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Runaway train...

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  • Member since
    September, 2019
  • 1 posts
Runaway train...
Posted by jer630 on Saturday, September 14, 2019 5:20 PM

Hello...I am admittedly not an experienced railroader, but I recently broke out an engine and power pack from several years ago, bought some new track, and created a quick layout.  When I got everything hooked up (DC), the locomotive is either "full on" or "full off"...it won't respond to the speed control wheel on the power pack.  The only way to stop it is to turn it off.

I've worked with bad/dirty connections, but don't remember ever troubleshooting a train that won't respond...what could be a culprit for this?

HO scale

MRC 220 Power Pack

Right now just have wires from power pack going to one atlas terminal track.

 

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Posted by BigDaddy on Monday, September 16, 2019 11:35 AM

Welcome to the forum.  Your initial posts are moderated so your responses and maybe the above post take a while to appear. 

There is another similar thread, the MRC is the culprit

http://cs.trains.com/mrr/f/744/t/213998.aspx

Henry

COB Potomac & Northern

By the Chesapeake Bay

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Posted by RR_Mel on Monday, September 16, 2019 12:01 PM

You didn’t say what scale locomotive you’re running.  The MRC220 has a higher voltage out for G scale, 23 volts.  If you have a multimeter check the track voltage to see if the throttle changes the voltage.
 
It might be going down to round 5 or 6 volts and a low current can motor locomotive could still run at a pretty good clip.
 
 
Mel
 
 
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Posted by wvg_ca on Monday, September 16, 2019 1:04 PM

it might be something a simple as wrong connections ... they should go on the left .... the right is for accesories, and doesn't change with the throttle

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Posted by Alantrains on Monday, September 16, 2019 5:47 PM

Put a volt meter across the output terminals of the MRC220 and see if the voltage varies. That's what controls the speed of your train. It might help to put a 12volt bulb on the output. With the throttle turned to min speed the bulb should just glow and turning the throttle should increase the brightness. It sounds like the pot that controls the output has failed.

 

Alan Jones in Sunny Queensland (Oz)

 

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Posted by Redvdub1 on Tuesday, September 17, 2019 7:37 AM

We have had quite a few inquiries lately about MRC power packs but none re the 220 Tech IV pak (see the thread referenced in one of the responses to your inquiry.  I am pretty sure your problem is a shorted output Darlington transistor..probably a TIP 120 or near equivalent.  If there's only one output Tx you will have to replace it which is relatively simple to do.  If it's two Txs in parallel you probably only have to remove one of the two (unless both failed which is very unlikely).  Your biggest problem will be figuring out how to open the case because there are probably security screws which require security removal tools. I don't have a 220 at hand so I can't help you there.  The TechIIs all used #10 Torx security screws and a #10 torx security tool is readily available at HF or on the net.  The 1370 required a notched flat bladed screwdriver which I made with my dremel cut off wheel.  The old 2200 had odd ball screws which fortunately were not recessed so I could get a grab on them with some pliers.  Your case probably has two slightly recessed security screws and two deeply recessed security screws.  

Your 220 goes for around $70 per so it definitely is worth fixing IMHO.  I would be interested to hear what you find out if you do open the case and replace a Tx.  

 

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Posted by Midwest Northern R.R on Tuesday, September 17, 2019 8:19 AM

My answer depends on the voltage. My suggestion, simalar to all the others, is to use a multimeter to see if your voltage is varying, because that changes the speed of your locomotive. If your voltage is varying, than check that your power pack is running the correct scale. Most all of my Loco's run on 18.5-17 Volts DC, However, if your power pack is for a smaller scale, It may be putting out a larger amount of volts, thus making your loco run faster than regular operation.

  1. Check volts
  2. Check scale
  3. Check wiring
  4. Make appropriate repairs
  5. Try again

Try the steps listed above. Then tell us how it went.

P.s. In did some research on your MRC 220 Power pack, and somewhere it said it's meant for Z-Scale.

 

"Your never too tall to play with trains."

                                                          ~Liam

 

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Posted by richg1998 on Tuesday, September 17, 2019 11:12 AM

jer630

Hello...I am admittedly not an experienced railroader, but I recently broke out an engine and power pack from several years ago, bought some new track, and created a quick layout.  When I got everything hooked up (DC), the locomotive is either "full on" or "full off"...it won't respond to the speed control wheel on the power pack.  The only way to stop it is to turn it off.

I've worked with bad/dirty connections, but don't remember ever troubleshooting a train that won't respond...what could be a culprit for this?

HO scale

MRC 220 Power Pack

Right now just have wires from power pack going to one atlas terminal track.

 

 

Welcome.

With all the suggestions, you should be able to figure it out. Get back to us when you do. It might help someone in the future.

 

I tried to answer you last night but the site would not recognize my name and password.

Rich

If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.

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Posted by BroadwayLion on Tuesday, September 17, 2019 12:05 PM

I was going rto suggest the transformer, but here is another issue,

You may not havee connected your track to the track terminals, but rather to the auxiliary terminals.

 

Most acc outputs are AC in which your DC loco would just sit there and buzz. You might have a accc output in DC, or perhaps you aree running an AC rialroad on the acc cconnections.

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Posted by SPSOT fan on Tuesday, September 17, 2019 12:22 PM

BroadwayLion

Most acc outputs are AC in which your DC loco would just sit there and buzz. You might have a accc output in DC, or perhaps you aree running an AC rialroad on the acc cconnections.

Or you might have connected to the fixed DC instead of the variable DC! This would definitely cause the issue described by the OP! I don’t think fixed DC is ment to be used on locomotives!

I also once had a MRC Tech2 which would not make my engine stop at 0% throttle...

Regards, Isaac

I model my railroad and you model yours! I model my way and you model yours!

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