I just installed a TAS EOB in my AC-6 and I'm about to wrap everything up but I found it doesn't have voltage (directional or constant) at the front and rear light outputs on the TAS board. Question: Does anyone know where the directional lighting voltage comes from? Is it socket powered by the mother board and turn on/off through the R2LC? TAS manual states it should be 12VAC so I'm assuming it comes from the main PCB. Possibly a bad triac? Any help will be greatly appreciated. 

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The lighting outputs come from the R2LC, they are just carried by the TAS motherboard to the connectors.  Unless the traces are cooked on the TAS board, the issue is the output from the R2LC.  If you are using LED lighting, you need to add some 0.01uf load capacitors across the lighting outputs of the R2LC.

Thanks Mike. I'll give it a try later on. I may have fat-fingered the buttons at some point.

GRJ, I'll try one of my other R2LC's and see if that does anything. What pins on the R2LC should the ceramic .01µf capacitor be soldered to for lights? I do plan on running LED's. Is the R2LC just not seeing the resistance in the circuit therefore not sending voltage through? FYI; the mother board traces look good and I have continuity through the circuits from one end to the other. 

I suggest putting the caps on the connector pins so they're there if you swap the R2LC for any reason.  Pins 3-4 are ground, and pins 9-10 are the rear light output and pins 13-14 are the front light outputs.  I lay the caps right on the motherboard and wire them to the pins.  If you keep them close, the R2LC won't interfere with them.

R2LC Pin Assignments

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GRJ, Since the R2LC is the last board on the mother board, couldn't I just solder them to the underside of the mother board at the corresponding pins? There's a lot of room between the aluminum heat sink "foot" and the bottom of the mother board. It doesn't matter where they're attached as long as the capacitors are bridged between pins 9&10 to 3&4 and 13&14 to 3&4, correct?

Refresh me on the caps for R2LC, plenty of Lionel and Atlas engines used LED that were just a Diode, resistor and Led in series as HL? G

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George, some of those didn't work reliably.  I suspect somewhere there's either a cap or resistor load.  Obviously, if there's a bulb on the circuit as well, that will do the trick.  FWIW, I've seen engines come in that had just an LED, and sometimes they'd light, and sometimes they wouldn't.  For reliable operation, I just pop the cap in and all is well.

It's well known that an LED alone doesn't trigger the triac as it doesn't present a load until it gets to around 2.5 volts.   In years past, I used to use resistors, but then I found out that the capacitors worked as well, and they don't present any load (or get warm).  The ERR TMCC boards all have the .01uf caps across the outputs as a standard feature, they're built into the board.

Right, but you could not just use an LED on a R2LC output they had a diode for protection and a 1K ohm resistor to limit current.  Never knew there was a reliability issue with Lionel and Atlas engines with these features?  So I assume the 1K resistor was enough of a load with the LED to operate reliably.  I have never had issues mimicking the OEM approach.  G

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That isn't enough.  I can't say what they had as I don't have one to look at.  I can say that whenever I do strictly LED lights for a plain TMCC locomotive, I have to add the caps or I get no lights.  It's been mentioned here countless times in various threads.  I've proved this to myself multiple times, so I'm pretty sure that's fact.  Also, why would Jon Z. have added the .01uf caps to the Cruise Commander if he didn't need them.  That's certainly not like Jon to drop in unneeded components.

Update on lighting issue:

I installed the caps on the mother board pins that go to the R2LC. The LED lights work! They are directionally controlled too. However, the headlight strobes upon startup and continues to strobe until I press the boost button. The headlight and taillight will not directionally function until I hit the boost button. I can spin the red throttle wheel up or down in forward or reverse increasing wheel speed and the head light will only strobe until the boost button is pushed. It seems a bit weird. After I pressed the boost button and gained the proper function of the headlight and taillight, I then tested the Aux1 & Aux2 headlight on/off function and it works too. Under normal operating, the headlight stays on in forward and reverse with only the tail light illuminating in the reverse direction. Oh yeah, I had to flip the polarity of the LEDs to get them to work. Initially I had the anode soldered to the positive wire of the wiring harness. They ended up working with the anode attached to the negative wire denoted on the motherboard. I used a 470 & 510 ohm resistor in series on the cathode sides of the LEDs. Thanks again GUNRUNNERJOHN for your guidance.

Dan

Yeah I thought it was weird too. Maybe has something to do with the programming being corrupted in a chip on the motherboard? I know you can set the Aux1 code in other Lionel TMCC locos to cause the headlight to strobe. It depends on what the outputs are used for. But you already know that. Lol. This R2LC has a .01uf cap bridged across pins 3&4 to 5&6. I tried another known working R2LC and it performed the same way. If I every figure out why, I’ll let you know.

I bet if you remove caps it will work.  There are some old notes on certain boards how the use of various buttons flipped the out puts or allowed DC on. Someone a long time ago wrote something up, they even used it to control different colored LEDs if I remember right.

The polarity issue is typically the biggest issue with the LED on TMCC.  G

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