I had the best decoder installed in our tiny club to install a decoder in this loco. When it was finished it was finished. The decoder works but there's some condition internally that requires you push down on the boiler to get it to run. Since the headlight is blown too it's hard to determine if the mechanism is binding or there is an open contact.
Help! Where do I start?
Stoker
Here are my thoughts on your problem.
First, the headlight might still be working, as it usually takes a function button to turn it on or off. Dependaing on the decoder it might be different, but mine works using function 10.
I have installed decoders in 2 of the spectrum 2-6-6-2 and my suggestion would be to double check the two screws where you had to undo two of the wires and attache them to the decoder. I would double check the insulation on the solder joints. also check to make sure the screws are tight. a loose screw may not be making proper contact to begin with, thats why you would have to "push down" on the boiler.
Just my thoughs and suggestion. Hope this helps
anoldrail