040 locos to DCC including Smokey Joe

[Howhoward7]

I recently converted a new Smokey Joe to DCC following the on line instructions during this I noted that the so called RED capacitor looked more like a wire wound resister. I have since some very old 040 units that do not have this component. Is this a

 

current limiting resistor and if so is it really needed? If so does know its resistance and power rating.

 

Thanks

 

Howard

[Fishmanoz]

Howard, I think you'll find it is a black capacitor. I agree it looks a little like a resistor but they should have coloured rings being code for their resistance value or have the value stamped on them, but goodness knows how the Chinese may do it.

 

You

 

might also look at my reply 33 days ago in Hornby Collectors Club forum titled Collector loco (it's on page 2 there) where I give detail about how the actual process for fitting chips to the latest Collector 0-4-0s is different from the instructions on the

 

web site - includes that the red capacitor is black. I think the web site may be a little out of date with current manufacture.

 

Maybe HCC should check this to see if the web site should be updated?

[Fishmanoz]

You could check it with a multimeter - it will show open circuit if it is a capacitor (capacitors are open circuit to DC and decrease in impedance as the frequency rises through them and in this case, impedance can be read as resistance - yes I know about

 

the -ve 90 degree phase shift).

[Howhoward7]

Hi Fishmanoz

 

Thanks for that. I noticed that it was black not red and I didn't bother checking for a value cos I wasn't expecting to do any more of them! If it's a cap, which it probably is, would not having it cause interference to the DCC controller

 

or other locos running at the same time?

 

Howard

[Fishmanoz]

Hadn't really thought about it, just installed the chip and noticed how far out the instructions were - the 2nd one was much easier as I'd already pulled the motor out for the first and that wasn't necessary. But it's unusual, the red/black capacitor is

 

in series with the chip across the pickups and that component is not part of a "standard" configuration. It makes it open circuit to DC but has a small resistance at AC. All DCC feed is AC made up of DCC control instructions coded to each loco plus the power

 

feed (AC too). Take a look at the DCC part of the Brian Lambert site for a good explanation.

 

Not sure why the cap is needed for this loco type though as it's not needed for others. I could speculate it's like an AC equivalent dropper resistor as not

 

so much power is needed by the small loco motor. Don't think it's an interference issue though? Maybe someone else has an idea?

 

John

[Blackbird]

Components used in DC model locos; a capacitor, connected 'across' the motor supply, to suppress RF interference (it reduces HF voltage transients caused by motor slipring 'sparking'). Inductors, connected in 'series', (look like resistors) are also employed

 

to supress RF interference by smoothing the current flow.

Most DCC decoders have this RF suppression incorporated, so additional components are not required. However, as these suppression facilities are fitted to the output of the decoder (to the motor),

 

they will have no effect to the input, and can't corrupt the DCC signal. They will, however, have an effect on the back EMF output received by the decoder and should be removed if 'Back EMF' decoders are employed..

[ace10086]

Blackbird said:
They will, however, have an effect on the back EMF output received by the decoder and should be removed if 'Back EMF' decoders are employed..

Just to add, both of Hornby's current DCC decoders use Back EMF.

[Fishmanoz]

blackbird, understand the suppression capacitor in parallel across the output and motor. The red black Cap in question though is in series with the input coming off one of the track pickups - see the instructions for fitting decodes to 0-4-0s on this site

[ace10086]

just had a look at my 0-4-0. Cut away some of the insulation on the RED capacitor (in my case black), it is a choke not a capacitor. In theory it should be needed, however I left mine in place and it runs fine - well as fine as these models do.

 

Not

 

sure why the Hornby instructions tell you to put the normal capacitors back on the motor! If you go to all the trouble of unsoldering them you certainly don't want to be putting them back on.

[Fishmanoz]

So that would seem to have interference suppression as its purpose, a choke in series doing much the same job as a capacitor in parallel.

[Glenn c]

Can anyone help me can a sound decoder be fitted to smokey joe 

[jane1707819582]

Can anyone help me can a sound decoder be fitted to smokey joe 

Yes ,the only restriction is space.you will need a small speaker .

[96RAF]

It will not be a simple plug and play out of the packet. You are going to have to have reasonable modelling skills.

 

People have sound in N gauge so almost anything is possible in OO.

[Fishmanoz]

Well done with your search skills pulling up this 7 year old thread!  And at the same time showing me up for not instantly recognizing the series component as an inductor!  At least I've learnt something in 7 years.

 

Which is more than I can say for Hornby,  After 7 years, the 0-4-0 instruction guide is still wrong.  It assumes the motor is mounted connector side down so has to be removed to unsolder the pickup wires and connect the decoder wires. It's actually mounted connectors up so doesn't have to be removed.  And while they have to say re-install one of the capacitors, this also isn't necessary.