TrainsAmerica/Atlas Smoke Unit Help

Somewhere between zero ohms and infinity, I would say.

That’s not two resistors that I can see, it’s a resistor and a thermistor. Sorry if I’m stating the obvious but TAS/Atlas smoke units have one resistor. Value of the resistor is I think around 22/24 Ohms. It looks pretty charred or covered in smoke fluid residue, as does the thermistor. Normally TAS units, in particular those used by 3rd Rail, have a ceramic coating, which I am not sure I can see in your photo.

The spacing between the thermistor and the resistor is important and is sometimes an issue with TAS units and indeed Lionel smoke units that have thermistors. But yours looks to be in the right place. It and the resistor have to be seated well into the smoke wadding and a sufficient level of smoke fluid maintained in order to function correctly.

Have you tried reading the resistor with a multimeter? If the wire winding has broken up it won’t function. If it reads OK, the problem might be either in the thermistor or the power supply to the resistor. With TAS units this was sometimes on a board  split off from the part in your photo. There are many posts by GRJ on replacing the relevant components and diagnosing which one has failed. I can’t recall whether it’s a voltage regulator or another part - the actual electronics are not my field!

Over fill with fluid, is another problem. (Atlas/TAS smoke unit pictured). The fan to the left can become fluid-logged. (Read the instructions)  Maybe about 1/8" to 3/16" between the thermistor and smoke resistor.  Thermistor was a low fluid level, cut-out, if it was working properly. There was also a fiber wad-ing in the fluid chamber.

The standard value of the TAS smoke unit resistor is 10 ohms, by size it looks to be a 2 or 3 watt resistor.  I have no idea the characteristics of the thermistor, I've never seen that published.  Since you have the bare smoke PCB, the controller board for the smoke is obviously the separate board.

If I were reviving that smoke unit in a TMCC engine, I'd lose the add-on controller board and just replace the resistor with a 20 to 27 ohm resistor, then you can run it directly from the TMCC R2LC smoke triac.

@gunrunnerjohn posted:

The standard value of the TAS smoke unit resistor is 10 ohms, by size it looks to be a 2 or 3 watt resistor.  I have no idea the characteristics of the thermistor, I've never seen that published.  Since you have the bare smoke PCB, the controller board for the smoke is obviously the separate board.

If I were reviving that smoke unit in a TMCC engine, I'd lose the add-on controller board and just replace the resistor with a 20 to 27 ohm resistor, then you can run it directly from the TMCC R2LC smoke triac.

Hi John,

I've got a similar situation going on with my Weaver New Haven I-4 Pacific. The engine is equipped with a TAS smoke unit and what's happening is the smoke unit fan runs but the heating element crapped out and now there is no smoke at all. When you replace the heating element with the resistors as you describe, do you also remove the thermistor or leave it?

Thank you

Peter

@Peter B posted:

Hi John,

I've got a similar situation going on with my Weaver New Haven I-4 Pacific. The engine is equipped with a TAS smoke unit and what's happening is the smoke unit fan runs but the heating element crapped out and now there is no smoke at all. When you replace the heating element with the resistors as you describe, do you also remove the thermistor or leave it?

Thank you

Peter

First, determine the heating resistor is open, then it depends  on the route you’re going, ….if you’re going to isolate the heating resistor to TMCC, then you ditch the thermistor, isolate the heating resistor, and solder in 20-27 ohm resistor and wire that only back to smoke output on the radio board. (corresponding pin on the mother board) …..if you’re going back stock, leave the thermistor be, and just replace the heating resistor.

Pat

@Peter B posted:

Hi John,

I've got a similar situation going on with my Weaver New Haven I-4 Pacific. The engine is equipped with a TAS smoke unit and what's happening is the smoke unit fan runs but the heating element crapped out and now there is no smoke at all. When you replace the heating element with the resistors as you describe, do you also remove the thermistor or leave it?

Thank you

Peter

That depends.  If it's just the resistor, then replacing it will be easiest as Pat states.

However, if the resistor is good, then it's likely something about the electronics has crapped out. This could be a problem as many times they're using the chuff input to the TAS smoke unit to control the chuffing.  First thing to do is to see exactly how chuffing is controlled before tearing the smoke unit apart.

   Peter, the NH I4 as originally cataloged was listed with TA EOB components. It was in a few flyers before it was delivered. By the time it was made it came with ERR cruise. I believe it was corrected in the last flyer. I’m not really into smoke features and have never opened it up to look. Not sure if ERR offered a smoke unit at one time. I do know the chuff is controlled by a cherry switch as mine needed some tweaking to get all 4 chuffs.

@Dave_C posted:

   Peter, the NH I4 as originally cataloged was listed with TA EOB components. It was in a few flyers before it was delivered. By the time it was made it came with ERR cruise. I believe it was corrected in the last flyer. I’m not really into smoke features and have never opened it up to look. Not sure if ERR offered a smoke unit at one time. I do know the chuff is controlled by a cherry switch as mine needed some tweaking to get all 4 chuffs.

I don't recall ERR ever offering a smoke unit as a product.  Also the chuff control I referred to is how the smoke unit is managing the chuffing smoke (if it even is).  The ERR product never offered anything for chuffing smoke control.  Not having one of these in hand, I can't really say what it has in that regard.

@gunrunnerjohn posted:

I don't recall ERR ever offering a smoke unit as a product.  Also the chuff control I referred to is how the smoke unit is managing the chuffing smoke (if it even is).  The ERR product never offered anything for chuffing smoke control.  Not having one of these in hand, I can't really say what it has in that regard.

Stock, they came with ERR CC & a TAS smoke unit,……chuff is cherry switch on cam. The TAS smoke puff feature is tied to chuff in via a one way diode……

Pat

@harmonyards posted:

Stock, they came with ERR CC & a TAS smoke unit,……chuff is cherry switch on cam. The TAS smoke puff feature is tied to chuff in via a one way diode……

Pat

In that case, he would need to get the stock TAS smoke unit electronics working again to get the smoke chuff.