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Discussion Starter · #1 ·
Just had an interesting experience chipping my nice new Bachmann 45xx Small Prairie.
Fitted the chip which was a doddle as there is plenty of room, removed the caps, tested and after running a couple of feet, l was unable to change speed of loco, it stuck at original set speed. Tried in reverse with same result. In one instance, it even changed direction on it's own! I tried other locos, all worked fine. I then disabled analogue DC in CV29, still no change. After much head scratching, I thought that spikes must have been corrupting the DCC signal. I decided to refit suppression caps to loco, tested, ran like a dream. This definitely goes against the well-tested "remove capacitor" logic, but I'm happy
, it works. I'm using an MRC Prodigy Advance system, which I am very pleased with, also TCS M1 and T1 decoders, which I find very easy to set up.

Has anyone had experience of runaway locos? Comments very welcome.

Best regards
 

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Hi
That's a new one!

I wonder if somehow something wasnt quite correct when the loco was first chipped and after removing the body and fiddling around with the motor/caps etc the fault was removed without you knowing
 

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QUOTE (Howzatt @ 14 May 2007, 23:24) <{POST_SNAPBACK}>This definitely goes against the well-tested "remove capacitor" logic, but I'm happy
, it works.
There is no well-tested logic about removing capacitors, just a simplistic, increasingly pervasive dogma that removing them is the easy way out.
Each individual combination of decoder and loco/motor type ought be taken on its own merits by technical and/or practical means. The components were originally there for a reason, and a decoder does not necessarily replicate their actions, especially when you consider that most decoders are a considerable length of wire away from the motor.
 

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Discussion Starter · #5 ·
Thanks for the replies everyone, I think I've read somewhere a theory that decoders should take care of any voltage spikes that suppression caps normally soak up. Size for size, how any component on a tiny decoder board can do this same job beats me. Perhaps I am thinking too "analogue" here.
 

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QUOTE (Howzatt @ 15 May 2007, 22:21) <{POST_SNAPBACK}>
Thanks for the replies everyone, I think I've read somewhere a theory that decoders should take care of any voltage spikes that suppression caps normally soak up. Size for size, how any component on a tiny decoder board can do this same job beats me. Perhaps I am thinking too "analogue" here.
The problem with this theory is that the components on the decoder are usually a lot further away from the motor brushes than the directly mounted capacitors were, and what fills that gap is a piece of wire which can act as a transmitting antenna. It is most definitely an 'analogue' problem, with many variables, which is why most people choose the easy route of capacitor removal regardless of the potential side effects.
 

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From the ZTC website:-

QUOTE Q: Should I remove the EMC suppression components from my Locomotives?

A: We NEVER recommend the removal of the suppression circuitry.

First, it is illegal for us, or for that matter any other manufacturer to recommend the removal of a third parties EMS suppression devices. These components are fitted to ensure that the products do not interfere with TV`s and the like, which causes a nuisance and inconvenience. However this also includes some much more important items such as Pace Makers which are life critical.

Secondly, all of ZTC`s Decoders are designed to work with these components installed, as we believe are those produced by other manufactures, but only they can confirm this.

Thirdly, These components are also a necessary requirement to enable the various locomotive manufactures to obtain the obligatory EMC approvals. This testing permits them to print a CE mark on their products, which is also a legal requirement for all electrical equipment sold throughout the European Community.

In an effort to try and clarify this recurring confusion, ZTC Controls Ltd. formally tabled the question at the NMRA DCC working Group (of which other DCC manufactures and we are members) in September 2004 in Salzburg.

The question was "Does any manufacturer of DCC decoders recommend the removal of the locomotive suppression components when fitting a decoder in to a locomotive".
There were 30+ members present and not one said that they would, or do recommended their removal. The working group then minuted this fact.

This information was picked up, and later published on the Yahoo DCC web site by a qualified EMC Engineer, but the myth still seams to prevail that they should be removed.

Incidentally tests conducted by ZTC engineers indicate that many decoders properly installed, from a variety of manufactures including ourselves often do not work as well with these components removed.

Happy modelling
Gary
 

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I had exactly the same problems with the Hornby Pendolino. It would change direction and bolt off suddenly into the blue unprompted. My solution was to remove the decoder and replace it with a Lenz Gold. I then later also removed the capacitor. For the record there was no discernible difference after I removed the capacitor from what it was before.
 

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... because the Lenz decoder has built in suppression. Two layers of suppression are not needed and don't do anything extra.

There are more instances where removing capacitors that are required for use with DC make for better running under DCC than otherwise. Just ask anyone who has added a few dozen decoders to their locos.

It also depends on the manufacturer and type of decoder. Some have better suppression than others and perhaps some have none at all.

Follow manufacturers advice and if that doesn't work, pull the caps. If that doesn't work, put them back.

I don't know what all the fuss is about...
 

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QUOTE (Gary @ 24 Jul 2007, 04:36) <{POST_SNAPBACK}>From the ZTC website:-
Happy modelling
Gary

Gary,

ZTC may well say all of that, but the fact is, I have had quite a few locos, particularly Bachmann, which simply will not run properly without the suppression parts removed.

I believe that TCS decoders have suppression built in and can therefore have the same removed from the loco. TCS decoders definately do not work too well with Bachmann capacitors fitted!

Graham Plowman
 

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QUOTE The question (to the NMRA working group) was "Does any manufacturer of DCC decoders recommend the removal of the locomotive suppression components when fitting a decoder in to a locomotive".
There were 30+ (NMRA) members present and not one said that they would, or do recommended their removal. The working group then minuted this fact.

It is not a ZTC thing. It is an NMRA thing. If a capacitor is fitted to the loco prior to decoder installation then the decoder should be capable of functioning with the capacitor present. If it does not then it cannot comply with NMRA standards. The NMRA do not endorse the removal of CE EMU supression devices from locomotives.

Happy modelling
Gary
 
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