Reinstating DCC on a Bachmann G2 0-8-0

[MikeCW]

Can I have some advice please. I have acquired a Bachmann G2 0-8-0 from which the previous owner stripped out the decoder socket and blanking plate from the tender, and cut the wires between locomotive and tender, soldering them together for DC operation.

 

I have the original 12 pin decoder socket and blanking plate and want to reinstall these in the tender prior to fitting a sound decoder.  My problem is that I can't work out the locations on the decoder socket on which to solder the four wires between engine and tender. Although the four wires are, in fact, black, I will refer to them using the standard DCC  colour codes. They are:

Red -From right hand rail to decoder. Black - From left hand rail to decoder. Orange - Right motor brush. Grey - Left motor brush.

 

The decoder socket (without blanking plate) viewed from the top.

The four wires from the engine were soldered, from the underneath, to the positions L1, L2, L-, R+.

 

And the underside view.

Can anyone advise me which of the four wires (Red, Black, Orange, Grey) go to which of the four locations on the decoder socket (L1, L2, L-, R+).

 

Thanks, Mike

 

[Nigelcliffe]

You've omitted "MO+" and "MO-" from the upper photo as probably relevant.  

 

How to do this ?    Multimeter and a diagram showing the 21pin pin-out (lots of those on internet).   Identify which pin is the track input (two of them) and see which solder pads connect.  Work round all you need - pickups, motor, etc,  making notes as you go.  

 

Note on the upper photo that L1 and L2 have a component marked on the board.  So, its possible that only one side of that component connects to the socket.     (Component likely to be either a resistor or an inductive coil, depends on the purpose). 

[peterfgf]

This appears to be a standard Bachmann 21-pin mounting plate.

My annotated diagram (attached) suggests the following (as a starting poin):

L1 and L2 are the motor pins

L- and  R+ are the track pins

Don't worry about other pins.  These are for fitting the DC noise supression resistors and capacitors.

The two larg solder tabs sticking out at one side are for the speaker (SP+ and SP-).

If you are not intending to swop tenders, then the wiring of the connection between loco and tender is up to you, so long as both sides are consistent.  I have standardised on Motor/Track/Track/Motor and then it doesn't matter too much.  Polarity is swopped around without a problem.

I hope this helps.

Peterfgf

[MikeCW]

51 minutes ago, peterfgf said:

This appears to be a standard Bachmann 21-pin mounting plate.

My annotated diagram (attached) suggests the following (as a starting poin):

L1 and L2 are the motor pins

L- and  R+ are the track pins

Don't worry about other pins.  These are for fitting the DC noise supression resistors and capacitors.

The two larg solder tabs sticking out at one side are for the speaker (SP+ and SP-).

If you are not intending to swop tenders, then the wiring of the connection between loco and tender is up to you, so long as both sides are consistent.  I have standardised on Motor/Track/Track/Motor and then it doesn't matter too much.  Polarity is swopped around without a problem.

I hope this helps.

Peterfgf

Thank you Peter.  Your diagram makes it all crystal clear. I could perhaps have got there myself with a meter and 21 pin diagram as suggested by Nigel but (a) I thought that someone would have the answer for me already and (b) I wanted to take a low risk approach, avoiding any chance of blowing an expensive sound decoder.

The 0-8-0 should now be back "in steam" tomorrow.

Mike

[MikeCW]

2 hours ago, Nigelcliffe said:

You've omitted "MO+" and "MO-" from the upper photo as probably relevant.  

 

How to do this ?    Multimeter and a diagram showing the 21pin pin-out (lots of those on internet).   Identify which pin is the track input (two of them) and see which solder pads connect.  Work round all you need - pickups, motor, etc,  making notes as you go.  

 

Note on the upper photo that L1 and L2 have a component marked on the board.  So, its possible that only one side of that component connects to the socket.     (Component likely to be either a resistor or an inductive coil, depends on the purpose). 

Thank you Nigel.  Of course I should have thought of the 21 pin diagram and worked from there with my meter.  But now Peter has provided the solution for me and I'll get the decoder reconnected in the morning.

 

Mike