I’m hoping this is just some simple thing I’m missing.
I have a 7’x15’ shelf HO layout that is DC, running a Railpower Tech 2 1400 power pack. It seemed to run mediocre at first because I only had one terminal connection, with trains slowing down at the far end of the run. So I got this great idea to add a main distribution board and run feeder wires to it every 3’-5’ of track using solid #20 thermostat wire (which made for LONG feeders with no main buss wires). The trains no longer slowed down at the far end, but they seemed to need much more throttle to run. Maybe too many and too long feeders? So I decided to go to #12 solid copper wires for a buss and do away with the main distribution board idea. Now, even with the throttle almost wide open, a loco hardly moves at all, and the overload light comes on for the power pack. Even if I take the other end of the #12 wires and touch them securely to the track, a loco hardly moves. What am I doing wrong? What do I not understand?
How did you attach the wires to each other? How are the feeders attached to the track? You problems got worse as you added more connections. This says to me that you have high resistance in your wiring connections.
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you might also want to grab a multivolt meter and check to see if you have somehow shorted the rails together with your additional track feeders. Some turnouts will cause this if the frog is all metal, the work around (for DC) is to gap the frog on the diverging route, so that the + and - don’t touch.
Without knowing how You wired all Your feeders to the one power pack, (which is not a very powerful pack, probably less than a amp & 1/2) start by disconnecting all Your feeders from power supply and start with Your closest connection to power supply and test with engine, if it works, go to next feeder connection and connect that to the one that works, in a daisy chain fashion, not directly to supply, testing each one after connecting, keeping Your plus+ negative- connections constant, hopefully You are using a color code, like Red, Black etc. If You run into a problem, like short or breaker tripping, that area with the feeder has a problem, turnout, whatever.
Get 20 feet of “lamp cord” wire (usually #14), rip it in half, and make yourself a buss wire to run the length of the layout. Attach your #20 feeders to the buss, keeping the feeders less than 2 feet in length.
Also, make sure you have feeders hitting every stub siding and every 4 feet or so of track.
This will clean up the underside of the layout and significantly reduce “drag”.
Don’t rip it all out. The #12 bus is fine. What you’ve probably done is get a couple of the feeders hooked up the wrong way. Hopefully you used 2 colors for the feeders. If you trace around the layout with a finger on say the outside rail, without lifting it, the feeder connected to that rrails hould always be the same color, and connected to the same bus wire, If your finger ends up on the inside rail without lifting it, you have a reverse loop which will require different handling. But make sure all the feeders are hooked up correctly. One or two backwards will give a strange result like you are seeing and not necessarily an instant short.
You should use this opportunity to make electrical control blocks for your layout. Doing this allows you to turn off certain sections of track while others are turned on. This allows you to park a train on a siding while another train passes, etc.
Each block will be a much smaller amount of track than the whole layout (or they can all be on at once.) It will make it easier to trouble shoot problems. My policy is every time the mainline comes to a turnout each fork is a new block.
You didn’t mention how many locos your are running at a time. Did something change on one of them? Just another possible thing to check while trouble shooting.