# Bachmann Mallet, DG583 decoder & smoke unit?



## ntpntpntp (Jan 14, 2008)

Hi all,

I have a Bachmann 2-6-6-2 Mallet loco, it's been running for some time with a DG583S decoder wired through the supplied adapter board, but the smoke unit has never worked regardless of the position of the DC/OFF/DCC switch in the smoke box. I refitted the DC board yesterday and proved that the smoke unit itself works fine. I also tried a plug-and-play DG583AR decoder - no smoke control with this either.

Is there some additional decoder wiring I need to connect to get the smoke unit to work with DCC with these Digitrax decoders? I don't mind if it's controlled by the smokebox switch rather than a DCC function. 

I notice that there is a "smoke -" wire on the adapter board but I don't know if/where that should be connected? I did try connectng the ground wire on the DCC adapter board to the decoder, however this wasn't a good idea: It caused the smoke unit to function on DC on my rollers, but on DCC it made an unusual buzzing sound and blew a capacitor on the main board with an impressive "pop"! (I've got a replacement capacitor on order from my local electronics repair shop)

From what I've seen, others have smoke working ok under DCC - but maybe using a different decoder (eg. QSI?)

Hope someone can advise?

Nick


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## Greg Elmassian (Jan 3, 2008)

I forgot what pins Bachmann put the smoke unit on. In an Aristo loco, there are 2 pins defined tot turn smoke on and off. Normally they are just jumpered and you use the separate smoke switch. 

Bachmann copied the Aristo pinout, but not exactly. I think you are assuming that there was a way to turn the smoke on or off with the decoder. 

You have to make changes because: 

1. No standard for where the pins to control smoke are. 
2. No standard for what voltages to do the control. 
3. Your decoder has no high current output to run the smoke unit. 
4. I do not believe the function outputs on your decoder come out to the pins (other than front and rear lights) 

So, the easiest way to do this is put a relay in and wire it to turn the smoke unit on and off. 

Run the relay from a function output on your decoder, making sure not to exceed the current rating of your decoder AND MAKE SURE you add a "snubbing diode" across the relay coil to avoid destroying your decoder's output with BEMF. 

Regards, Greg


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## ntpntpntp (Jan 14, 2008)

Hi Greg, many thanks for your reply. 
Bachmann copied the Aristo pinout, but not exactly. I think you are assuming that there was a way to turn the smoke on or off with the decoder. 

I'd be perfectly happy to have the smoke controlled by the smokebox switch. On the main board drawing there is labelled a "smoke unit power transistor" which made me wonder if there is supposed to be a means of controlling the smoke via a DCC function? The documentation says the smokebox switch in the DCC position controls the smoke unit function via the plug-and-play socket, but it's not clear whether this means as a function output (via the power transtor?) or simply acting as a jumper. You have to make changes because: 

1. No standard for where the pins to control smoke are. 
2. No standard for what voltages to do the control. 
3. Your decoder has no high current output to run the smoke unit. 
4. I do not believe the function outputs on your decoder come out to the pins (other than front and rear lights) 

So, the easiest way to do this is put a relay in and wire it to turn the smoke unit on and off. 

Run the relay from a function output on your decoder, making sure not to exceed the current rating of your decoder AND MAKE SURE you add a "snubbing diode" across the relay coil to avoid destroying your decoder's output with BEMF. 


I'm tempted to simply disconnect the smokebox switch and smoke unit from the Bachmann main board and hook directly to track power, assuming the smoke unit will be ok at full track power voltage. That's how my other DCC converted locos deal with smoke units: I don't bother with using a DCC function. It's just that there seemed to be some sort of provision already built into the main board in this case, especially given the presence of the power transistor. 

Nick


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## Greg Elmassian (Jan 3, 2008)

I'm doing some projects today, so no time to do the research right now, but there's got to be a schematic of the socket somewhere. 

I don't know if they copied the aristo pins to turn on the smoke. 

Based on the experiences of others, I'd rewire directly to the track leaving the smoke switch inline. 

Why not google for the schematic? 

Regards, Greg


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## George Schreyer (Jan 16, 2009)

The pins on the DG583 only bring out the forward and reverse headlight functions. If you want to control the transistor on the bachmann board that drives the smoke unit, you will need to wire it to one of the function leads on the 9 pin JST connector that plugs into the side of the DG583. Refer to the instructions that came with the decoder to determine which function wire to use based on what function button that you want to use to control the smoke. 

Actually, you can use ANY wire except the white, yellow (headlights) and blue wire. The other 6 are available and can be remapped to any button that you choose. 

Just as an aside, the DG58x series decoders REVERSE the sense of the white and yellow leads. This was probably due to a "late" change in the definition of which head pin controls which light made by Aristo. Digitrax had to do some patching and it inpacted their board layout and therefore the assignments of the redundant headlight wires. In the "S" series with screw terminals, these are the ONLY headlight function control outputs so users of the DG583S have to deal with it by wiring the front headlight to the yellow wire and the rear headlight to the white wire.


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