Bachmann 4MT Standard pick up wiring?

[philsandy]

Can anyone confirm the wiring connections to the pick ups on a Bachmann 4MT Standard 2-6-0.

 

I have bought this new, and whilst converting it to EM two of the wires came away from the pick up strip (like they always do. And I thought I was bad at soldering!)

I re soldered them and also soldered a black wire to each strip for additional pick ups on the front pony wheels  at a later stage.

Tested, and the loco ran fine on DC.

When I fitted the decoder it would not run, at first I thought I had a faulty new decoder, but have since confirmed it is not, and the fault is with the loco, and I have done something wrong when re soldering the 2 loose wires.

I have several Bachmann locos but never seen one wired like this.

 

A red and black wire from the motor that are both soldered on the same side (LH).

I also noted that the LH & RH strips appear to be connected??

At the other end, 4 wires from the decoder socket, a red and orange soldered to the LH side, and a black and yellow wire that came loose, I just soldered these back on to the 2 blobs of solder on the strip, that were on the RH side. I can not be sure that this is where they were originally, but can not see where else they could go.

Please can anyone enlighten me? 

[34theletterbetweenB&D]

Curiosity being my middle name, I just had to go and take a look inside mine, which uncharacteristically I had never yet had in pieces.

 

The basic answer to your question is that it is wired unlike most Bach steamers I have tinkered with. The purpose is to route the wiring fully concealed between socket and motor. This is achieved as follows:

 

The pick up wiper strips exactly as usual are connected to red and black which go to the decoder socket, nothing strange there.

 

The orange and grey from the decoder socket are then routed to the motor via the keeper plate. That's why it looks so confusing!

 

Didn't completely strip the keeper plate assembly off the loco to see exactly how the orange and grey conductor routing is arranged in the keeper plate, but it looks to me like a couple more copper coloured strips are in there, which must both be insulated from the pick up wiper strips.

 

I feel from where you are at present my choice would be detaching all the wires from the keeper plate, and then determining with the keeper plate independent of the loco exactly what connects to what and that all four conducting strips in the keeper plate are fully insulated from each other, and then restoring the connections one by one. This because almost certainly one of the motor supply strips has become connected to a pick up strip, and that needs to be rectified first: pretty confident of this because it matches your symptom of a loco that runs perfectly on DC, but is unable to be operated on DCC.

[philsandy]

34C many thanks for your reply, most helpful.

Have sorted the problem, I had soldered the yellow and black wires to the wrong terminals, they just needed switching round.

I thought it might be that, but then dismissed it because with both these wires being on the same pick up strip, the RH side, that it would not make any difference.

But as you say:

"but it looks to me like a couple more copper coloured strips are in there, which must both be insulated from the pick up wiper strips".

 

and that is exactly the case.

I'm not good at electrics, and this unusual wiring arrangement really threw me.

Anyway, as soon as the wires were swapped round it worked.

It ran pretty rough until I snipped the caps and now runs superb, I've never seen such a vast improvement after doing this, and I have not yet had to alter any CV's.

 

Thanks again.

[34theletterbetweenB&D]

Glad that worked out. Slightly curious why they designed it that way, when the scheme used on the 9F solves the same problem more elegantly, is a whole lot easier to separate body from mechanism, and simpler for most dismantling and repair jobs.

[Butler Henderson]

Its one thing to check when fitting a decoder if it shows up an error on the programming track. Was really puzzled until I noticed a slightly bigger than normal solder blob - the wire fixed to one the pickup strips had a solder blob big enough to contact onto the adjacent motor strip. Not a problem on DC but obviously a major problem for DCC.