I bought a couple of 2-6-6-2 Mallets a couple of weeks back as the main retailer had very few left in stock, one is a sound one the other a 'silent' one ( in fact the sound one was the last one in stock)
The sound one ran perfectly on initial testing but the 'silent' one was not up to expectations certainly not as good as our other mallets, I did the usual tweeks with the decoder altering CVs etc and whilst this improved perfomance quite a lot It still wasn't as good as it should have been.
This afternoon I was removing some decoders from a couple of UK locos I had sold. So I had some decoders going spare!
I had noted that the 2-6-6-2 I was concerned about had a 21 pin socket but was fitted with an 8 pin decoder via a 8 to 21 pin adaptor cable.
So I removed the 8pin decoder and cable and fitted one of my spare 21 pin decoders ( this is a Bachmann 4 function one) I tested the loco with the relacement decoder and the running qualities were perfect!
I have no idea why this should be but I am quite happy with the situation, some of our earlier 2-6-6-2s have 8 pin sockets and 8 pin decoders they run fine!!
I have been using digital for many years, ( since '98) and I have become very aware that strange things can occur sometimes, which are not always easily explained
I had this issue with the 2-8-0 as well. The stock decoder was not happy at all, so I replaced it and the engine ran just fine.
Strangely, I put the "bad" decoder in my shay where is works just fine to this day.
Makes no sense, but whatever works...
Scott