Buzzing GP7 DCC

[El Loco]

Last week I purchased a DCC on board GP7.  The engine lights up and runs but buzzes loudly, especially at low speed and won't hold steady speed.  I am powering my layout with a Digitrax zypher extra.  Also, I have to turn my throttle up to 1.5 before it even moves.  I this how these engines run?  Is there something I can do to get it run better?  I took it apart and didn't find anything major wrong with it.   

[Jim Banner]

Getting your locomotive to start at about .5 on your Zephyr throttle is easy - just increase the start voltage setting in the decoder by increasing the value in CV2.

A really loud buzz and uneven speed are a bit more troubling.  Bachmann locomotives tend to produce some decoder noise because the decoders are not designed for silent running.  But most would not consider it loud.  Do you have another Bachmann diesel to compare it to?  Uneven speed is often associated with dirty track, dirty wheels, or dirty pickups where the power is picked off the wheels.  With this type of problem, you will often see the headlight flickering as well.  But if the buzz is loud and the headlight does not flicker when the speed is erratic, there are a number of other problems that could be happening.  You mention that you did not find anything major wrong with the locomotive.  But maybe there is something minor wrong with it.  A wire rubbing against a drive shaft or flywheel can make a lot of noise and affect locomotive speed, especially starting speed.  A wire jammed between the locomotive frame and the shell can amplify any small noise that is present.  A bad decoder can cause any or all of the effects you mention.  If the locomotive was bought used, the decoder might be a non-Bachmann one that was not properly installed.  A bad motor, particularly one with some foreign material inside it, can also cause  noise, speed variations and higher than normal starting speeds.  A binding gear or one with a bit of moulding flash on it could cause your problems as could a drive shaft that is installed too tightly i.e. one of the universals not pressed all the way onto its shaft.  Having inspected you locomotive for major problems, you next step might be to inspect it for these minor problems and any additional problems others may add to the list.

If all else fails and you bought the locomotive new from a Bachmann dealer, you also have the option of sending your locomotive back to Bachmann for warranty service.

Jim