The AT decoder has one advantage

The AT decoder has one advantage, you do not have to cut the shrink wrap off the AT decoder.  

With track power connected to the red and black terminals use a volt meter with one lead on the V+ terminal and verify which side of the diode is negative.  The 4 diodes are near one of the V+ terminals and the inboard end of each diode is likely the negative one.  

Once you verify the correct side of the diode solder the KA-1 black/white wire.  Connect the KA-1 blue wire to the V+ terminal on the decoder. You are ready to go.

Just completed a similar installation on a Digitrax DH123.  The improved running was well worth the effort.

Regards,

Dave 

Here's a quick picture

Verify the negative terminal of the diodes with a meter.

Dave

Wow fantastic Dave. Thank

Wow fantastic Dave. Thank you. That is very clear. I have an Athearn engine that I cannot get to stop losing power. It is the lead engine and the Mars light goes out. I have changed the wheel sets to North West Shortline. It helped, but did not cure it. I hope this helps. I have been told that it will.again thank you Dave. Jim Lowery

You're Welcome

Jim,

Keep us posted on your progress and please share any actual photos.

Dave

Well Dave it is in. Seems

Well Dave it is in.

Seems to be working. I am going to run the train a little today after I run the track cleaning train. Thank you very much for the help.

By the way, what are we exactly hooking this up to. I see it is a power source for a light. Should it be hooked up  to the forward light instead? What is the other wire hooked up to. I know it seems to be a negative, but why that one?

Thanks again.

Happy Thanksgiving

Jim Lowery

Try my column . . .

AT Decoder Wiring

Jim,

The AT style decoder has track power pickup terminals and V+ positive terminals on both ends.  The white headlight terminal is on the forward end and the yellow reverse light terminal is on the rearward end.  The motor runs on DC (direct current) so the track power (alternating current) must be rectified before the motor can use it.  Hence the 4 diode bridge as shown in the 2nd drawing below.

Hope this helps explain what is happening.

Happy Thanksgiving Leftovers,

Dave

Thanks again for all of the

Thanks again for all of the help. I guess I have some studying to do. I have several different types of decoders. I have found information on many of them (except for my MRC sound decoder which have served me well despite many peoples protestations). I will read more, and if I have questions I will be back. Jim Lowery