LED signals

I have amassed a fair collection of colour light signals, sadly most of them don't work because one or both of the bulbs have fused.

Although spare bulbs are readily available, the new layout is being constructed with public exhibition in mind, that means that the signals could be lit for up to or in excess of eight hours at a time. Filament bulbs generate heat and heat discolours the lamps. Of the working signals I have, the colours are pretty poor and they have a tendancy to illuimate half the layout.

The other issue is that I'd like to use my signal matrix control that I bought years ago but could never use as it can't handle the current consumption of filament bulbs.

Having looked at the back of the signals and the method used by HD to install the bulbs, I worked out a way to fit LEDs instead.

This is in no way intended as a "how to" guide, more of a "how I did..."

Heat-shrink tubing, a hot soldering iron and the ability to solder quickly are must haves.

So, I started with a signal with only one functioning bulb...

The light from this is almost yellow in appearance.

The ladder unclips from the body of the signal and pulls away, the wiring that is just tucked into the body can be eased out.

One screw secures the back of the lampholders to the signal...

I also need to make a modification to the wiring in the base. I'll be fitting the ballast resistor between the body of the signal and the common connection.

The 3.5mm LEDs and ballast resistor, only one resistor is required and can be wired either side of the LED.

My signal controller uses permanent live and switched neutral wiring, so the polarity of the LEDs has to be reversed, the common feed is live.

The long tails of the LED are bent down into the signal body, handily the ladder fixing tends to scrape away some of the white paintwork. If it doesn't then a small section can be scraped away. The ladder will hide it!

Then the two legs are soldered into the body...

Heat shrink tubing is a must to insulate the LED connections properly. The existing wires are soldered to their corresponding LED, the heatshrink is then slid right up to the LED and heated with the soldering iron...

The shielded legs are also bent into position and the wires tucked back into the signal body.

The ladder holds all of this in place, the soldered LED bulbs don't appear to need further fixings to keep them in place, the legs are stiff enough to keep them in-situ.

I unscrewed and removed the "earthing" tab that connects the signal body to the "C" connection. This is then cut and the resistor is soldered between the two connections. This is where quick work with a hot iron is essential as the base is plastic...

Time to test...

Cheap and easy mod. Takes about 20 minutes and as the original lampholders have been retained, this could be reverted back to bulbs if needed (which I won't)