No Smoke Fan operation no voltage off motherboard molex to fan motor

The fan power supply is on the smoke unit, so the first thing to do is to see if it's putting out 5V when the smoke it turned on.  You should find 5VDC on the circled pin with the smoke turned on.  If the heater is getting hot and you don't have 5V, the power supply on that board is bad.

Hello, Thank You for your quick reply to my issue, This is supposedly a Brand New Smoke unit, I purchased it to replace the other one that was doing the same thing, I don't know if this has any bearing but I noticed a black wire coming from a board inside shrink wrap that appears to be cut. I don't see any black wires that are not attached to something already and not being that familiar with Lionel am not sure if this is supposed to be like that, my guess is that it is not.  I just find it hard to believe that I could have two bad smoke units, not impossible I know but want to make sure that there isn't another underlying issue causing the boards not to function. I am not seeing any voltage on that pin and verified that the heater unit is still indeed working.

Any ideas?

Thanks Paul

That's common, the smoke regulator has two grounds, and many times one is simply cut off as there's no good reason for two.  The four wires are all that's necessary.

If the heater is getting power and getting hot, the regulator is fine.  If the heater is not getting power, the regulator is one of the top suspects.

OK thanks for the clarification, I guess I'll be ordering another smoke unit.

Any idea where I can purchase another Smoke Unit PCB/Smart Smoke 691-SSMU-FS1 ?

The place where I got the last one is out of stock and Lionel website says they are unavailable.

You can probably fix that one, the regulator circuit only has three parts, the regulator, the cap, and the diode.  The failures are usually the regulator, followed by the cap, and then the diode.  Replace the LM78L05 regulator first, if that doesn't do it, move on to other components.  You can actually check the voltage on the outside pin of the regulator and see if unregulated voltage is present, my guess is you'll find about 15 VDC there.

I appreciate the info, unfortunately the arthritis in my fingers prevent me from doing any component level repairs, any idea where I may find a new unit for sale? 

Not if Lionel doesn't have them.  What is the exact part number on the PCB of your unit?

I'd consider finding someone that would be able to fix it.

Just a point of clarification for this particular model (6-38094): The fan unit is off when the locomotive is in neutral or idling. The fan only turns when the locomotive is running. That’s the way it was designed. 

Thank You for that info, I appreciate it.

Paul M.

Jim, that's why I do these with the Super-Chuffer.

gunrunnerjohn posted:

Jim, that's why I do these with the Super-Chuffer.

Very good candidate for the GRJ special.