# Issue with MRC Power G



## alx19881 (Sep 23, 2017)

Hi all - 

Last year, I bought an MRC Power G transformer, which I have been using to run my LGB F7, as well as my two USA Trains F3 engines. Recently, I have noticed that when I am running any one of my engines slowly, the engine will make a humming/buzzing sound. As I run the engine faster, the sound will cease. And if I use my other transformer, a USA Trains Power 10, I do not get this sound. Does anyone have any idea as to why my MRC Power G is doing this?


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## rntfrmme (May 23, 2013)

Maybe because it doesn't know the words........I'm sorry I couldn't resist. I'm no electronics guy so no help from me....:-(


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## Totalwrecker (Feb 26, 2009)

Give 'em a call ...(732) 225-6360


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## Dan Pierce (Jan 2, 2008)

I would suspect a pulsed power output is the culprit. Install a linear device on the output like they use on the revolution to make pulsed powewr look to be linear by soothing out the pulses with capacitors.
Decoders especially do not like pulsed power as they see a pulse but can not sync to it as it is not a dcc signal.
And then there is Marklin decoders which look for in this order.. Marklin digital, DCC, and lastly DC power. If you have a digital system, you can turn off marklin but it will still look for DCC before it goes to DC.


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## choochoowilly (Oct 31, 2016)

I know that most MRC transformers are not pure Dc and have a pulse in them


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## Mark_s (Jun 24, 2013)

Actually the Power G is not pulsed, but it is not filtered very well, so it has a lot of 60Hz in the output.
I looked at an MRC power G, with the output set to 12V and a moderate load (1A) - the output varied by 6.8V peak to peak. By comparison, a Bridgewerks 5A supply (Magnum 5 SR) at 12 V and 1A out has less than 0.1V of variation.


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## Dan Pierce (Jan 2, 2008)

6.8 volts of peak to peak sounds like a pulse to me and would cause a motor to hum.


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## Zigeuner (Mar 9, 2013)

I'm a couple of months late here, but: The thing to do with your MRC power device would be to check the output with an oscilloscope. If there are pulses, they will show up on the screen. I don't know much about the MRC. If you had a schematic, you could determine whether there was enough filter capacitance to get to the level of pure DC. 


Several years ago, I built a dual (A and B Cab) power supply for my model railroad which has about 165 feet of track around the second floor wall of my barn-workshop. I used my oscilloscope to examine the output of the units and found that I did not have enough capacitance to fully clean the output. After some trial and error, I settled on a compact capacitor of 6,800 micro farads on each side and now the outputs are very nice and clean.


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