The safest way is with a DPDT switch. Just one switch. One side connects to the DC power pack. The other side connects to the DCC system. The middle goes to the track. Throw the switch one way, you have a DC layout. Throw it the other way, DCC.
Just make sure all your decoders do “analog conversion” (I don’t think those MRC ones do), and you can run everything on DC, until you start adding sound. The current Soundtraxx sound decoders can NOT run on DC and will be damaged. Whenever they get around to the new Tsunamis - those will work on DC or DCC, like the QSI sound in Broadway, P2, and Atlas.
Randy, I thought you’d be in Baltimore at the show.
Are those MRC’s worth the bother? I have a lot of locos to convert and I thought I might throw them in the Camelbacks which I see as more or less dragging big trains up from the staging yard to the classification yard. One is much stronger than the other though, and I thought I might have to program them to the same pulling speed.
Na, for one we don’t go to the spring show, for another I have to go to a wedding today, so no train show for me.
Those MRC decoders are, to put it kindly, junk. If you want a low cost but good decoder, you can pick up TCS T1’or NCE DS13SR’s for $13-$14. The NCEs even have a 6-pack at a discount price over a single unit. Both have high frequency motor drives, which the MRC does not, they both do 4-digit addressing, and both support a full range of CV’s, not just the most basic ones. The MRC decoders are probably fine for the Command2000 system, or the original Prodigy, where you can’t program all CVs anyway. But I would not use them for any full-featured DCC system. Especially if, as you say, you will need to do some programming to tune the two locos to run together.
Be sure to test those MRC decoders before you put them into your locomotives – I had 4 out of 6 dead on arrival. I’ll never touch another MRC product except their old, reliable DC power packs. Their decoders are pure trash.
If you don’t have a decoder tester - just wire it up to spare motor and lights outside of a loco, and connect the red and black to the track with clip leads. Program track first, see if it works. If you don’t put a motor or suitable load on the orange and grey, you won’t be able to program it.
NCE’s tester is probably the best all-around value, the only other thing you really need with it is a set of clip leads with the small ends, you can get those at Radio Shack, to test wired decoders that don’t have any sort of plug. Otherwise the NCE tester comes with cables to test 8 pin decoders as well as the ones with the 9 pin connector.
If you are really crazy, you’ll build one like I did. I made mine overly fancy, with a switchable current limiting resistor on the input side, and a switchable output t connect either a load resistor or connect external terminals to a motor. In internal mode I have a pair of LEDs to indicate forward and reverse, plus LEDs for F0F and F0R and F1.