# Help with MRC Control Master 20



## igs59 (Jan 25, 2020)

I was given a Control master 20 - not sure if it works - plugged it in and only get voltage across terminals labeled for meter purposed terminals 3,4. No voltage across any other terminals - no manual and cannot find one online. I have tried different settings to same results. ANy ideas how I can proceed? New to trains and would love if this works for now.


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## Tom_C (Jan 8, 2016)

This manual seems pretty limited:

https://www.horizonhobby.com/pdf/MRCAA444.pdf


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## igs59 (Jan 25, 2020)

Thanks for PDF any Ideas how to Proceed?


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## Tom_C (Jan 8, 2016)

Not really. A 30 second skim of the manual say terminals 1-2 are for a volt meter, 3-4 for an ampmeter. Obviously the Track DC goes to the track, AC out is 16VAC for accessory power, and that should have 16v when the power is turned on.

The Track power should vary with the control (show a picture of the control unit).

That's about all I can tell you. It doesn't appear to be that complicated, so it should be easy to test.

Also, you want to keep it in the HO position unless you're running G scale trains. Nudge gives you better granular control at low speed.
If you aren't getting any power out, check for fuses or circuit breakers.


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## Lemonhawk (Sep 24, 2013)

If terminals 3-4 are for an ammeter, then they might have to have a short across them to get anything to work - If you don't connect an actual ammeter. That's probably why you only get a voltage across 3 and 4.


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## Tom_C (Jan 8, 2016)

igs59 said:


> plugged it in and only get voltage across terminals labeled for meter purposed terminals 3,4. No voltage across any other terminals


Sounds like he got a voltage across 3-4. I didn't read all the manual, but I *assume* that you don't need to use terminals 1-4 unless you want to. Not sure though.


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## Lemonhawk (Sep 24, 2013)

Yes if you read the manual it talks about a shunt bar across terminals 3 and 4 if no ammeter is connected. Not sure if the shunt is internal or external and missing, but without the shunt, you will get no voltage to the track. If you do use an ammeter then you need to remove the shunt. Adding your own shunt (just a piece of 18, or higher gauge piece of wire across terminals 3 and 4 will act as a shunt and won't effect anything even if there is an internal shunt.


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## Tom_C (Jan 8, 2016)

Ah. A little RTFM will go a long way.


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## igs59 (Jan 25, 2020)

*Working - closed*

Thanks all - the shunt got it work _ appreciate the timely helpful:smilie_daumenpos: responses


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