UP6Z and DCS-100

in dcc the voltage goes back and forth it is normal for n scale to get 8-16 volts but to high for z z is 5-8volts marklin azl 6-10 mtl 6-9

Ah! I'm dealing with this right now, so this is a great question!

There are a lot of "ifs" "and" "buts" so FIRST lets give the simple answer, then we can proceed to the more complex

Simple answer:
If you are running AZL locomotives with drop in decoders (Digitrax DZ123Z0 or TCS AZL4) then set up your DCC system the same way you would for "N" scale.

Now the more complex stuff:

1) You cannot use a simple handheld multi meter to measure DCC voltage. You need either: a DCC meter (I use a RRampMeter from Tony's Train Xchange) *OR* anything with an oscilloscope. You need something that can see the irregular waveform AC power that is DCC. A handheld multi meter cannot do that (unless it is an advanced one with a graph / scope, and that's more of an oscilloscope than a multi-meter)

2) Our modern AZL locomotives are rated for 12 volts. We did make some units that had 8 volt faulhaber motors in them years ago, but the locomotives that accept a drop in decoder are all rated for 12 volts. Another way to confirm - any AZL locomotive part number that starts with a "6" and has 5 digits is 12 volts. (6xxxx) No voltage drop needed for these.

3) I run my Marklin locomotives at 12 volts DCC without problems. This is a change for me - I used to drop the voltage, but I quit after years of experience.

4) What I do HIGHLY recommend is an advanced short circuit protection circuit. I use DCC Specialties PSX units. Totally worth the money and have saved MANY locomotives. No need to change any of the factory settings on these, just plug them in and use them.


Hope that helps!

Best
-Rob(A)

You might want to check out the users' manual around page 37 for instructions on reducing the voltage output and how to measure it.

The problem with most short-circuit protection is that it protects the throttle but not the rolling stock. Consider that the throttle protection will cut in at about 5 amps. At 12V that's 60 watts (think about the heat in a light bulb). That can melt applied metal parts and do harm to a stalled locomotive. I'm not familiar with Rob's solution, but I just use a 1A fuse: it's more than enough for 5-20 locomotives.

The DCS100 (and most DC boosters) does have short circuit protection. But it is not the best. It works ok for HO. For Z scale you need something that works faster.

Mark is correct that your rolling stock can get fried in DCC too. Turnouts are the problem. When that boxcar jumps the points and create a short circuit, a normal DCC booster is going to run a full 5 amps of 12 volt power through that little z scale wheel set. I've seen them melt the wheels and the plastic in the turnout in less than 30 seconds. Your DCC booster is clicking away, and you are looking for the source of the short circuit. In the meantime, the DCC booster is constantly re-connecting power to the short, looking to see if the problem is resolved. Every time it re-connects, it sends full blast power back down the line.

Better short circuit protection devices, like the PSX, actually have a separate microprocessor that does smart analysis of the current load. They can sense a short circuit in milliseconds, and keep the power off until the fault is cleared. That's fast enough to save z scale motors and wheels.

Mark also mentioned that a simple fuse would do. This may be fine for a normal DC system, but DCC s a very different beast, since it has the capacity to deliver full voltage an amperage to the rails at a moments notice, and continue to deliver that power. Chances are very good that your locomotive will be the thing that pops long before the fuse does.

Besides, we're talking about $35 for a device that works in all scales, and is protecting locomotives worth many multiples of that.

I like the PSX, but there are others. Price is good - technology is great.

One jumper will set the trip current to 1.27 amps. Factory is set to 3.81 amps (but I'm running up to 20 locomotives here, so that why mine is set so high)

I suggest 1.27 amps considering our AZL locomotives pull about .25 amps each - that means your good for at least 5 locos running full speed at 1.27 amp.

tonystrains.com/product/dcc-specialties-psx1-circuit-breaker/

I usually don't endorse products too heavily, but I've had 3 cups of coffee, so this is what happens.