Thank you for your reply. Come to think of it, Kelly (of QSI) mentioned the motor output runs through an H bridge chip. I don't know about availability. Have you tried directly contacting Kelly?
If you have a replacement Titan I would use it. There are so many feature upgrades in the vastly superior Titan. Gone is the crappy prime mover (UFO whir) sound.
The Q1 decoder can be repurposed into something else. e.g. a commuter cab car with horn, bell and lights. I did a couple of commuter cab cars with repurposed Revolution decoders (great horns and lights, but lousy prime movers) turned down all motor and prime mover functions and it works beautifully. Alternately, the Q1 would probably make a decent caboose decoder.