Fitting DCC to Bachmann Farish N scale 08 "Basra"

[Ian Morgan]

I have just fitted a DCC decoder into a Bachmann Farish N scale 08 "Basra" for a friend. This recent 'Collectors' model is not DCC ready, so I thought I would show how I did it here.

 

First remove the body by removing 4 very small screws hidden away below the footplate. A pipe by the front left footsteps needs to be moved out and onto the footplate.

 

Next, remove the weight/cover from above the worm, which is held by a single screw.

 

 

Note the black wire is solder to a tag here. This wire will be replaced later.

 

 

The trickiest bit was unclipping the motor from the chassis, by gently levering open the plastic clips each side.

 

 

When the motor is free, you will find a phosphor-bronze contact strip below the motor. A tag at one end makes contact with one of the motor pins that is soldered to the PCB and filed flat. I folded this tag the other way and will refit it so it will be on the other side away from either motor pin. I will then solder the red wire from the decoder to it.

 

 

The PCB needs to be removed and discarded. It is soldered to the two motor pins. Desoldering braid or wick is used to remove solder and free the PCB.

 

 

With the PCB removed, the two motor pins can be seen.

 

 

Now assembly can start. There is not much room above the motor inside the body, so a very thin decoder is needed. I fitted a Zimo MX621 decoder, but the MX616 should also fit, or anything 2.5mm or less, with a footprint less than 14mmx9mm should do. The thickest part of the MX621 is a capacitor that is slightly off-centre, so I fitted the decoder off-centre so the capacitor was central to the body where the gap is widest.

 

Kapton tape insulates the decoder from the motor and the metal body.

 

 

There are no lights, so just the red, black, orange and grey wires are needed. The black wire is soldered to the tag the original black wire was soldered to. The red wire is soldered to the reformed tag on the plate below the motor. The orange and grey wires go to the two motor pins.

 

 

Job done. Now I just need to adjust the CVs.

 

 

 

Edited January 24, 2021 by Ian Morgan
typos

[Ian Morgan]

And a quick video:

 

DCC fitted Basra by Ian M, on Flickr

 

[Steven B]

I used a CT Electronik DCX75 when I converted my 08:

https://flic.kr/s/aHsjwiAeB1

 

With care it's possible to do the conversion without removing the motor or PCB (likewise the 03, 04 and 14 which are converted in a similar way). The decoder fitted between the side of the bodyshell and motor.

 

@Ian Morgandid you find the MX621 simple to tune to the 08? I'm still not happy with my DCX75 installations but I'm not sure if it's down to not having spend enough time tuning the decoder or if there are electrical/mechanical problems that need addressing.

 

Steven B.

 

 

[Ian Morgan]

I am hoping to do the CV tuning this evening, so I will report back tomorrow,

 

Out of the box it runs OK, but is a bit 'grumbly' sounding. Also top speed is way too high.

 

Ian

[woodenhead]

16 minutes ago, Steven B said:

I used a CT Electronik DCX75 when I converted my 08:

https://flic.kr/s/aHsjwiAeB1

 

With care it's possible to do the conversion without removing the motor or PCB (likewise the 03, 04 and 14 which are converted in a similar way). The decoder fitted between the side of the bodyshell and motor.

 

@Ian Morgandid you find the MX621 simple to tune to the 08? I'm still not happy with my DCX75 installations but I'm not sure if it's down to not having spend enough time tuning the decoder or if there are electrical/mechanical problems that need addressing.

 

Steven B.

 

 

I've seen video of the lesser implementation which I hope to follow, that said the method in this thread does look neat when complete.

 

Edited January 25, 2021 by woodenhead

[Ian Morgan]

I notice the guy in the video does not remove the suppression capacitors from PCB. That may affect any back-emf feedback monitoring by the decoder, which will make smooth control of speed unpredictable. DCC does not require suppression capacitors.

 

@Steven B appears to have removed one capacitor, but does not mention it.

 

Edited January 25, 2021 by Ian Morgan
Worked out how to mention another member.

[Ian Morgan]

So I fired up DecoderPro and set the DCC address. I added a little inertia (5 for accelleration and 3 for decelleration) just to inhibit sudden starts and stops , but not enough to worry a novice driver. I also capped the top speed to something that feels prototypical.

 

I am not an expert in tuning CVs though, so that is as far as I can comfortably go. It is still a bit of a growler and slightly 'coggy' at slow speeds, but I don't know if tweaking CVs can fix that.

 

 

 

[woodenhead]

7 hours ago, Ian Morgan said:

I notice the guy in the video does not remove the suppression capacitors from PCB. That may affect any back-emf feedback monitoring by the decoder, which will make smooth control of speed unpredictable. DCC does not require suppression capacitors.

 

@Steven B appears to have removed one capacitor, but does not mention it.

 

In a later video he did make some CV changes to get the crawl to an absolute snail pace so it did seem controllable.

[Ian Morgan]

10 hours ago, woodenhead said:

In a later video he did make some CV changes to get the crawl to an absolute snail pace so it did seem controllable.

 

He has a lot of videos on his channel, but I could not see one with a title that hints it covers CV changes. Can you link to the one you mean, please?

 

 

[woodenhead]

1 hour ago, Ian Morgan said:

 

He has a lot of videos on his channel, but I could not see one with a title that hints it covers CV changes. Can you link to the one you mean, please?

 

 

Buried in his Shed Valley Railway videos, took me a bit too, I've set it to start at 9:05 where he begins talking about the 08: 

 

[Izzy]

I didn't realise there was enough room above the motor to fit a decoder there in these. Could this be transmitting sound through the body and giving the 'growly'? I have also stuffed a CTX DCX76 down the side of the chassis as they are so thin. Sadly all Zimo's are much fatter. I managed to fit a small tantalum SA pack in the nose to help things along. The settings I used were the defaults apart from setting cv3/4 to around the 30 mark. This is my basic level I use for all my locos, both CT and Zimo. I see the video install used a Lenz. Not surprised the slow speed wasn't as good, Lenz motor control is I feel a step or so down from CT/Zimo.