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I have this engine and I'm converting the headlight to an LED. There's a plug that is attached to the headlight. On one end of the plug, there are a brown and a black wire, I've attached the red wire to the brown and the black to the black. Problem is I'm not getting any light when connected that way. Connecting just the LED to power, it works fine. Any ideas? 

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Trainlover9943 posted:

I have this engine and I'm converting the headlight to an LED. There's a plug that is attached to the headlight. On one end of the plug, there are a brown and a black wire, I've attached the red wire to the brown and the black to the black. Problem is I'm not getting any light when connected that way. Connecting just the LED to power, it works fine. Any ideas? 

Flip it around. LED's only work one way. Maybe it's wrong?

Sid's Trains posted:
Trainlover9943 posted:

I have this engine and I'm converting the headlight to an LED. There's a plug that is attached to the headlight. On one end of the plug, there are a brown and a black wire, I've attached the red wire to the brown and the black to the black. Problem is I'm not getting any light when connected that way. Connecting just the LED to power, it works fine. Any ideas? 

Flip it around. LED's only work one way. Maybe it's wrong?

No change. 

Trainlover9943 posted:
Sid's Trains posted:
Trainlover9943 posted:

I have this engine and I'm converting the headlight to an LED. There's a plug that is attached to the headlight. On one end of the plug, there are a brown and a black wire, I've attached the red wire to the brown and the black to the black. Problem is I'm not getting any light when connected that way. Connecting just the LED to power, it works fine. Any ideas? 

Flip it around. LED's only work one way. Maybe it's wrong?

No change. 

Is there any power actually going to those wires?

Sid's Trains posted:
Trainlover9943 posted:

No voltage on the leads. 

Well that's your problem. Try turning the headlight on with the Tmcc remote. If that doesn't work then there is either a disconnected wire or a bad board. Trace the leads back to the board and test the right at the board.

I've tried using Aux2 and got nowhere. I'll look at the board. I feel like the plug is bad. 

Just a thought here. An LED is a diode, a one way device. In know for a fact from a Lionel C420 experience, that certain R2LC receivers on the light outputs and maybe even other ouputs can have the Triac only switch on the DC side of the incoming waveform depending on the version (example, C08 VS C07). As such, entirely possible is all you have is an LED and dropping resistor, if you wire it one polarity it works, and the other polarity it doesn't. Might be worth double checking that before assuming the output is dead from the board- or test with an original bulb. Also, might require slight capacitance (Edit- or just resistance via a load resistor) to ensure the TRIAC is triggering. You might be chasing tail when the problem is your LED setup.

Last edited by Jetguy

While this is a different engine, details like knowing the same basic TRIAC circuit is powering that light output, we might find the fix here. https://ogrforum.ogaugerr.com/...rx-led-light-problem

Here is a key answer from that:

The 680 ohm resistor is required to give the triac enough "leakage" current to fire, it won't fire without some sort of resistive load.  This is common and happens on the R2LC as well.

 You can get AC out of the light output in conventional mode, or when the locomotive thinks it's in conventional mode, so you need the diode.  I mistakenly omitted the diode in early LED conversions, and after a few months the LED's started dying, apparently from reverse voltage spikes in excess of their reverse voltage ratings.

 You need both the resistor and the diode.  Also, as GGG says, for some firmware you could reverse polarity on lights, I don't know if that applies to the LCRX as well.

Again, the bottom line, a load is needed to ensure the TRIAC triggers. That is the purpose of the 680 Ohm resistor across the output of the board, then, after that, comes the diode to prevent exceeding the PIV (Peak Inverse Voltage) of the LED, and then in series, the  current dropping resistor (example 1K). So a complex parallel and series circuit. I'm sure somewhere I saw capacitors could also be used, but did not yet find that previous post reference. My own testing when messing with that C420 engine was that just capacitance from my fingers on touching contacts on the LED leads was enough to trigger the TRIAC and suddenly the LEDs lit up.

Here's my take on what is needed to both trigger the output with the 680Ohm load and protect the LED from PIV.

