Plenty of motor-only decoders fit just fine without removing the factory board. It's when you need to find space for the speaker, too, that you could use extra room (or use a ridiculously tiny speaker and end up with a quiet loco). First ones I did, I dropped a TCS T1 behin the cab and ran the wires back along the top channel and connected them tot he wires from the trucks, motor, and lights by just disconnecting them from the factrory board and attaching tot he decoder wires. That way I could just reconnect everything to the factory board if I wanted to switch it back, yet did not have to deal with the circuitry on the factory board. These didn;t have Mars lights, so I just swapped the headlight for an LED.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I have installed sound in several Proto E6 and E7s. DCC ready is a cruel joke. I have had to remove every factory light board and hard wire the decoder in, for the shell to fit back on right. There is plenty of room at the rear of the loco. You just need to remove the factory light board!
What I would do is strip out the factory board, and carve out some space for the decoder in the middle of the frame. In the rather huge space in the back where the factory board was, you can put a fairly large speaker and enclosure. Maybe even a second smaller speaker up behind the cab.
I have a Proto E6. It is DCC ready and has the NMRA 8pin plug. I have tried installing the Soundtraxx TSU-1000 decoder, but then, I can not get the shell to fit back on the frame. I can't find any other way to mount the decoder except at the rear of the loco with the speaker just behind the cab. I need suggestions.