wiring change on observation rear light

Looks like it’s in series with the rest of the bulbs. Power up the whole board and measure the voltage across the rear light. It’s probably just a couple volts.

Hard to believe that a bulb would overload a transformer. What size transformer?

Here's how I add LED's to my strips, this is a RK observation car.  I just add the three LED's in series and then adjust a series resistor for the correct intensity.  These are lighting the two side markers on the roof as well as the rear facing taillight, see circled points.

I'd just replace the bulb with an LED, and I'd start with a 2K series resistor.  If that's too bright, increase the value, if not bright enough, decrease the value.  For a single LED, I usually end up with between 1500 and 2200 ohms.

GRJ, thanks for the help and diagram,  it looks like you have wired the white wire from the light to your strip, the black goes to where?  Where are the resistors added in?  What size bulb do you like?  thanks again Bert

The solder points on the strips come directly down the sides, so the positive side is on one edge and the negative side is on the other edge.  You can see the black wire going out of view on the top, the resistor is just out of view.

The resistor is a 1/8W or larger, it doesn't dissipate much power.  The LED and the resistor are wired in series, and it doesn't matter which leg the resistor is in, same effect anywhere in the circuit.  I use common 20ma LED's in a variety of styles and colors.  They're all generic stuff that I buy in quantity.

You can see on the strip the negative connections are on the top, the positive ones on the bottom.  I never noticed before that I didn't include quite enough of the car in the pictures to see the negative connection, it just goes to one of the solder points on the strip.

great, thanks for all your help.