(+) -----------1001N1->-----1K ohm-----

      |                                                     |         

680 ohm                                            LED

      |                                                     |

(-)-----------------------------------------------

 

Last edited by Jetguy

Or another easy way in testing, put your LED and the original bulb in parallel. The bulb loads the circuit so there is then power, and then the LED would also light. Just proves that the resistor would work.

Also, if you just try to test the output socket with a meter- for the same reasons the LED doesn't light, your high impedance volt meter might not register voltage on the output leading you to a false conclusion the board is bad or not outputing.

Last edited by Jetguy
Jetguy posted:

Or another easy way in testing, put your LED and the original bulb in parallel. The bulb loads the circuit so there is then power, and then the LED would also light. Just proves that the resistor would work.

Also, if you just try to test the output socket with a meter- for the same reasons the LED doesn't light, your high impedance volt meter might not register voltage on the output leading you to a false conclusion the board is bad or not outputing.

Wired the lights in parallel and the LED lights up for a second when power is applied then goes out so I'm getting somewhere. 

Forget the resistor across the outputs, use a .01uf 50V capacitor.  That give the triac the load it needs to fire, but doesn't consume power all the time.  This is how the ERR products handle the lighting outputs, and I also do the same on my Super-Chuffer lighting input line.

Obviously, you'll need a series current limiting resistor, for TMCC LED's, I use 470 ohms 1/4W.  Finally, the positive lead of the LED goes to frame ground as the TMCC lighting output is negative in respect to the frame.

Hey guys,

I know this is an older thread, but can anyone tell me where to connect the black and brown wires that are shown in the left of this picture? I'm repairing the same loco, I basically had to rewire most of it. I got everything else working except the headlamp. If anyone can help I'd appreciate it.

Thanks,
Scott

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Last edited by Scottmaster8809

Hey guys,

I know this is an older thread, but can anyone tell me where to connect the black and brown wires that are shown in the left of this picture? I'm repairing the same loco, I basically had to rewire most of it. I got everything else working except the headlamp. If anyone can help I'd appreciate it.

Thanks,
Scott

1

IIRC, the wires go from the R2LC and to a plug to the headlight bulb.

Thanks for the replies guys, sorry if I was a little vague in my description. I know the wires are for the headlight bulb. This is for a TMCC loco. I think the brown one connected to the R2LC but I'm not sure where. Does the black one also connect to the R2LC or to the frame ground? I tried looking up a wiring diagram but I'm having trouble.

Scott

Last edited by Scottmaster8809

John,

Unfortunately, I don’t have an ohmmeter. Although, I probably should have one for a project like this. I bought this loco used thinking it might need some repair, but I didn’t realize how extensive it was going to be until I opened it up.

Also, I think I was mistaken about the brown wire going to the R2LC. I think the brown wire for the headlight might have come off of a leoco connector to the PCB. I thought this might be for the TMCC directional lighting and for the headlight flashing when programing the loco/momentum settings.

I circled in red where I think the wire originally came from on the PCB, but I’m not certain. Do you know where I can find a pinout for the PCB? I can’t seem to find one.

Part Number: 691PCB10B9
Part Name: MOTHERBOARD / ENGINE / K-4 PACIFIC
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Looks like the headlight to me.  Note that the ground is right next to it, conveniently placed.

I got this from Rod's excellent TMCC Motherboard Document, I've attached it here.  A very useful reference for working on many of the TMCC locomotives.

Motherboard Connections R1.31.pdf

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Last edited by gunrunnerjohn

Thanks John, I really appreciate it. that's exactly what I needed. Now I just need to crimp some new wires to add to the connector and it should be good to go.

I found these older threads on here where you posted about the connectors that Lionel uses and one where you posted about the crimping tool you use. Very valuable information. I think I'll order some of the connectors and crimps from Digikey and the crimping tool for any future repairs.

https://ogrforum.ogaugerr.com/...ind-leoco-connectors

https://ogrforum.ogaugerr.com/...-legacy-tmcc-engines

Scott


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