Hi all. I have a MRC prodigy and I am wondering if anything voltage wise would need to be changed or modified in any way to make it safe for Z scale? Or is it good to go right out of the box? I am new to Z scale DCC but I am pretty familiar with N scale DCC. I am only scared that I might fry my brand new F7A because I know Z scale is a much lower voltage than N scale! Thank you in advanced for any and all your help!
No not really. MRC believes in power for DCC and that is deadly for Z scale engines for those new to DCC and not technically savy about DCC. The problem is what happens when you get a short on the track caused by the metal wheels of your loco which derailed at a switch. At the short there is power , power is amps x volts equals watts of power, ever tried to unscrew a 75 lamp bulb which has been burning for awhile. Ye it isi hot and that is what happens to the wheelto the site of the short on DCC track and if it sits there long enough there will be enough heat generated to melt something or smoke something. Yes circuit breakers are fineand they work in most cases but not in al cases. I have seen in HO and N the side frames of a trucks melted down due to shortthe valve geaer melted off a steamer or he plastic wheel centre melted down on a steamer. When you program your decoder you need to program the max voltage going from the decoder to the engine motor to 8 to 10vdc.but this does not address the amperage running through your rails. On many systems there is an adjustment for a trip time constant for your circuit breaker which sets the sensitivity of the breaker. I prefer to use the diode circuit shown on Atlas DCC systems for reducing the track voltage from 1 to 15vac to around 10 to 12vac in each power district and to then put a brake light bulb in each power district so if the circuit breaker does not trip you can see the lamp light up and that limits the power at the short circuit site to that of the lamp and gives you time to rescue your engine. Be sure to put the lamp up where you can see it when operating not hidden below the table or bench work Even then if you are going it alone in Z scale there is still a strong chance you will zap a decoder or motor or engine in the early learning stages. Go to a show where the guys are running Z on DCC and learn from them. Otherwise I recommend the NCE Power Cab as a better starting point for beginners to DCC for Z scale. Power to track is limited to 1 amp and track voltage is 12vac. You can later upgrade to a full 3 to 5 amp system but by then I think many will find that being able to run 3 trains is about all you can handle at first and most of us do not have large layouts in Z. I operate an 8 by 14 foot Z scale double track main on my layout at home on this system. using one for each main. Most LHS sources are used to HO and maybe N but not to Z when it comes to DCC. They push the line as per what they have learned in their scale of choice and it is not all transferable to Z. When programming your decoders enable the auto detect for DC operation if you have DC trackage around. This does not mean you can run from DCC onto DC track but it does mean your decoder equipped engine will run on either type of system. regards Garth
Which MRC Prodigy do you have ? The basic Express or Advanced? Both use a 15-16 volt power supply with ~14.5Volts to the track. This is too high for Z and should be lowered. The Express version is a 1.6 Amp system, the Advance a 3.5 Amp system. NCE's Power Cab is 13.75 Volts (about 12.5 to the track) and 2 Amps (not a 1 Amp). We all run Power Cabs at this voltage without "too high a voltage" issue. NOTHING will explode or be damaged under proper running connditions (NO shorts or STALLED locos). The MRC however is pushing it in my opinion. BOTH systems can be modified to run at lower voltages. You can do this in 3 ways: 1) the MRC and NCE systems use a DC power supply, you can either replace it with a 12 Volt version or, 2) Lower the DC input by adding about 8 to 10 diodes (power type like MR751 or 1n5400 series) that can handle 3 Amp shorts. Each diode is about 0.6V drop so 10 would drop ~~6 V HOWEVER this depends on Current thru them. With no or low current, they will drop only a few tenths (e.g. 0.2V), not the nominal 0.6V at rated current or, 3) Lowering the DCC side with 'back-to-back' diodes (2 of the above strings, in parallel, one reversed in polarity). As for the current, the 1.6 or 2 Amps is liveable however a bit much to run .02 or .16 Amp locos and light bulbs. If a short occurs (almost always on a turnout), both systems will supply that full rated current for about 1/2 second, then shut down, reset about a 1/2 to 1 second later and supply that full rated current again, over and over. Garth, what's my DCC motto ???? ALWAYS WATCH YOUR TRAINS. Unfortunately, that full rated current can flash a wheel wiper in the truck as they are small sized and don't make sufficient contact to carry that current so no current limiting is going to help all situations. If it is is just a wheel short, then that rated current (about 25-30 watts for starter systems) will be 'pulsed' ever 1/2 to 1 second and can heat that wheel up in a few seconds, enough to bend an axle, melt or distort a side frame, etc. Electronic Circuit breakers don't go low enough for our Z scale currents (ideally about a 1/2 Amp and definitely <1). DCC Specialties PSX series can get close. The automotive breaklight bulb is rated at ~2A. With no or little current flow, it is almost like a regular wire. When full voltage is applied, it heats up, increasing its resistance. But it takes ~2 Amps to do this so that same current STILL flows thru the wheel or wheel wipers. At the point of instant contact, that same full system current flows ! ALWAYS WATCH YOUR TRAINS If you have an Express system, just get the voltage lower and be carefull, like us, when running DCC. If everything runs around, everything is good. It is only when there is a Stall or a Short that you need to think fast. .
