Smoke output on LGB Heidi



15 Jun 2011
Hi all,

I am trying to improve the smoke output on a LGB Heidi 20272. It is factory fitted with decoder and sound. What I was planning on doing was to fit a relay to the existing smoke output in place of the existing 5v smoke generator. I would then use the relay contact to switch track voltage to a 24v smoke generator.

What I am struggling with is that the smoke output is modulated, I assume to reduce the voltage but cannot ascertain the CV to adjust the value. I have been unable to locate any information about the decoder on board. I have attached a picture of it. I have tried looking at it with JMRI. It reports as a Massoth Type 35. If I connect an LED across the smoke terminals (1K resistor) in series it turns on and off with F7. I am doing this using my NCE controller so the track voltage is low (13v)

I have looked at the output with a scope and I get a peak voltage of around 1.8V which will result in poor performance of the 5v generator so if I can solve this it might be that the 5v unit is OK.

Any assistance would be appreciated.



Neil Robinson

Neil Robinson

24 Oct 2009
N W Leicestershire
IF (big if) the decoder is what I suspect it is it will be CV 49 that sets the voltage for the F2 (smoke) terminals. A value of 32 (max value) should give full voltage with a value of 6 or 7 ish giving 5V Setting CV57 to 15 allocates the F7 controller button to operate the F2 output terminals.

However I suspect the smoke unit supply part of the board may have blown so the above is rather academic in your case. :(


Clencher's Bogleman
25 Oct 2009
North Essex
An alternative solution, have you considered one of Massoth's new "round boiler" pulsed smoke units to significantly improve the smoke output? Inbuilt decoder, so no need to fiddle with exisiting loco settings, plus the option of "cylinder smoke" if you want it.

Neil Robinson

Neil Robinson

24 Oct 2009
N W Leicestershire
o_O that a lot of info ..
Grovelling apology,
I now concur with John S.
Goodness knows which decoder details I looked at earlier ( post 2) but when I revisited my Massoth files they state CV 56 for voltage selection and CV57 for command allocation as per John's post.


G Scale, 7/8th's, Electronics
5 Jun 2013
Tamworth, Staffs.
The 'voltage selection' CV is a divider of the track voltage..

So, dependent on your Central Station (and power supply) you may find a value of '6' gives you a better smoke output?


28 Jan 2010
Eastern MA
Measuring the voltage with a meter can be mis leading as the power is reduced somewhat like PWC by the decoder. That is a Short pulse of full voltage is applied to a smoke unit and when you change the cv you are changing the pulse width, wider gives a higher voltage. This needs to be measured on a Scope for pulse width, not a meter which may not read what the light bulb is using.

I would use a 5 volt bulb to see the brightness as this is easier than waiting for a smoke unit to heat up and work.