SD70M-2 Smoke unit

Silly check but have you checked the connectors and measured for any resistance? Also the power board on the smoke unit could be failing. I have had that happen also.

If your cab 2 has no control, do a continuity test placing one probe on pin 23 on the R4LC and the other on the antenna.  Confirm continuity.  Your locomotive has an AC smoke regulator.  Those go bad.  It has 5 wires.  One (usually brown) for serial data (pin 24 on R4LC) one roller hot, one chassis ground, one smoke unit hot and one for smoke unit ground.

The big question is--after you programmed the locomotive and pressed set, did you then press again the engine number then aux-1 then the number2.  This tells the R4LC what it has to do.

Thanks Jeff & Marty,  I just finished up with a continuity test of the antenna. My meter showed .001 ohms resistance from the antenna plate to Pin 23 on the receiver board.  That is issue #2 video with a new R4LC board installed. Bad board I think. Marty, Are you referring to the heat shrunk board mounted to the front of the chassis 691ACRG103 AC REGULATOR (S03 CODE)? If so, Are there any tests that can be run on it, or is it simply a signal corruption issue and it just gets replaced?

  With regards to programming, Yes I did. I followed the instructions on page 23 of the manual. (Sorry, wasn't clear in the video)

  You have identified the AC smoke voltage regulator.  To test output, you will notice on top of your smoke unit board where three connections are made.  These are side by side.  The outer two are AC hot from the voltage regulator.  The center is ground from the reg.  With your locomotive powered up, take your meter set to AC voltage and you should see 9-12 VAC at the points I mentioned.  Anything under 9VAC is not good.  

If you have to get inside the shrink wrap, look at the brown wire and do continuity to pin 24 (serial) on the R4LC board. That will be on the end.  Next to the serial wire is AC chassis ground.  Next to that is AC roller hot.  Next to that is the smoke unit ground and the last wire is the smoke unit hot.  

If you have no smoke unit operation, do a continuity test to all 5 points on the reg to where I told you they connect to.

I did my E-7 last week measuring 8 VAC at the smoke unit.  It would give out a small lame bit of smoke.  I put in a new reg and life was good.  If you ever have to replace a reg, cut and splice the wires.  Do not try to solder wires to the reg board.  

I have a little box of bad regulators, they seem to be dropping like flies lately.  It will be no surprise if it's the regulator.  The ones that don't have the triac bolted to the frame seem to cook the triac with some regularity, I've actually repaired a couple by replacing that part.

The a/c voltage reg took care of the issue. Thanks again