What information would I need in order to reser a decoder to its factory settings? I use an MRC Prodigy Advance 2 and the decoder is an older decoder in an Atlas loco.
You need to know what decoder it is. Different brands use different reset options, but the most common are CV8=8 or CV30=2. Both are read only CVs but will make the reset happen - if you read them back they will still show the previous value, CV8 being the manufacturer ID assigned by the NMRA.
Older decoders usually did not have a single CV reset option.
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
You should also read back and write down (I use a spreadsheet) any CVs you commonly change, such as locomotive address and momentum values. Otherwise you'll have to experiment with some of them all over again, because a factory reset will put them back to the way they came out of the box.
It takes an iron man to play with a toy iron horse.
Model Railroader magazine