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Discussion Starter · #1 ·
Hello this is the first time i have used a forum please be gental with me. I have fitted a bachmann 3 function chip to a Hornby class 66 but when i move to the first speed step the loco jumps, spluters,stops & starts until you speed up after that is seems ok. I have some knowledge dcc but this has me stumped. cheers. Andy
 

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Im assuming that the loco and track are clean and is this the only chipped loco on your track,(Im not an expert,just trying to be helpfull)
 

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QUOTE (frame69 @ 6 Feb 2009, 18:02) <{POST_SNAPBACK}>Im assuming that the loco and track are clean and is this the only chipped loco on your track,(Im not an expert,just trying to be helpfull)


Provided the above is in order & every pickup is working correctly the next thing to check is that you have removed all of the capacitors.

Once you have done that & still no joy then come back - let us know how you get on anyway.
 

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Discussion Starter · #4 ·
The loco is new runs ok in dc, and track is clean. not sure what the capacitors look like, don't want to snip away at something I don't understand.
 

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Capacitors are usually little brown components that look like tiny bags with two wires. Normally wired across the motor terminals.

The Class 66, if it has lights, might well have a full circuit board. Don't touch this unless you know which part of the board does what. Modern models are usually DCC ready and it is rarely necessary to change or snip components BUT capacitors are required to be fitted for anti suppression but are not needed for DCC, thus the advice to remove them. Early decoders such as the Bachmann one you are using are less able to cope with these capacitors. you might find that fitting a better decoder will cure the problem and give you a much better insight into the delights of DCC control.
 

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All my decoaders are Bachmann 3 function and they all worked well out of the box except the two fitted to Hornby locomotives. Settings relating to the motor controlthat needed changing were as follows :

CV2 Start voltage - set quite high, for me 5 was about right
CV3 Acceleration - low, down to 1
CV4 Retardation - low, down to 1
CV53 Feedback reference - set quite high, for me 50 seemed to work
CV54 Feedback parameter K, low, down to 12
CV55 Feedback parameter I, a bit high, for me 36

The hornby motors seem to have totally different characteristics to the Bachmann ones. I suppose it is only to be expected that Bachmann decoaders are set to suit Bachmann locomotives.

The above settings cured the eratic running. Removal of capacitors had no effect after getting the setting correct, I've now got one Hornby with and one without !

Hope this helps

Bob
 

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The Bachmann 3-function decoders that I used recently were in fact ESU (& stated as such in the instructions), so these should be able to cope with almost any motor that's operating correctly.
 

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*** The quality of the decoderhas no absolutely no relationship to the simple fact that the capacitors interfere with the communication between the decoder and the locomotive. The bachmann decoder is a reasonable quality one anyway being ex ESU.

Bachmann loco's are very susceptible to the interference, and removal of the caps will definatley fix the problem.

Bachmann usually solder in more than one - look at the motor - if there is anything soldered to the motor case and motor brush other than the wire that is needed, it will be a capacitor - remove it (them) totally and make sure that there is only a single wire to each brush holder.

If you cannot locate the caps I'll be surprised - they are a pale biscuit colour usually and a flat disc a few MM across... they should simply be snipped out.

regards

Richard

QUOTE (dwhite4dcc @ 7 Feb 2009, 06:56) <{POST_SNAPBACK}>Capacitors are usually little brown components that look like tiny bags with two wires. Normally wired across the motor terminals.

The Class 66, if it has lights, might well have a full circuit board. Don't touch this unless you know which part of the board does what. Modern models are usually DCC ready and it is rarely necessary to change or snip components BUT capacitors are required to be fitted for anti suppression but are not needed for DCC, thus the advice to remove them. Early decoders such as the Bachmann one you are using are less able to cope with these capacitors. you might find that fitting a better decoder will cure the problem and give you a much better insight into the delights of DCC control.
 

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*** Actually the capacitors always have an effect, 100% of the time. They mask the back emf information from the motor and should be removed.

In reality, you just cannot see it as you trimmed CV2. A loco should crawl with CV2 set to 0 and no real changes to anything including back EMF if the communication between decoder and loco is right - and that means no caps.

Re your settings, neither CV2, 3 or 4 really have any effect on this relationship - they are simply running adjustments for start voltage and momentum.

ALL your improvement is due to CV53/4/5, and none of these would have been needed at all if the caps had simply been snipped.

Regards

Richard

QUOTE (BobB @ 7 Feb 2009, 15:36) <{POST_SNAPBACK}>All my decoaders are Bachmann 3 function and they all worked well out of the box except the two fitted to Hornby locomotives. Settings relating to the motor controlthat needed changing were as follows :

CV2 Start voltage - set quite high, for me 5 was about right
CV3 Acceleration - low, down to 1
CV4 Retardation - low, down to 1
CV53 Feedback reference - set quite high, for me 50 seemed to work
CV54 Feedback parameter K, low, down to 12
CV55 Feedback parameter I, a bit high, for me 36

The hornby motors seem to have totally different characteristics to the Bachmann ones. I suppose it is only to be expected that Bachmann decoaders are set to suit Bachmann locomotives.

The above settings cured the eratic running. Removal of capacitors had no effect after getting the setting correct, I've now got one Hornby with and one without !

Hope this helps

Bob
 

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Discussion Starter · #10 ·
Hi gents THANKYOU for your input on this little problem, the cv settings BobB submited work! The loco craws along beautifully Thanks Bob, I have made a note about the caps and will try this on a different loco if the problem occurs again. I'm sure I will have more questions and problems as I journey into the world of DCC.
Thankyou all again cheers Andy.
 
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