Just wondering about MTH smoke units and changing resistors

Don't do it!  The PS/2 and PS/3 logic is tuned to the value and power rating of the stock resistors.  Changing them can only result in bad things happening.

FWIW, I'm curious why you feel the need to get better smoke?  Usually, MTH is regarded as the smoke champ, and if you're getting anemic smoke, my guess is you need smoke unit maintenance, not tinkering with the smoke unit design.  Properly maintained, the MTH smoke is the best around.

John, I asked because I figured one of you guys with knowledge would answer. Thank you for being so quick. Nice to hear this before heading to the office

I do need to change the wick out, as my smoke output is not as strong as it use to be. Especially at slow speed. I like to run steamers slowly. So maintenance is on the horizon soon.

The reason for the question stems from the fact that I will already be in position to do a change of resistors "if" that was a good thing to do. My curiosity comes from watching the Dynamic smoke videos of KM models and of the guy that upgraded resistors on his 1 gauge Hudson (You Tube).  Having some experience with electronics, I figured there must be an inherent problem doing this with the board, as you confirmed in your answer.

Another member stated in a post I read on the forums some time ago that he does "upgrades" by enlarging the air input hole. That immediately sounded like a better idea to me. Lastly, I agree that MTH has the best regular production smoke. Again, I appreciate your thoughts.

-Todd

For Lionel smoke, there is a kind of "standard" package of enhancements for smoke, including enlarging the smoke intake hole.  For the non-regulated ones with the 27 ohm resistor, I change it to 20 or 22 ohms for better smoke, use better wick, and insure good airflow over the resistor/wick to the stack.  I also enlarge the stack output if possible.

For MTH, I don't think I've ever bothered enlarging the intake as I always got great smoke by doing basic smoke unit maintenance.  Top on the list is to change the wick.  One issue with MTH smoke is the impeller gets loose on the motor shaft, so that needs replacement at times or you don't get good smoke when moving.  If you have great smoke at idle, but it is poor when moving, that's a prime suspect.

John do all the railking engines have two heating elements or Resistors one  low-voltage and the other higher

@finbar posted:

John do all the railking engines have two heating elements or Resistors one  low-voltage and the other higher

No, which is why I ask what specific locomotive we're talking about in conversations about smoke.  There are two sizes commonly used for MTH O-gauge PS2/PS3 locomotives, usually the two-resistor model, but some have the one-resistor model.

It’s the o gauge ps1 type with fan and the two resistors under the board. I have a brand new engine that’s been in the Box for years and was testing it to make sure it was In working condition and noticed it didn’t smoke at 6 volts only at 12

The PS/1 smoke unit should smoke at around 7 VAC, but it needs that at a minimum to get going.  The headroom of the regulators, etc. need a certain minimum voltage.  By the time you reach 8 VAC, it's going pretty strong.  At 6V, the smoke fan is struggling and there's barely any smoke.  The smoke unit is also only using one resistor at low voltages.  At around 12-13 volts, the regulator circuit shifts gears and both smoke resistors are in the picture.

I recommend you do NOT try to change the value of the resistors in a PS/1 smoke unit, the regulator circuit was designed around the standard values.

Biggest culprits for weak, or poorly operating MTH smoke units are charred batting, dead resistors, ( that’s obvious ) improper fluid use, gumming up the works, dead fan motor, detached fan impeller,  or the air flow gasket missing or misaligned…..( seen this a few times on early units with the wrap around rubber gasket )  Biggest culprit I’ve seen lately are fan impellers spinning on the shaft ( loose ) they’ll work ok at smoke idle, but chuffs get blah because the motor spins, but the impeller just sits there,…..other than the above mentioned errors, John’s replies are spot on…..

Pat

Sorry for the delay John. I know one of the resisters is not getting hot as I took it apart and started it up. There was no smoke at 8 volts my question is are both the resistors the same value 16 ohms 2 watts or are they different. I can only find part number A 10000018 16 ohm 2 watt $2.50 on the MTH a web site

This is NOT Proto sound  1 engine it’s just with whistle if that makes any difference

Well, you don't change the smoke resistor values in PS/2 or PS/3 either, but you mentioned PS/1.  It helps to know exactly what we're talking about...

Thanks John but I just wanted to know if both resisters are the Same value 16 ohms 2 watts on that PS 1  board or is it different and what the value is and or a part number for it at MTH. I could only find the A10000018 16 ohm 2 watts

@finbar posted:

Thanks John but I just wanted to know if both resisters are the Same value 16 ohms 2 watts on that PS 1  board or is it different and what the value is and or a part number for it at MTH. I could only find the A10000018 16 ohm 2 watts

They are the same 16 Ohm.

All the MTH full sized smoke units for O-gauge have the same resistors, 16 ohm 2W.

@finbar posted:

This is NOT Proto sound  1 engine it’s just with whistle if that makes any difference

YES, that is a PS1 smoke unit- because you have LESS than PS1- aka DCRU- that doesn't control or power the smoke unit, thus it is a PS1 style standalone smoke unit directly track powered.

Theory of operation of a PS1 smoke unit- BELOW the threshold voltage- ONLY 1 resistor heats!!!!!!

@finbar posted:

I know one of the resisters is not getting hot as I took it apart and started it up. There was no smoke at 8 volts

Highly, highly,highly suggest you read this topic https://ogrforum.com/...ut-on-ps1-smoke-unit