Upper Subway Marker Lights

If this is like several of the subways I ran across a couple years ago, they wired the rear red LED's and the front green LED's in parallel with no equalizing resistors.  That results in most of the time the rear red ones work and the green one's don't.

The solution is to add a 100 ohm resistor in series with the red LED wire to allow the green ones to get enough voltage to light.

@gunrunnerjohn posted:

If this is like several of the subways I ran across a couple years ago, they wired the rear red LED's and the front green LED's in parallel with no equalizing resistors.  That results in most of the time the rear red ones work and the green one's don't.

The solution is to add a 100 ohm resistor in series with the red LED wire to allow the green ones to get enough voltage to light.

John, there’s no LED’s in this set, it’s all glass bulbs running off of track power from the roller. The wire from the marker light is going to pin 3 of the 12 pin socket.  

The marker makes sense then, they programmed the interior lights for markers to drive the bulbs, typically the markers are LED and come off the 8-pin connector.

Well nothing lite up on that?  Do the couplers work?  You may have lost PV.  G

@GGG posted:

Well nothing lite up on that?  Do the couplers work?  You may have lost PV.  G

It only has one front coupler that does work. Checking the board, pin three for power, how many volts should be there, and would it be AC or DC? Thx

The purple wire provides Positive voltage referenced to DC ground.  Normally about 22VDC when track power at 18VAC.  The returns go to negative ground and are PWM via fets.  So the effective voltage for lights is 6V.

If all the lights out that is most likely PV loss.  This model uses 2 pin molex connectors correct?  Not spring pads to get power to the light?  Can have cold joint under the heat shrink. Or broken wire.  Unless all bulbs burned out.  G

@GGG posted:

The purple wire provides Positive voltage referenced to DC ground.  Normally about 22VDC when track power at 18VAC.  

GGG, thanks for the reply. I have an MTH Z750 hooked up to the test track. Full power on it to the tracks is 17.74 VAC, the headlight circuit is giving me 25.73 VDC.  

Let's be clear, that is not the circuit though, that is just PV.  If you measure the voltage at the 2 pin plug for a light bulb what voltage do you get?  Should be about 6V.   G

@GGG posted:

If you measure the voltage at the 2 pin plug for a light bulb what voltage do you get?  Should be about 6V.   G

25.73 is what I got at the headlight make plug

So you got 25V measuring between the 2 pins?  If so the FET is shorted and your getting full voltage and blew the bulbs.  Do any lights work on this?  G

@GGG posted:

Do any lights work on this?  G

yes sir, the head an tail lights work as they should flipping back and forth with direction. The marker lights are good also, if I plug them in the head or tail light plug. But I get no power out of the marker light plug.

Well if the bulbs are good, you do not have a shorted fet that would burn them out.  So I am not sure how you are reading a voltage at the connector and the bulb won't work, but does work in another plug?  So maybe the board is damaged and no actual output to the plug.  Or sound file wrong with out the light signal.  Hard to go further here with out the product.  But if the bulb is really good.  You do not have actual 6V effective at the plug 2 connectors.  Measuring purple to DC ground is not effective, you need to have the ground back through the fet to have the effective voltage at the connector.  G

@GGG posted:

So I am not sure how you are reading a voltage at the connector and the bulb won't work,

sorry for the delay GGG, I did t notice it. I do not get power from the board for the marker light. But I know the bulbs are good because they light when I swap the plug with the head lights.

Usually light fet can be repaired on the board. G

@GGG posted:

Usually light fet can be repaired on the board. G

Can you recommend someone that can fix the fet?

I can, my email in profile send me one.  G

Life is good, thanks GGG

Brian NY

You are welcome. G