I just switched over to DCC. I have a MRC Podigy system and am using MRC decoders. My Athearn locos are now making a loud electric buzzing sound when they are starting up. They never did this, and still dont, under DC power. My other locos, Walthers and Proto's are as quite as ever. Is this normal? Is there any way to fix this? HELP!!!
You have installed decoders in the athearns? (DC locomotives that are stationary on a DCC layout tend to buzz) I can think of two reasons for a DCC-equipped loco to buzz: during disassembly, something asymmetrical in the gear-train (little square bearings are my favourite) was installed backwards, so now it rattles / causes a spinning bit to be mis-aligned and thus be noisy. Noise tends to increase with engine speed so-called "low-frequency" decoder has the PWM frequency below 20kHz, thus audiable. Noise tends to decrease with speed All decoders work by pulsing full voltage to the motor to make it spin. Short pulses far apart at low speeds, and almost continuous pulses at high speeds. But this causes the motor to growl a little. Some brands of decoders make the pulse frequency too high for humans to hear, thus they buzz less (and annoy the neighbourhood dogs ) I've never met MRC decoders, so I don't know what frequency they run at. Found a website that covers it in a bit more detail: http://www.dccwiki.com/High-Frequency_Decoders Alternatively, if the buzzing gets louder as you wind the throttle out; especially if this was a hard-wired install, it's possible you accidentally rotated one of the little bearings (they're not square, trust me!), and now that drive shaft is slightly askew, meaning noisy. In this case, it will still be noisy without a decoder fitted. If you didn't disassemble the gear-train at all: a nice plug and play install, then this is unlikely. Only solution here is to pull it all to bits, and try to work out which bit needs to be rotated to quiet down. Listening carefully with the shell off might help here. The bearings I mean are the little black bits around the worm gears in this photo: With the shell off, if it definately sounds like the motor itself growling, you're back to cause A: decoder. Anyway, that's all I can think of. I'm sure others will have more suggestions.
Thanks for the info. I checked everything and it appears to be from the frequency of the decoder. I'll keep working on it.
I would like to hear how this was solved whenever you finish the project. Good info on the drive train; it is subtle. Thanks.
It's only subtle until you put the shell on, that seems to amplify the noise. Can make tracking down which one was 'it' a little bit harder. 4 bearings, 2 valid rotations each... 16 combinations? And if it's a hardwire, each disassembly to check is a chance to pinch a wire and start a fire I now pay attention to which way they were when I dismantle an engine!
