Semi Smart Smoke Unit

If the audio is still good, that eliminates the chuff switch.  It's rare for the Smart Smoke itself to go bad, usually that regulator is the culprit.

If you're in there working on it, consider installing the Super-Chuffer II, it manages the smoke fan and gives you smoke at idle as well.  You can also take advantage of the optional features of Rule-17 lighting and automatic cab light control.  With the Super-Chuffer, you won't be using any of the smoke unit logic for controlling the fan, problem solved!  You'll also get a lot better chuffing performance.

Some of those units did not reset the timer on the chuff switch closure and the smoke motor can stumble at certain speeds if the motor pulse is longer than the switch closure.

Everything works on this engine and I have your chuff generator in it. I suppose I could put the SC in there and that would take over for the SSMU motor controls. I could mount it near the smoker under the shell and take your nice little 5V power supply out.

Carl, that makes sense. Wonder if it was optimized for the original 2 chuff per rev...?

That sounds like it's the problem Carl, the output of the Chuff-Generator at four-chuffs/rev could fall into that area.  The minimum length of a chuff output is 10 milliseconds, and it's variable up to 200 milliseconds in length as you slow down.  The chuff pulse is dynamically adjusted based on the spacing of the previous chuff to the current one.  I was trying for operation that would somewhat mimic the mechanical switch in case someone was depending on that. 

I have to be honest here, the Chuff-Generator was really only characterized to mate with the Super-Chuffer, the other stuff was just a guess based on limited information about what might be required.  A number of people have used just the Chuff-Generator with a 5V supply, and I've never gotten any feedback of issues.  However, I believe most of them just wanted the 4-chuffs for audio and either had Seuthe smoke or weren't interested in smoke operation. 

I guess in my tunnel vision view of the world, I couldn't imagine wanting the Chuff-Generator without the Super-Chuffer.

Well, at least I can separate out all the functions of this unit. The element control via the ACRG is good so that will stay intact. I'd imagine that this unit was engineered to work with the original 2 chuff per rev microswitch but it's interesting that the chuff input to the SSMU is coming in via serial comm. 

In any case, I am going through my roster and fixing up a few things. Smoke units always seem to cause more grief than they're worth. 

You'd think the chuff on the serial data would not be dependent on the specific timing of the chuff pulse.  AAMOF, I'm not sure how it could be, but who knows.

You won't get any argument from me, smoke is always one of the high maintenance items on the list.

Wonder if the serial is loaded down on this engine like most of Lionel's. You've got the ACRG, the SSMU, the IR tether and the DCDRS all yanking on it. Maybe the SSMU is a bit hard of hearing? 

Quite possible, I wonder if there's any buffering of the serial data?

All the serial wires are wire nutted together and referenced to chassis ground from what I can tell. 

Well, the serial data is ground referenced.  If they're all connected at one place and track back to pin-24 on the R2LC, then there's no buffering.

It's right to the m/b. The closest wiring diagram would be the 0-8-0s in Supplement 47. 

Interesting that I used your CG in the TMCC 611 with no issues triggering the SSMU. Also the first L2a Mohawk.

Given it's using serial data for the smoke trigger, I can't imagine it's the C-G that's the issue.  The length of the chuff pulse shouldn't be an issue.

I have the same Lionel Y3 with Railsounds 5.  Its on my hit list to get upgraded to 4 chuffs.  Currently its still all stock with 2 chuffs and I have the same exact problem.  At very slow speeds the smoke puffs in sync.  As it starts to speed up, it starts missing a puff sporadically.  Eventually it will only occasionally puff.  Stopping the loc and then starting it again, resets the smoke puffing and the same thing will happen again. I'm interested if you figure out what the cause is so I can fix mine.

Same fix Joe, Super-Chuffer II.  I can say with certainty that issue will be gone after that installation.   The 4-chuffs is neatly addressed using the Chuff-Generator, a one-stop solution.

Unless the SSMU wants to see some persistence in the chuff signal, I'm stumpered as to why it drops its puffs. In any case, GRJ has the elegant solution plus it will now have smoke at idle. I will update when I get the SCs. 

I wonder if they're actually sending out the chuff signal on the serial data for the duration of the contact closure?  I don't have one to actually look at, does the chuff change it's duration when you are running slowly?  Maybe the code in the smoke unit processor is just screwing up.

The chuff switch duty cycle is variable being cam-driven. So it can be on or off the whole time at zero speed. The switch state change duration is shorter with at higher speed. How it triggers the chuff message is beyond me though. If it's a true one-shot trigger with change of state or if it constantly transmits based on the switch state. 

I've never examined the chuff data in the serial data, might be interesting some day.

The Super-Chuffer varies the chuff duration based on spacing of previous chuffs.  It's also edge triggered, it doesn't care about the duration of the chuff signal once it sees an edge.  I do have a maximum length of chuff that's active at very low speeds, and also when you reach a speed of 20 chuff/second, the fan runs continuously.