sd 70 problem with smoke

Did you check the smoke resistor?  How about replacing the wick?  The smoke regulator is most likely the top suspect if you've checked the smoke unit as mentioned.  These are a fairly common failure item.  The fact that the voltage changes when you change the setting suggests that the serial communication is taking place, but the triac isn't up to handling the current.

Note that measuring the power is somewhat problematic with cheap meters as it's a chopped waveform.

Thanks for your reply. Wick Or resistor? Resistor ohms good. I just think that the chipset tells the ac reg how much voltage to send according to each setting. I don 't think the ac reg determines how much voltage to send. More just on or off with how much determined by chipset.

 I wish I knew for sure.

Actually, the AC regulator is the thing that is actually going to generate the voltage.  As far as the R2LC, it just sends serial commands to the regulator.  Since you have sounds, and the regulator is responding to the serial data after a fashion, I can't see this being an R2LC issue.

A long shot is a poor connection on the wiring to the smoke regulator, you should try to eliminate that as an issue.

I think they all must do this as I have a UP one and it smokes only after it has run for about 4 minutes and gets more smoke as it runs longer.  You can't but any more than 4 drops of smoke fluid in it or it will not smoke.  Very poor system.

i just rechecked it all- I dont see a problem. Thanks for the help

What is your item number?  You are saying Legacy SD-70 6-34612?  It is your AC regulator. If you have other functions like John stated, your R4LC is sending serial data.  I have replaced many of these for Charles Ro. 

Marty, he didn't believe me.

Iron-an sd 70?

John, I always believe you.  Many people give advive on the forum.  Some (you) give correct advice.

Marty, you had once given me instructions on exactly how to check this system. I have tested all wires for ac reg as well as smoke unit/resistor. You also explained that the smoke unit "should see 9-12 vac if reg is working. This,of course, is where the rub lies. I get <4v at smoke unit; although the voltage does change a bit between L M H.  So, the ac/reg can send voltage but just not enough? I figured it's failure to be not sending it at all. I wish I could read the serial data line as I read the serial data in cars-live!

   I have another sd 70 with smoke trouble. I just put in a new ac reg;however, no fix-and that's ok. I can still use the new reg-obviously. I bring this up because of the amount of trouble I have had with these smoke units since they were new. I see a number of folks with like concern. I've spent a fair amount on these smoke systems with it being the only thing that gives trouble regularly. All this being said I wish there was an alternative way to operate this smoke system- a retrofit of some sort that did away with this one. I have a few ac 6000's that have been virtually trouble free along with better smoke production.

 Thanks for the input, Marty and I surely thank you for the explanation. you gave. I've kept two copies!   

I would like it understood that it's not about"not believing" someone but more about understanding the explanation or reasoning. I want to know why or how, not just what the answer is. It's how I learn. Thanks to all.

I believe you could change the resistor in the smoke unit and rewire the smoke to be run from the R2LC directly, just like many other locomotives.  You wouldn't have the three levels of smoke volume, but it would work.

gunner- are you saying by-pass ac reg by wiring signal wire(serial) to smoke element? Change element to what?

That is questionable.  I believe his engine is Legacy.  It is easier to just replace the reg. 

You can't do this with Legacy R4LC.  The Smoke Triac does not respond to AUX1 commands.  It is always on.  G

Wow, takes me back to my TMCC board repair days. I have a couple of questions.

1) There is a regulator on the fan smoke unit PCB. I assume for the fan motor?

2) The AC regulator that is being talked about. Is it actually regulating AC to the

    smoke element (CHOPPED) control by the serial data from the RLC. There is a serial

    connection to this regulator>

http://www.tuveson.com/smoke-r..._smoke_regulator.htm

Here is a nice write up by carl. After reading this article/ Are you sure the right ohm

smoke resistor is being used.

Carl, Doesn't really give you much info on the regulator.  But...

Lionel has a lot of different smoke unit PCB boards.  Basic to semi smart and smart are terms used.

Many basic boards have a diode, cap and 5V regulator to take the AC input and make 5VDC for the fan motor.

The ACREG was added for some higher end TMCC engine to give you 3 levels of smoke.   The ACREG has AC input, serial data input and output to the heater element.  Still used the smoke unit PCB for fan motor voltage.  Typically these use 6 or 8 ohm resistors, where the basic stand alone smoke unit had a 27ohm unit.

The first Legacy (R4LC) all used ACREG since the Triac does not turn off on the R4LC.  Smoke is controlled by the ACREG.

