# Bachmann K-27 - which wires are the optical chuff?



## jimtyp (Jan 2, 2008)

I want to install a Turbo Smoke unit in the Bachmann K-27. The smoke unit has inputs for a trigger and ground so you can have the puff in sync with the chuff. Anyone know which wires are for the optical chuff inside the K-27 boiler?


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## Curmudgeon (Jan 11, 2008)

Now THAT is going to be interesting! 
Since the polarity in the loco in "wrong" for most sound system triggers, and it is not a simple make-break as a reed switch would be...... 

Hope you have spares! 

The three wires per side on the circuit board, floor of firebox, behind the flywheeel of the motor. 

At least that's where they WERE on the last 9 or 10 units through here.


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## jimtyp (Jan 2, 2008)

Thanks Dave! So I'd need an NPN transistor to get the polarity correct? You say 3 wires, do you know which ones are which? And what color they are?


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## Curmudgeon (Jan 11, 2008)

Different colors on each side. 
Power, ground and signal, not sure without looking which is which. 

You MIGHT be better off coming from the tender, especially if you have already inverted the signal in the tender for your choice of sound systems. 

There are more wires that you really need from engine to tender (I remove 5 of them), so choose what you need. 

You radio/battery on this one? 
Use the power pickup wires. 

Remove them from the plug on the lower firebox board and connect to the smoke unit, and WHACK them off the Ames Super Socket, parallel to the chuff inputs to your sound card.


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## jimtyp (Jan 2, 2008)

I'm using track power. Thought about coming from the tender to the smoke unit in the boiler since I already have a P5 working off of the optical chuff, but not sure which wires I could use?


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## Greg Elmassian (Jan 3, 2008)

Use the same wire that you use to trigger the Phoenix. The TAS smoke unit has a diode in the chuff lead. 

Regards, Greg


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## jimtyp (Jan 2, 2008)

Greg, that's what I want to do. The problem is the wire I use to trigger the Phoenix is in the tender, but since the smoke unit needs to be in the boiler... So I'm trying to figure out which wire is the chuff trigger? And which wire I can use as the chuff ground. Those seem to be the 2 wires the TAS unit needs. My understanding is the chuff does come from a sensor in the front cylinder?


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