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SMust the Hornby non-motorised Mk3 DVT have a decoder fitted?

ColinB

1629 posts

Yes, you are absolutely right but they rely on diodes to do it, which is great on DC but on DCC they will probably switch the headlights on when you are going backwards, which is exactly what I said. Possibly they might flash on and off, I don't know. What I do know is that Hornby fitted that socket for a reason so they must think the same as me. This is effectively the same as a Pendolino or a Javelin, in both cases I have fitted a really cheap decoder to the dummy end which again is what I recommended.

Will Hay

135 posts

Virgin DVT set on fire...

 

https://www.hornby.com/uk-en/forum/post/view/topic_id/33995/?p=1

It takes strength to be gentle and kind.

Flashbang

1252 posts

If you remove the DC operation "Blanking plate" nothing at all will work, whether on DC or DCC! No lights or if its inside a loco, no motor controls.

The blanking plate plug allows a loco or unpowered carriage to work correctly on DC (Analogue) control.  Once its removed and its socket is left open there is no connection to anything!  

Replacing the blanking plug with a suitable decoder and on DCC power you can then adjust the decoder to allow lighting or motor (where a motor is fitted) operation to work at its best. 

Broken? It wasn't me. I never touched it!

Flashbang

1252 posts

As for the images of the burnt carriage, its impossible to say what caused this? But there are few possibilities...  Over heating decoder due to it having insufficient air flow - Its been wrapped in insulating tape or shrunk down heat shrink tubing.   The decoders components have over heated due a fault after the decoder.  The PCB of the carriage or loco has defective components or they have failed or have been subjected to an overload.  The decoder was installed incorrectly and a partial short circuit has become present allowing larger currents to flow causing overheating.  

 

But of course none of this will return the carriage or loco to its original condition.

But what should be learnt is that with DCC large currents can flow under fault conditions than ever seen with DC.   

Generally on DC the maximum current is around 1.0Amp on DCC this can be 4 or 5 Amps or more depending on the DCC system used. in the USA some DCC users will often have 10 Amp systems.   Consider this....Typical DC = 12 volts at 1.0 amp is equal to 12 watts.  On DCC 4 Amps at 15 volts is roughly 60watts, while 10Amps at 15 volts is 150Watts.  

60 watts is very hot.  Consider a conventional filament lamp rated at 60 watts. Its extremely hot! In fact don't touch such a lamp when lit, it will probably burn you!

Broken? It wasn't me. I never touched it!

Will Hay

135 posts

Hello.

The burnt out carriage you're looking at was used exactly as this one will be.

No decoder fitted, never opened, blanking plate never removed.

 

Hornby have been very good, I have to say.

Replaced without question, including my return postage costs.

It takes strength to be gentle and kind.

Fishmanoz

9868 posts

Might I give a simple summary of the 3 pages of hypotheses and conclusions to this simple original question and supplementary question (ignoring the burnt out item):

 

Must you fit a decoder to the non-motorized dummy car - No

 

What features do you miss out on by not fitting one - directional lighting that can be switched on and off on DCC

 

What do you get on DCC with the blanking plug fitted - lights on all the time.

 

What do you get on DCC without the blanking plug - no lights.

 

and thanks for all the fish

RAF96

14226 posts


Community Moderator

Compare these dummy cars with Pullmann coaches with lights. These are on all the time on dcc without any decoder fitted.

Halton Brat - Running Win 10, 64-bit - RM (Pro-Pack) with Elite as Controller-A, Select as Walkabout and E-Link as Controller-B - Locos are mostly TTS. http://www.halton96th.org.uk/robs_rails.html

ColinB

1629 posts

Pullmans have a different circuit. According to your last photo I saw, bridge rectifier, feeding capacitor with 5 volt regulator, so the lights remain at a constant level no matter the voltage (as long as it is above say 9 volt, about 2 volts across rectifier, 2 volts across regulator).Plus Pullmans don't have directional lighting for DC.

Fishmanoz summed it up exactly.

Will Hay

135 posts

Thanks to all.

It takes strength to be gentle and kind.

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