Early Diesels and decoders

[robinrick57]

I am working thru my 1965 era BR locos and adding decoders. Bachmann and Hornby steam locos all working satisfactorily or better. But I have Bachmann diesels, a 25 and a couple of 20's that wont play after adding decoders. I also have a Peak and I''m now thinking that will be the same. They all date from 2002 (ish) and have 8 pin sockets. With Digitrax DN136PS installed (I'm in the US) they start really slow, then suddenly speed up, and then wont stop. Is there a simple answer (I'm not electronically literate....born in Nottingham ). Thanks for any help in advance.

MOD NOTE... Topic moved to the DCC forum area where it should receive more views and replies.

[Flashbang]

Check CV3 acceleration rate. Set it to 1 or 2 and test if it was higher, then If that fails try it with DC operation turned off via CV29 - Read CV29 current value (If possible) and then add four to that read, e.g. if 2 or 34 make CV29 a value of 6 or 38 etc.
This CV29 calculator is handy to bookmark (Even though its the 2mm Association, it applies to all decoders regardless of scale) http://www.2mm.org.uk/articles/cv29%20calculator.htm

[robinrick57]

Thanks Flashbang. Yes I've looked at the acceleration rates and also reset the decoder to factory settings, even though they were never altered. No change in loco behavior.

I think this does belong in the Bachmann section because I don't think its the decoders per sec. It seems to me it some weird combination of locos/motor AND decoder. I have 5 other locos with this same decoder and they all work as they should. BOTH 20's and the 25 all exhibit the same erratic behavior. I read older motors can draw more amps than more recent ones and this can be a problem. These erratic locos all work fine using a DC transformer/test track.

[SRman]

I have two suggestions:

1. Remove any capacitors on the motors. This can be tricky with the Bachmann can motors as the caps can be hidden at the bottom of the motor. In my experience, there are usually three capacitors in Bachmann's diesel models.

2. Try a different brand of decoder. I have had no problems at all in Bachmann diesels (including several class 20, 24 and 25 models) using ESU, Zimo or Lenz decoders.

To be honest, I am not a fan of Digitrax decoders. I still have a few in use but when they fail, I replace them with something else. In the case of my Bachmann N class 2-6-0 steam locos, the Digitrax decoders were hard-wired in, but I have slowly replaced these older decoders with TCS M1 decoders, which are small enough to fit in the very limited space in the N class firebox. Any plug-in ones have long ago been replaced.

[Peterm]

Horses for courses I suppose, but I don't like Digitrax or TCS decoders. Lenz are good and I used to use them, but I've standardised on Zimo now for both sound and non sound. I had a DIgitrax (DH123 I think) and have had a couple of TCS and these showed the symptoms that you're describing.

[Bigmet]

1. Remove any capacitors on the motors. This can be tricky with the Bachmann can motors as the caps can be hidden at the bottom of the motor. In my experience, there are usually three capacitors in Bachmann's diesel models.

2. Try a different brand of decoder. I have had no problems at all in Bachmann diesels (including several class 20, 24 and 25 models) using ESU, Zimo or Lenz decoders...

Couldn't agree more with the above.

Because the Bachmann centre motor design is such an easy mechanism to drive, I first used the Bachmann badged ESU lokpilots v1 sold as 36-533 and 36-534 as these were the lowest cost decent decoder at the time: but it was essential to snip out the capacitors to eliminate 'effects' such as the OP describes. (Later I moved to the Lenz Standard as that was price competitive when introduced and a much superior decoder, and there's no necessity to remove capacitors.)

With the body off, on most of their mechanism designs there's gaps at the side of the motor allowing access for a small wire cutter, so that at least one lead on each capacitor can be cut through to isolate them. That's the quick, cheap and dirty method ,and has been trouble free on all the Bachmann diesels I have DCC fitted in the last 18 years.

[robinrick57]

Thanks for the help guys. I get what you are saying about decoders. in Europe everyone that knows anything recommends Lenz and/or Zimo. I've used Digitrax for years on my US 'train set' and never had a problem. They are the most available product. Must have installed (OK plugged in) over 50. That's why my logic (not actual knowledge) was telling me the locomotives must be part of my issues. I think some older 'DCC ready' US outline locos had issues with capacitors. Now my electrical naivety kicks in..... is the yellow blob, marked C1 in the photo a capacitor? Do the others look like that?

[Ironduke]

C1 is a capacitor
L1 and L2 are inductors

All of these components may adversely affect the PWM output of a decoder. I'd be inclined to remove the board entirely and hard-wire the decoder if it was mine.

[Peterm]

When you remove the inductors replace them with wire links or you'll get nothing.

[Bigmet]

...is the yellow blob, marked C1 in the photo a capacitor? Do the others look like that?

It is, and the ones attached directly to the motor are of similar appearance on all the Bach OO twin bogie models I have seen.

The aperture in the grey block just above the fuel tank moulding should allow you to see them.

[robinrick57]

Again thanks for all the help guys. Down and dirty (Bigmet) would suit me just fine but I cannot see anything that looks like a capacitor in that gap. I also cannot figure out how to move the big grey block away from the black chassis frame to get a better look or hardwire. I think I have all the screws removed. Its tricky when there are no guidelines and you are quite likely to brake something if you use too much pressure. I looked, and failed, to find much in the way of Lenz or Zimo decoders this side of the Atlantic. Kernow looks like a good bet in the UK, and they also seem to have good inventory of Bachmann rolling stock so I'll probably get a couple next order.

[End2end]

Kernow looks like a good bet in the UK, and they also seem to have good inventory of Bachmann rolling stock so I'll probably get a couple next order.

Don't forget they now have 2 stores so if it's not in stock in one it may be in their other.
Thanks
End2end

[Ironduke]

I looked, and failed, to find much in the way of Lenz or Zimo decoders this side of the Atlantic.

DCCSupply for Lenz
sbs4dcc for Zimo

[Peterm]

Again thanks for all the help guys. Down and dirty (Bigmet) would suit me just fine but I cannot see anything that looks like a capacitor in that gap. I also cannot figure out how to move the big grey block away from the black chassis frame to get a better look or hardwire. I think I have all the screws removed. Its tricky when there are no guidelines and you are quite likely to brake something if you use too much pressure. I looked, and failed, to find much in the way of Lenz or Zimo decoders this side of the Atlantic. Kernow looks like a good bet in the UK, and they also seem to have good inventory of Bachmann rolling stock so I'll probably get a couple next order.

Google 'foothill models' they used to be OK for Lenz decoders, or Digitrains in Lincoln (UK) for Zimo. I would have thought you could get the Zimo's over there though.
Edit to put this on: https://store.sbs4dcc.com/ZimoDCC-3.aspx
I found loads of places in the US.