Disappointed with motor hum


B

bgm1961

New Member
Hello all,

I’ve found a couple other threads in this and other forums that “dabble around” my question but none that hit the mark, so… I'm back into N-Scale after 20 years. I recently pulled out my old MRC Tech II DC power pack to run several Atlas and Kato locos, all manufactured in the past five years. Each loco produces an annoying motor hum, no matter the speed. As soon as the loco receives power, even when not moving, the motor hums (loudly). Six locos all sound the same. I don't remember this as a characteristic when I was in the hobby 20 yrs ago (but I don't remember my anniversary either, so maybe not relevant)!

Is this normal for N-scale and DC power packs? Or is it more of an issue with the power pack itself? As mentioned, I'm using a MRC Tech II pack and guess its close to 20 yrs old, if not older. I bought it back in the day because for home layouts, it was apparently at the height of technology... the box boasts "Proportional Tracking Control" and "Automatic Pulse Injection"... both which are terms that tells me my 20 yr old pack is probably screwing with today's modern motors.

Thoughts? Would the hum go away with one of today's DC power packs?

And yes, I WILL BE going to DCC in the near future, making this a moot conversation. But not for another year. In the meantime, I'd like to run a few trains without that annoying hum.

Thanks in advance for your thoughts,
bgm1961
 
Try putting the locomotive on a piece of track that is not part of your layout, and place a 9 volt battery on the rails, touching each terminal to a rail. That's pure DC and you'll be able to see if there's a difference in sound.

timothy dineen
 
Is your Tech II a 1400 or 2400? If it's a 2400. turn the pulse to "off" and try that. Mine all used to hum when pulse power was used.
 
Thanks to both of you for your replies. My MRC is a Tech II 2500. Based on your input, Timothy, I did the 9v battery test and my locos are dead quiet. However as soon as I hook the MRC Tech II 2500 power back to them, they hum/buzz. Looks like I'm buying a new pack!

Thanks again,
bgm1961
 
I have the MRC Tech II, all my engines hum at start up, more like a growl, typically disappears as engine speed increases.
 
Sounds like feedback of some sort which is usually indicative of a short or too much load on the power supply.. I'm not familiar with the particular power supply/controller you have but have you tried running a single loco on it's own with no other stock on the rails??


Have you also tried running the loco on a separate piece of track as you did with the 9v battery??
 
The deal with the pulse power is that it's sending pulses of power to the motor. Those pulses make the motor armature vibrate, which creates the hum.

A loud hum from the power pack would indicate a problem. A humming motor is pretty normal with a PWM (pulse width modulated) speed control. (The one loco I've converted to DCC hums too if I turn on the momentum effects.)
 
bgm1961 said:
Thanks to both of you for your replies. My MRC is a Tech II 2500. Based on your input, Timothy, I did the 9v battery test and my locos are dead quiet. However as soon as I hook the MRC Tech II 2500 power back to them, they hum/buzz. Looks like I'm buying a new pack!

Thanks again,
bgm1961
Click to expand...

Why not just put a filter cap across the output of the power pack if you are using DC and not DCC???? A filter cap will smooth it out and stop the hum.

I would not think a GOOD pulse unit would hum. It should whine faintly at high pitch but never buzz. If it buzzes at all, it means 120 Hz ripple from unfiltered DC. That isn't exactly a pulsed system that keeps torque high.

Take a variable speed battery drill and start it slowly, and listen to the whine. That is the type of noise, or even higher pitch, any true pulsed supply that keeps torque up and speed down should make.


Tom
 
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