Smoke units and boards have evolved even more with the latest Legacy board which are DC output based, not the AC output of the TMCC and R4LC Legacy engines (first generation). 

MTH really corned the smoke market with their setup, with just a few basic smoke unit types. G

I've just read the link Shawn provided. He says his meter reads 4.5 to .2.5v on ac reg output. Further says if it reads 4.2( approx) the it will eventually drop down lower to 2.8v. Sorry, I don't remember these figures exactly but they are close. This is exactly what my readings are on the ac reg out put. So, this means it's not 9-12 v --which is what I've been tryinmg to achieve. Sounds like I will put a new element in it and see what happens. Yes, I did ohm the resistor in my original testing. I have a new one on hand so I'll give that a whirl. Again, thanks to you all for the help-much appreciated.

Well, yes, for some reason I was thinking the TMCC version.  For Legacy you will indeed have to replace the regulator. 

I've done the mod to TMCC engines when the owner didn't want to buy another regulator, it's a simple mod.

Your post are always a pleasure. The scope is collecting dust in the closet...But, with write up like these. Who needs it.

Thanks Shawn.

Amos, If the resistance is correct, may be the batting is burned or not fully touching the element.

The fan may not be spinning the impeller properly.

The ACREG may be stuck on a low setting.  Follow the manual and set it to high after checking the other items.

Watch the smoke unit with shell off to see if impeller spins.  G

GGG-The fan is spinning,batting is new. ACReg "stuck" on low? Are you indicating there is something other than the 8,9 keys to operate the smoke unit? A procedure for unsticking the reg unit? I'll check it out. I put a new resistor in it last night but haven't tried it out yet-will today. Again, many thanks.

Yes, you can set the smoke to L, m, H using the momentum settings.  I think default is M, but it may be set to low.  What resistance is the element?  G

I ohmed this straight out of the lionel pack-9ohms-pack says 8 but it checks 9 for me. This is the first one of these i have used. I ordered these from Lionel for this exact product# loco and this is what they sent .The one I've done all previous work on came in a new Lionel smoke unit and checked at 8 ohms.

 Well, the new resistor has been put in and has been running for about ten min. so far no smoke.

I thought this loco called for a 6 ohm resistor-Llionel said it was this 8 over the phone.

 I'd like to find a 6 ohm resistor and try that out. I may call lionel Monday.

First PLEASE verify the actual Lionel item number!

Have we ever gotten the actual Lionel item number for this locomotive?  Marty posted Legacy SD-70 6-34612, is this correct?  If so, it requires a 6 ohm resistor, according to the part breakdown.  If you have an 8 ohm (or 9 ohm), I'd expect not much smoke.

(6-34612) Norfolk Southern LEGACY SD70 M-2 #2658

Let's assume 5 watts dissipation for normal smoke from the six ohm resistor.  If you change that resistor to a 9 ohm resistor, you'll only dissipate 3.3 watts.  That will result in very little smoke probably not enough to actually see.

I had said in my last post that the resistor that i've been testing on came in the smoke unit. i ordered it from lionel for that sd 70 according to the product number. this was a complete smoke unit assy. it worked fine for a while after installation until0of course-one day when it just uit smoking. i then called lionel and they asked for the loco product number and looked up the resistor according to it. they may have looked up a 6 but when it came the pack said it was an 8.   when the complete assy stopped smoking i ohmed the resistor and it ohmed  at 8 ohms. these are the verified specs on the parts. short story-it was smoking fine with the 8 ohm in it until it stopped. i can order some 6 ohm resistors and try one out. they could have picked up the 8's by accident and shipped them-who knows?

 btw-my caps key is broken as well as my cue key-the letter cue. sorry for the sloppy punctuation but this is the reason for it. thanks guys.

also-my product #is not 6-34612. it is 6-28334. when i looked at the breakdown for my kcs sd 70 it didn't break it down to the resistor-only to the complete smoke unit;hence,lionel looking further into it after i didn't want to buy another complete unit. again, i'll get some 6's. thanks.

It would have been a lot easier if we had the product number a long time ago.

If you looked at the product breakdown, you would have spotted this.

Clearly, the 8 ohm resistor is the wrong one if the parts breakdown is to be believed.

"It would have been a lot easier if we had the product number a long time ago"

 Ease up on the tone there, fella. I never meant to cause you bother and you are not obligated to respond. I also made it clear that LIONEL looked the parts up, not I, according to the product number, so yes-I believed them to be correct.