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Author Topic: Dummy plugs  (Read 2285 times)
darby

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« on: June 11, 2009, 09:45:49 PM »

Can someone please tell me what the dummy plugs that came with my new
DCC train are for and why would I need to use them?
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pdlethbridge
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« Reply #1 on: June 11, 2009, 09:52:11 PM »

Those would be if you wanted to remove the decoder. Those would be installed where the decoder was removed so you could run on regular DC, not DCC.
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darby

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« Reply #2 on: June 11, 2009, 10:18:40 PM »

Thankyou. That was fast and just the info I was hoping for. I am new to this hobby and grateful to you.
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Pacific Northern


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« Reply #3 on: June 13, 2009, 04:11:46 PM »

The Bachmann DCC equipped engines will run on eitherr DC or DCC, the decoder senses what type of power is being used and reacts accordingly.

That being said, you can run the engine on DC power without taking the decoder out and installing the dummy plugs.

When would it be advised to take out the decoder and install the dummy plug?
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Pacific Northern
Yampa Bob

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« Reply #4 on: June 13, 2009, 04:32:20 PM »

Some claim, or have reported, that running on DC with the decoder installed requires a higher throttle setting to start, and/or results in erratic speeds.

If someone runs strictly DC power, then it probably would be practical to remove a non-sound decoder as it serves no purpose.

In case of a decoder failure running on DCC, I suppose you could install the dummy plug/pins so you could temporarily run the locomotive as an analog unit.

It does make a case for plug in decoders as opposed to hard wired.

« Last Edit: June 13, 2009, 04:37:13 PM by Yampa Bob » Logged

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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #5 on: June 13, 2009, 06:16:20 PM »

When would it be advised to take out the decoder and install the dummy plug?

When you double head with a similar locomotive that has no decoder.

However, you usually do not have to remove the decoder unless it has an integral plug.  If the plug is on the end of a bundle of wires, just unplug it and put the dummy plug in its place.  That way your decoder is safe and available when you want to convert back.

Jim 
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Atlantic Central

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« Reply #6 on: June 18, 2009, 08:33:51 AM »

The Bachmann DCC equipped engines will run on eitherr DC or DCC, the decoder senses what type of power is being used and reacts accordingly.

That being said, you can run the engine on DC power without taking the decoder out and installing the dummy plugs.

When would it be advised to take out the decoder and install the dummy plug?

There are a number of DC throttle designs that are not truely compatible with many dual mode DCC decoders. So some people will find their dual mode decoder equiped locos run very poorly on their very nice DC throttles.

Example: I use the Aristo Craft Train Engineer wireless throttle. Many dual mode decoders, like those in the newest run of Bachmann GE 70 tonners, simply will not work with my throttles. The loco hums loudly, sputters, tries to run, but has basicly no speed control.

Regular DC locomotives, old or new, run exceptionaly well on the Train Engineer throttle, with slow speeds and smooth performance as good or better than DCC.

Other locos with dual mode decoders work OK, but its just OK. They run much better with the decoders removed. I remove all DCC decoders from the few locos I buy that way and give them to my DCC friends.

On any kind of DC throttle, even the very best dual mode decoders offer only fair perfomance. The high starting voltages alone make slow starts and fine control dificult. I tested several new DCC equiped Spectrum 2-8-0's on a good MRC pack at my workbench test track and with my wireless throttles. On both types of throttle, they ran much better with the decoders removed.

DCC designers and manufacturers have no real vested interest in DC compatiblity. In fact I'm sure they hope you are unhappy enough with the performance that you invest in a DCC system.

Thank you Bachmann for the jumpers!

Sheldon
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #7 on: June 18, 2009, 01:04:32 PM »

Nobody in the electronics world would refer to the output of a Train Engineer as dc.  At low throttle settings, it is intermittent pulses with nothing in between.  If it were not for the physical inertia of the motors and their flywheels, dc only locomotives would not run smoothly on this waveform either.  The big advantage of this Pulse Width Control is that the voltage is high enough to turn on lights, even at low throttle settings.  If the lights are LEDs, they briefly flash on at near full brightness with each pulse and the visual persistence of your eyes (their "optical inertia") makes the light seem continuous.

Enter the decoder.  To work properly, the electronics in a decoder needs a steady supply of electricity.  To work during the transition time of DCC rectangular waves and during the brief time that full wave rectified 60 cycles is at zero, the manufacturer includes some "electronic inertia" in the form of a capacitor.  But the length of time the physically and electrically small capacitor can power the decoder is very short.  If it is shorter in a particular decoder than the time between the pulses received from the track, then the decoder will have to restart every time a new pulse comes along.  Is this confusing?  Certainly to the decoder it is.

What is the solution?  Off the top of my head, I would say installing a larger capacitor in the decoder might work (or it might not.)  Installing some electronics between the output of the Train Engineer and the tracks to convert the pulses into dc would work but would be expensive if, as I suspect, there is no commercial circuitry to do this.  Replacing the Train Engineer with a radio system that outputs dc (if there is such a system) would also be expensive.  Bottom line, I think you are already using the best solution - bypass the decoders you can, remove the decoders you can't.  No cost beyond your time.

Jim

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Atlantic Central

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« Reply #8 on: June 18, 2009, 04:00:50 PM »

Jim,

I have no problems with what I am doing, and have no interest in retaining the decoders. I was just pointing out to other readers things they might need to know about dual mode decoders.

The Train Engineer does have a "linear" mode, which I suspect is just a big capacitor across the outputs. The dual mode decoders perform only slightly better with the TE in linear mode. The TE is far from being the only pulse width throttle out there, in fact most of the new development in DC throttles has been with pulse width modulation.

The TE constant lighting effects are very good.

And, as I mentiioned, I have tested a number of dual mode decoders on other more "conventional" DC throttles. Their DC performance is poor at best in my opinion, even on pure DC.

Sheldon
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