Frates Posted January 10, 2014 Share Posted January 10, 2014 Hi chaps I wonder if someone could offer some insight into a problem I'm having with a newly acquired Bachmann 4MT standard tank. Unfortunately the performance is terrible - it jerks around on the layout, especially at low power, the inertia is all wrong so that sometimes it starts / stops quickly and other times it violently shudders or keeps running right into the buffers. Its smoother when I run at higher power but I only have a short layout so its mainly needed for slow speed duties. I've tried running it DC and it runs nice and smoothly even at very low speed. It came factory fitted with a Bachmann decoder which I tested in my one other loco (A Heljan Western), and it runs perfectly, so I guess that rules the decoder out. Likewise I've tried the decoder from the western (a Hornby 3 function) in the 4MT and I get the same erratic behavior. Does this confirm the problem lies with the 4MT itself? I'm pretty new to DCC so I don't know exactly what to look for but I've had a good look inside the loco and and I can't see any problems with bad wiring, soldering, etc - it all looks clean and tidy. My DCC controller is one of the older Bachmann EZ command's (the light grey one) so maybe that's the problem, I don't know? I've tested it on a single piece of flexy track to make sure its getting enough power / signal and I get the same poor performance as on the layout. Any advice would be much appreciated! Thanks, Frates Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted January 10, 2014 Share Posted January 10, 2014 Is this the Bachmann 36-553 decoder? If so, these need adjustment to the values in CV's 54 and 55 to optimise BEMF for the small motor. (The default values run larger motors with flywheels - such as those in centre motor both bogies driven chassis like your Heljan Western - very well.) There are suggested values to experiment around on the Bachmann site here. http://www.Bachmann.co.uk/pdfs/decoder_settings.pdf Cutting out the capacitors is usually helpful too. Personally I would say get yourself a Lenz Standard for the 4MTT, it will run it beautifully on factory default settings. Link to post Share on other sites More sharing options...
RMweb Premium Neal Ball Posted January 10, 2014 RMweb Premium Share Posted January 10, 2014 Thats a great reply, my normal reaction would be "faulty decoder" By and large I don't change the default CV settings, looks like I should! Link to post Share on other sites More sharing options...
Frates Posted January 10, 2014 Author Share Posted January 10, 2014 It is the Bachmann 36-553 yeah. But it was a factory fitted decoder - so it seems odd that they can ship it out with default CV values that don't work for the stock motor! It's also strange that the Hornby decoder gives the same poor performance? Unless, as you mention above, the Hornby is also not optimized for this particular loco. My other problem of course, is that my EZ command controller cant program CVs - so it looks like my first option will be to try a new decoder. Thanks! Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted January 10, 2014 RMweb Gold Share Posted January 10, 2014 Is this the Bachmann 36-553 decoder? If so, these need adjustment to the values in CV's 54 and 55 to optimise BEMF for the small motor. (The default values run larger motors with flywheels - such as those in centre motor both bogies driven chassis like your Heljan Western - very well.) There are suggested values to experiment around on the Bachmann site here. http://www.Bachmann.co.uk/pdfs/decoder_settings.pdf Cutting out the capacitors is usually helpful too. Personally I would say get yourself a Lenz Standard for the 4MTT, it will run it beautifully on factory default settings. This is the answer. Andi Link to post Share on other sites More sharing options...
Frates Posted January 11, 2014 Author Share Posted January 11, 2014 That did it! I take it from the big red writing this may have been a common thing, so apologies if its been done to death! But I'm over the moon its up and running. Thanks all! Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted January 11, 2014 RMweb Gold Share Posted January 11, 2014 It is a very common problem and far too many people are still trying to argue that it is not the answer when it has been proven time and again to be the solution. I've seen a loco go from kangaroo to tortoise in seconds by three quick component snips, as you have proved. One more for the evidence pile Andi Link to post Share on other sites More sharing options...
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