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Fixed volt PS vs. Variable volt PS

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  • Fixed volt PS vs. Variable volt PS

    Hello there -- my friend recently started a slot car club with Carrera Digital track. My friend is new to slots, and I'm returning after a 40 year hiatus. It's never too late to have a happy childhood, IMHO. Our current layout is about 140 feet. He made a large purchase of track sections, and the vendor threw-in an inexpensive, Chinese-labeled 20v 10a variable power supply.

    Today, after turning it on, the cars were slow and stuttering, and shortly, the track control unit started blinking and squawking. I noticed that the variable PS wasn't reading the correct voltage, so I turned it up to read 16v with 14.2 at the track. The CU liked that better, but the cars still weren't behaving right.

    Shortly thereafter, I noticed that the control unit wasn't reading the voltage I'd *just* set, and adjusted it again. Now, no dice. With the voltage knob all the way up, it wouldn't produce more than 12v, and pretty shortly thereafter, quit producing voltage at all.

    I'm no electronics tech, but I popped the cover and looked for obvious problems or fuses on the board, but found none. I assume the PS has failed, and that we're in the market for a new PS.

    Here's the question:

    A quick search on Amazon shows an 18vdc 10a power supply with fixed volts & amps. And it's cheap - $23.

    Is there any reason the PS *has* to be variable, or is it OK to run the fixed volt PS?

    I've already installed a fuse holder in the Carrera PS cord along with banana plugs for the PS.

    Thanks, I look forward to the sage advice.


  • #2
    No, you can use a fixed 18v. That's what D124 PSUs provide. It's nice to be able to adjust the voltage, but if you're on a budget and that fixed voltage one is the only option, go for it. If you can swing the extra cash for a half-decent variable voltage one, do it. You will absolutely not regret it in the long run, even if you end up using it for something else in the future. ;-)


    • #3
      OK, great. As I suspected. Thanks for the confirmation.


      • #4
        You have to be careful when you replace the power supply for a digital track. For a start you might risk damaging the control unit and if the voltage is set too low the lane changers might not work. The stock power supply should be adequate for the cars that come with the track, you might need a bigger power supply if you run cars with more powerful motors, but the control unit may not be able to handle more current.
        It would be best to post your question in the digital or Carrera forum.


        • #5
          Thanks for the warning, Rich. I did do a search and found that most folks were discussing variable PS solutions, but I didn't see the logic. Carrera supplies the track with a fixed voltage system, and in my limited understanding of electrical stuff, the Control Unit is good up to 24v (for 124 scale) and I'm only powering it with 18v (for 132).

          Anyway, long story short, it was easy to install (the PS has screw terminals) and everything worked great: no more CU beeping, no more stuttering cars, and in fact, one of the lane changers we had written off as deceased started working again.

          Also, I discovered that the unit *is* adjustable, 10% +/-, so I can achieve between 16v and 18v at the track rails.

          Overall, I'm pretty darned pleased.

          Here's a pic of the unit:

          You do not have permission to view this gallery.
          This gallery has 1 photos.


          • #6
            i've used similar and found them very reliable, especially for the price! they do put out some EMI interference, which is likely not an issue here.
            one does have to be careful with separating and insulating the terminal block wiring though, as the AC line in is right next to the DC out. i used shoe goo on one and heavy electrical tape on another to make sure that i didn't get my fingers (or tools) in an inappropriate place.


            • #7
              Solid advice on insulating the AC input. This particular unit has a flimsy plastic cover, but I don't imagine it lasting too long.

              I think the next upgrade will be a plastic home wiring switch box with a light switch in the middle of the cord. The PS doesn't have a power switch!


              • #8
                Do you ever plan on running analog? If so, I'd highly recommend a variable PS. If not, a fixed unit is fine.


                • #9
                  Unlikely that we'd ever run analog.

                  Am I correct in assuming the variable PS in analog would perform the same function as programming the cars to run slower?


                  • #10
                    Originally posted by Roadracer_Al View Post
                    Unlikely that we'd ever run analog.

                    Am I correct in assuming the variable PS in analog would perform the same function as programming the cars to run slower?
                    Yes you are. At 12v the cars would be normal quick, then some might be super fast cars (like NSR if you have any). At 10v the super fast cars would be much more manageable to drive. If you have a SCP controller you'd be able to adjust the voltage right from the controller once it's put into Kid Mode.


                    • #11
                      Apparently, the only certain thing is uncertainty. My friend who owns the track just liquidated a hobby shop slot car inventory, and now we have over 300 analog cars!

                      He purchased an aftermarket control unit that intervenes between the Carrera control unit, and allows running analog cars, and binding digital controllers to the analog track.

                      Never say never, I guess.

                      He's got a lot of the cars on eBay right now. Mostly Fly, including a bunch of "presentation box" special models. I'm pretty excited about the Slot-It cars - I got an Audi LMP car which I've chipped for digital already, and might buy another. There's even a small number of Monogram cars -- I snatched up a Greenwood "Spirit of 76" Corvette! There are a bunch racing semi-tractor trucks, which just seems odd to me that companies committed effort to that *very* tiny niche interest. It seems that he got mostly stock that didn't sell -- some of this stuff is quite old.

                      So, yeah. Looks like we'll be racing some analog.