

Rich

2

Rich,

I’m not familiar with the Model Power signals, but if the mast is brass,can You solder one of the legs to it and have one wire with heat shrink tubing in it??

Frank

3

Frank,

The diameter of the brass mast is pretty small. There are wires already running through the mast. My plan is to cut off the incanescent bulbs from the wires and re-use the wires to connect them to the legs of the LED. My only concern is the soldered connection points which will be nearly touching as the wires protrude out of the mast right behind the brass signal head.

Rich

4

Kapton tape is thinner than regualr electrical tape, you might be able to get a sliver in there. ANd it’s fairly puncture-proof. ANother option would be laying on a coat of nail enamel, both ont he inside of the mast and on the soldered connections. Nail polish is thicker than regular paint, and should hold up once assembled because there should be little if any movement.

–Randy

5

Rich,

How about 2mm LEDS ??

Frank

6

Thanks, Randy.

I am not sure that Kapton tape would work under these conditions but the nail polish is an idea worth trying.

What do manufacurers of signals use in this situation? They seem to use some type of resistance paint, black or silver in color.

Rich

7

Rich.

Any marine supply shop would have a product called liquid electrical tape. It comes in a can with a brush attached to the top.

Pete

8

Rich,

I didn’t think of it at the time, but Randy’s comment sounds like a visible one.

Frank

9

ahhh, interesting. I will check it out.

Thanks, Pete

Rich

10

I’ve got a can of that liquid insulation, which I bought for my own signal bridge project. It works very well for that application. It goes on and dries flat black. It stinks when you put it on, but the smell dissipates and, well, I’m still here so it can’t be too bad.

11

I see that Lowes sells it, a product called Liquid Tape.

Home Depot carries it too.

Rich

12

If you’re referring to these types of Model Power signals – Nr. 1684:

http://www.modelpower.com/searchresults.asp?cat=196

I’ve converted over 20 of the two bulb versions to 3mm LEDs.

I removed the existing bulbs, which is sometimes very difficult to do because of the black goop they use to install and insulate the wiring. I pulled enough wire out to which I could solder, soldered very close to the 3mm LED base with a controlled-temperature soldering station with a very fine tip, cut off the remaining LED wire, and then used silicon goop to hold the LEDs in place. The wires on the back of an LED are stiff enough to keep them from touching each other if you solder as close to the base as you possibly can.

No further insulation was necessary. At the same time I reversed the colors so green is on top and red on the bottom. Model Power wires them backwards to railroad standards.

You can see some of them on our HO scale club layout at http://cwmrrc.com

13

Yep, those are the ones. I have four of the #1682 signals. The bulbs and the attached wires move around pretty easily, so I will have no problems in that regard. As you noted, the close up soldering will be a little challenging.

The two incandescent bulbs provided by Model Power, a red and a grren bulb, look ridiculous - - - too big and too bright. I didn’t know any better when I bought them 9 years ago after first entering the HO scale side of the hobby.

Rich