Mogul Headlight Not Working

[RailMan63]

Hey everyone!
I bought a Bachmann D&RGW #138 Mogul brand new on Ebay a few months ago.
It is the newer model with DCC.
So, for $100.00, it was a great deal.
The DCC board is a 21 pin model made by Soundtraxx.
Decided to put a sound decoder in it using the factory board.
I bought, and installed, a TCS 1525 Steam 121, 21 pin decoder in the tender.
Just like the Bachmann sound module, it is basically drop in.
Except for one thing:
You will have to turn the factory board around in the tender due to limited space.
After that, you're good to go.
And ,for those who don't know, the TCS decoder is far superior to the Bachmann sound module as it has far sounds and features at a price that is generally lower than the sound module is(if you can find one other than on the Bachmann website).
It's pretty fantastic!
I don't know what I've done , because the headlight no longer comes on.
I'm not certain what might be going on as I've checked out the wires in the tender,and they all look good.
I installed a TCS sound decoder just like this one in my 2-6-6-2, and it works flawlessly.
I'm thinking that I might have loosened a wire somewhere,but I don't see anything.
Any ideas what might be different with this one?
Thanks!

[RailMan63]

Ok.
Took a break from running my new Big Hauler Version #7 4-6-0 with DCC and  Soundtraxx TSU-4400 sound.
So, I finally decided to take an in-depth look at the mogul to see if I could figure out its' headlight issue.
Disassembled the tender and checked for a loose/broken wire.
All good.
Pulled the TCS 1525 21 pin sound decoder board to check for a possibly bent pin on the motherboard.
No problems there.
Had noted before pulling it that the decoder was not completely set all the way down on the pins.
Made sure that it was properly aligned and set on the motherboard after reinstall.
Removed all 4 wheel sets,cleaned all 8 wheels and lubricated the axles.
Reassembled tender.
Connected to locomotive and placed on tracks for testing with NCE Powercab.
Worked flawlessly, thusly answering my own question.
Mike
Thanks!