Bachmann DCC - Jerky start

[hjmurray]

I have just installed a Bachmann decoder in an Athearn GP9 chassis. The motor is all nicely insulated from the chassis, the correct wires are connected to the decoder and the black wire is tightly grounded to the chassis. However when I run it the engine is jerky at start up or does not start at all unless I give it a little push. When it get rolling it runs very smooth. I ran the motor in DCC mode before I pushed it back into the chassis and it worked fine. It also runs OK when I put it on a DC track and starts up very nice.

Any suggestions?

Thanks

[Andy Fekete]

i have the same problem with my spectrum 2-10-2 the loco wont start until i crank the trottle up to 1/2 speed the answer is the deacoder does not have a feature (somebody told me on the forum a while back but i forgot the name) it means you have to give it more juice to make it start than a normal loco with time and running this effect will go away.

[Jim Banner]

How did these locomotives run on dc?  If they had higher than normal starting voltages and liked to jump start on dc, they will do the same with normal DCC decoders.  Back emf control often helps but requires a decoder with BEMF built in.

[hjmurray]

Hi Jim

It works very smooth in DC. At first I thought it might be poor electrical pickup in the trucks but DC mode works OK.

[Jake]

Try checking your starting voltage. (assuming you are not using E-Z Command)

[hjmurray]

I am using EZ Command. However it seems to be the electrical pick up from the tracks. I used jumper wires to connect the track directly to the orange and gray wires on the decoder and motor runs as it should.

The electrical pick seems OK when I run it in DC but not adequate in DCC.

Any suggestion on improving the pick up on the Athearn trucks?

[Hunt]

Double check your wiring for good connections.

Clean the wheels and place a very small amount of conductive contact lube on the wheel tread and electrical pick-up rub points.

[hjmurray]

Thanks for the suggestion. What is the conductive contact lube called?

Sorry I may have mislead you folks on my previous message. I connected the jumper wires from the track to the black chassis wire and my red wire to the truck connections. (Not the orange and gray.) I have run a wire to both front and back truck connections and soldered the red lead from the decoder to that.

[Hunt]

What is the conductive contact lube called?

Bachmann labels theirs Conductive Contact Lube.
Atlas labels it Conducta Lube-Cleaner

[hjmurray]

Thanks for the names of the conducting lubricant.

I am using a Bachmann decoder in an older Athearn GP9 that has the white plastic base under the motor. I pulled the motor cut off the 'wings' on the copper clip that holds the brush spring in place and soldered on the gray decoder wire. Then did the same to the copper clip on the top of the motor and soldered the orange wire. According to the spec sheet with the decoder these are the electrical leads to the motor, after you have isolate the motor from the chassis. And according to the spec sheet it is the black and red leads that are connected to the right side and left side of the pick-ups from the track. When I run jumper wires with alligator clips for the rails directly to where I connected the red and black leads the motor runs perfectly. It is jerky at start up when I am drawing the current through the wheels. That leads me to conclude the problem is with the pick-up brushes on the wheels.

[Hunt]

Pick-up and some other part of the drive train may be the source. If pick-up source, the conductive lube may help.

Also visit a model train store, club or a friend with a DCC unit capable of programming and experiment with different values in CV 2, Starting Voltage, (Range 0 â€" 31). The value you leave in CV 2 will be what the decoder uses when you control the locomotive with the Bachmann Command Control Center unit. 

[Virginian]

If it does not do it on DC, and does do it on DCC, why in the world do you think it's the trucks pick ups?  AC (okay, not classical AC sine wave but close enough) flows exactly the same way as DC, and it has more EMF to push it in this case as well.

[hjmurray]

Good point.

So what is the problem? It works OK when powered DC. It works OK when I clip jumper wires from the rails to the points on the loco where I connected the leads of the decoder. It seems to me that narrows it to a problem between the connection point and the wheels to the track.

In some of the reading about DCC I have been led to understand the conductivity of electricity is more critical under DCC that DC. Such as making sure all rail joiners are soldered. Using a larger gauge buss wire than used for DC and also using more 'drop' wires from the track to the buss wire.

[Virginian]

Ever think it might be the decoder? 

[hjmurray]

Perhaps. That was my first thought until I connected wires from the track to the points where I attached the black and red decoder leads to the chassis. Red went to the metal 'tongues' on top of each truck and I grounded the black to the chassis. and the motor operates perfectly. It is just when I try to run it on the rails that it does not start without turning the flywheels a bit and have the speed knob up to the 2:00 position of my Bachmann DCC controller. I ran it for 15 to 20 minutes at a fast speed around a loop on my layout. there were a couple of points along the way where it slowed a bit then speeded up. That fit with my understanding, as mentioned in my previous post, that my electrical connection on the track are not sufficient for DCC. However that said I have a Bachmann F unit and a Bachmann GP35 both with factory install decoders working A-OK. I also installed a Bachmann decoder in a Bachman GP30 and that one runs OK.