Whether intended or not the brick (power supply) with my NCE power cab is actually marked as 120vac 60 hz at 0.48 amps. cheers Garth
I should also add that I dont have any turnouts on my layout so I shouldnt have problems with deralements. I truly only want DCC in my Z scale to prove to my friend, that does HO scale, that it is very possible to run DCC easily in Z scale ahaha
it is my opinion that the NCE Power Cab has fewer pitfalls or traps for the first time user of DCC in Z scale. It was my choice fore my first purchase in DCC even though I had used other systems at various shows in the past 6 years after using this system I for 3 months I liked it well enough that I purchsed a second one. I now have 10 engines with DCC decoders. Most are TCS but I have a few CTElecktronik from Europe as well. cheers Garth
I am making an assumption that you are referring to a Micro Trains Lines F7. I am sure you are aware that it is not DCC or even "DCC ready" but only DC as it comes from the factory. Converting an MTL F7 to DCC is not for the beginner in Z scale unless you have had experience in milling (filing?) chassis halves, disassembly of locomotives, hard wiring / soldering DCC decoders and reassembling tiny parts. Once again not difficult IF you have experience. If you want to show your friend how easy it is to run DCC in Z scale, I might suggest an MTL GP with a TCS "drop in" board. I have numerous MTL F7 with Digitrax DCC decoders and use the NCE Power Cab with great success but at home and at train shows with the ZoCal group of modular railroaders. My reason for this comment is your word "easily".
Lindley, I completely overlooked that "F7" part ! Surf, it is assumed you are also converting the DC loco to DCC by modifying , in the MTL F7 or Märklin F7 case. Out of the box, the NCE Power Cab will be safer. But again, both can be made very safe by simply replacing the power supply with a lower output voltage one. Garth, that "0.48 amps" is the AC total worst case power consumption. Lets assume you have a 12V DC output at 2A. That is 10x lower voltage (120V AC divided by the 12V DC). So, the 2 Amps would be o.2 Amps to the 120V AC side, + the ineffeciencies in converting to 12V DC. That power supply MUST state the output current too. Or it wont get all those little logos and names on it. .
I have a CNC machine shop i have already modified and installed the DCC chip.. i know how to hard wire from my N scale experience. Im just afraid to put it on the track and test it untill i find the best DCC system to run with z scale. And also yes it is the Micro trains F7A unit.
There is a good areticle in MR for October on page74 covering DCC short circuits and solutions for same. cheers Garth
Thank you all! I think from what ive read the NCE power cab is the best way to go so im going to pick one up ASAP!
Good stuff there Surf. You can buy Function only decoders, Accessory decoders (motors, on/off contacts) and even use O or G scale decoders to run motors. On those larger ones, using a low power Power Cab, you can research the components on those larger size decoders and cut the trace supplying the motor's H-bridge driver, then connect that to an external 12V or such, higher current supply ! Garth, just recevied that issue and glanced over. I saw the humungous lightbulb solution, still too high a current for Z. Use a smaller bulb (like the "side marker" and 'drive lights' on a car, the 0.5 or worse, 1A versions. .
