Hey all, Does anyone here know where the gray wire lead goes from the decoder?? I have an HOscale Athearn F7A unit and I had my first decoder professionally installed and am trying my own F7A unit. My Walthers GP9 was really easy but I can't figure out where this wire lead hooks up to because it is somewhere underneath the motor. Any ideas?? Thanx in adv Matt
Yes it is on the bottom of the motor. There is a contact that touches the frame of the locomotive. You need to remove the motor, remove the contact, isolate the motor from the frame and attach a wire to the brush. David
If the Athearn F units are the same as their SD and GP units, the motor isolation can be accomplished with a strip of electical tape between the bottom of the motor and the frame. I leave the clip on the bottom of the motor and solder the gray wire to the clip. Be sure to test that there is no electrical connection between the gray and black wires. This is very important.
How do I go about taking the motor out??? Thanks for your help so far and for any you will give me. Matt
It has been a while since I did one but as I recall you just have to pull up firmly on the motor. It is held in place by some rubbery plastic tabs. David
You do need to insulate the motor from the frame, use more than one strip of electrical tape, as the strip will cut through the tape. DH121s are not good decoders, I blew three in one unit, but I put in a DMD and it works fine. The newer units have the motor mounts glued, to remove the motor, you need to push a screw driver up under the frame to release the motor without removing the mounts and destroying them. An Athearn is not the first decoder I'd want to install.
I think that blown decoders are always caused by user error, so to judge a unit's quality on whether or not it blows up is bull. Human beings make mistakes. Some won't admit it. There's nothing wrong with the 121 series decoder. It's cheap, basic and gets the job done. Nothing wrong with putting decoders in an Athearn unit either. It takes some effort, but I have seem pictures/heard stories other makes/models that take a helluva lot more. In any case, after the first one, they all get easier. All it takes is patience and care and you'll do fine. My one suggestion is to nip any exposed wire ends off until you're ready to use them. Then just restrip them and go to work - no accidental shorts from ends touching and screwing up your day. I can't confirm the glue and we'll have to take David's word for it, but my motors were removed by wiggling them back and forth while gently pulling up. After a few moments I had them in my hand ready to receive the new wires and the e-tape for isolation. G'Day!
