I have a 120' N scale layout with two power districts powered by a Digitrax DCS 100 and 150 booster. The track in the district powered by the DCS 100 is measuring at 13.5v while the track powered by the booster is only 10.5v. Each district is approximately the same number feet of track and with the same gauge wire. What might be causing the one district to be weaker?
Defective feeders or track joiners.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
First questions: Do you have bot units set to the same scale and what is the voltage output of the power supplies you are using?
It looks like the DCS 100 is putting out HO voltage which my N layout is being run on with the DB 150. My voltage usually varries from 13.5 to 14.6 volts. With my DB 150 set to the N voltage it varries from 10.5 to 12 volts. But I am only using one command station/booster. Do you have two power supplies? Check the input voltage. They could be different.
Jim
Thanks for the quick replies.
When, I took the measurements, I did so in various locations along the main line by different feeders and sections of track. All the measurements were consistent, so I don't think it's feeders and joiners.
I checked the toggle switches, and both are set for N Scale.Then, I checked the input and output voltage at the terminals on each power supply. The input was 16.7v on each. For output, the 100 is 13.5v and the 150 is 10.5v (same as measured on the rails). So, the DB150 is running weak and I need to adjust the pot, yes?
With the DB150 set to N Scale, I've tried adjusting the pot but it won't produce more than 11.8v of output. So, I've set the toggle switch to HO and adjusted the pot to 13.5v. That will be okay, right?
Only hiccup now, is that the output at the terminals on the power supply is 13.5v, but on the rail I'm measuring 14.2v. That doesn't even sound possible!
Have you tried checking the output voltages on your boosters with everything disconnected from the track outputs? That would be the next thing I would do (actually, I would have done that before making any adjustments) just to elimate any possiblity of a wiring problem causingn what you are seeing.
I did measure the output of the power supply without the track wired to it as i was adjusting the pot. That's when I measured 13.5v.
Then, I wired the track back up. Still measuring 13.5v of output at the power supply, but on the rails I am getting 14.2v.
If your power supply AC or DC? If it's AC, this is entirely plausible. The first thing inside the DB150 is a full wave rectifier and filter capacitor. The charge pumping action of a filter capacitor in a power supply like that results in an input voltage to the circuit well above the AC output of the transformer. A 12 V transformer, a full wave bridge rectifier, and filter capacitor results in about 15V DC unregulated.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
mudekk01 the output at the terminals on the power supply is 13.5v, but on the rail I'm measuring 14.2v. That doesn't even sound possible!
in order to make sense, start at the terminals on the power supply and just move one meter connection at a time.
With nothing in between except wire, you should measure the same voltage on the supply as you would if you had one meter connection on the supply and the other on the rail. you can then swap, have the meter connected on the other supply terminal and the other rail.
greg - Philadelphia & Reading / Reading
If it's really bad, this should show it. However, a poor connection may show no voltage drop under no load conditions. If you can pinpoint where the loco slows down on DC, and where it speeds back up again, the problem exists somewhere between those points. Either insufficient feeders, so it's relying on the rail joiners, or if there are feeders, there are some bad connections to the bus. It's also possible that just one set of feeders is hooked up backwards. Often this won't result in a dead short, but rather all sorts of wierd operation.
He can disconnect the pack, remove the locos and check for resistance at the 2 now disconnected wires. If a feeder is crossed, it will show up.
He also can jump the disconnected wires and begin checking the resistance at the rails. It should increase slightly as he gets further away from the pack but not by a lot.
But the best way to check for drops is if he has a DC pack to substitute. Voltage drop can then be checked, even with a cheap DMM. Load the rails with a test lamp, connect one lead to the pack terminal and using a long test lead, go around the layout checking the same side of the circuit. Repeat for the other side and any drops, even small ones will show up.
I have been following this thread with interest.
I have two NCE boosters that I use to power an HO scale layout that is divided into 7 power districts, 4 on one booster and 3 on the other. Using RRampMeters wired in-line to measure voltage and amps, I get continous readings of approximately 15.2 volts for one booster and 13.5 volts for the other.
This prompts two questions.
How important is it to balance the two boosters so that each provides the same voltage as the other?
What voltage is best for the OP's N scale layout? He indicates that his layout shows 13.5 volts and 10.5 volts. The 10.5 voltage output on that second booster seems awfully low.
Alton Junction
A nearly 2 volt difference should give you a noticeable lurch in a loco as it crosses from the section powered by one into the section powered by the second. A half volt difference or less should be unnoticeable and what you really should strive for. It's also important for there to be a common connection between the boosters, at least with Digitrax, since they generate a true bipolar output around a circuit common, some others just have the ground side of the power be the negative half of the DCC signal, a mid point being the 'common' and the peak voltage being the upper half of the DCC wave. What happens when you cross the gaps between two power districts is that voltage difference flows on that common connection between boosters. If you do not use the common pins to connect between boosters with Digitrax, that voltage (and current) is on the telephone wire that is the Loconet connection. Since NCE does not have a ground or common connection, they usually use the booster case, it mentions in the manuals about running a common between the cases of all boosters.
Since the DB150 has a potentiometer to fine tune the voltage, above and beyond the 3 position switch on the outside, it's possible it was just left at the minimum setting when built. A double check with Digitrax is to measure the voltage between Rail A and ground, and Rail B and ground. They should be the same, or VERY close. If not, there is probably a fault in the track drive circuitry and the booster should be sent in for repair. Do make sure Address 00 is set to speed 0 - don;t assume, select it on the throttle and turn it down to speed 0. This can also cause a low voltage reading. Address 00 is the first thing to check if there is a significant difference between the Rail A/Gnd and Rail B/Gnd readings.
Randy, thanks for that explanation.
I run my DCC layout with DCC boosters, and I run a wire connection between the two booster cases.
If you only have 120 feet of track why are you using two boosters when you can use one and use the PM42 quad power manager. Might be the solution to your power problems. Jim.
12 volts is maximum for the n scale setting. 15 volts is maximum for the HO setting. Manual Section 7.8 . Measure with the track wiring disconnected like has been suggested. You may have to much voltage not to little.
Lee