# Bachmann K27 rewiring sanity check



## Darrene (Jan 13, 2020)

Hello all,

I'm embarking on the third of my battery RC DCC conversions and this is proving the most challenging. I'm after a bit of electronics advice.

My conversion path is Revo DCC receiver and tool battery driving an ESU XL decoder with smoke output. I've already successfully done my Mikado and Shay - I'll post the conversions on here for interest.

Anyway... I'm taking this one a bit further with an animated Johnson Bar and rear decoupler.
I'm done a fair bit of the work but would ideally like to interface the decoder to the chuff circuitry. (The ESU is hugely configurable in most respects, including the auto-chuff but I prefer an electrical trigger if I can use one). At the moment I've paired the original Bachmann circuitry back to the motor/chuff board just behind the motor and the distribution board / resistor & regulator board above it, under the cab.

Referencing Bob Grosh's hugely helpful schematic, the outputs from the two optical triggers each come through a diode, and are joined (via JP1 - I'm unsure what this is) to provide a common output at the tender

This output will need to be inverted for the decoder, which expects to see supply voltage for a chuff trigger. So I could achieve that by;

Connecting a 2N2222 NPN transistor BASE pin on the common chuff output
Connecting the 2N2222 EMITTER pin to ground.
Connecting the 2N2222 COLLECTOR pin to the decoder chuff input


Does that sound reasonable?


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## Greg Elmassian (Jan 3, 2008)

yes


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