Possible problem with Power Cab

[Mike C]

  Early this year I tore down the old 4 x 8 HOn3 layout . I now have a layout around the walls of a 14 x 11 foot room . On the old layout I was running most locos at speed step 30 (of 128) the locos now need at least speed step 45 to run at the same speed they used to . Do i need an SB5 booster , or should I try using a larger feeder wire to the track ? The layout is wired with with 12 - 15 drops to the cab bus {18 gauge} .  Oh and the wires between the Power Cab and the buss is a pair of 22 gauge wires about a foot long .    Mike

[Scottl]

I don't think a booster is likely needed. If you were overloading it (you don't say how many locos/acessories you are using) it would shut down.

The main feeders of 22 ga seem light relative to 18 ga for the bus, but mind you, the wires from the Power Cab are a lot finer than 22 ga so I wonder if it is something else?   It might be the locomotives need to be tuned up or at least run enough to overcome any deposits or gunt that might have built up in storage.

[Mike C]

  Usually have 6 locos total , although only 1 at a time will run the rest are powered up . I had some of these running just 2 months ago before I moved . I just think that there is a voltage problem somewhere . I probably need to test the track voltage .

[Scottl]

Seems like a good plan.  With those loads, Power cab should be able to handle it.

[Maletrain]

A few of thoughts:

1. Is the comparison between the two layouts an apples-to-apples situation, with the same radius curves and grades involved?

2. When I run locos after they have been sitting for even a couple of days, they take about 15 minutes to stop slightly increasing speed for each lap.  They tend to run about 10% to even 15% faster after they "warm up".  So, if you are comparing cold speeds now to memories of faster speeds months ago, it might pay to do the warmups and see if the difference is still apparent.

3.  Wiring resistance is both wire size and connection integrity.  Loose connectors can be a voltage drop problem.  I agree that testing the voltage on the tracks is a good way to see if there is some problem with resistance.  Try to do that with a load that draws about as much current as one of your locos, or one of our consists if you use one.  I use automobile light bulbs.  The nice thing about the Power Cab is that it will display current going to the track.  So, run a loco and measure its current, then find a light bulb that draws roughly the same amount of current.  Then go around the layout and see what the voltage is near the light bulb when it is lighted by the track.  If it is low farther away from the Power Cab (as the wiring path goes) then you need to check connections and, if they are good, try bridging the distance from the Power Cab to the low voltage location with a length of 14 gauge wire, to see how much that improves the situation.

The information you get from those tests should tell you what you really need to do.

[peteski]

If you use the same number of locos and lit passenger cars (if you even use those), then the current consumption will be the same as on the old layout.  Power Cab can comfortably supply 1 amp of current.  As mentioned, Power Cab has a handy feature where it can display the current consumed at its DCC output. Edit the settings to show that current and see what it is.

The physical size of the layout (total length of track)  should not matter.  It is the electrical load generated by all the current consuming locos and rolling stock that matters.

But the longer the track and DCC bus is, the more resistance it will have, and more voltage will drop there before it gets to the decoder.  If the Power Cab DCC voltage is 13V and on the old layout the track and bus resistance only caused 1V drop, then the decoder "saw" 12V.  If on the new layout the track and bus cause drop of 3V, then the decoder only "sees" 10V, so the motor will run slower as the same speed step as before.

BTW, spelling if the word describing a group of electical conductors is "bus" (only one "s").

[Mike C]

  I have the AMP display enabled and running 1 Blackstone loco with 4 others ideling I get right around .35 amps . I have a Brass K-28 that I need to check next . Last time I ran it it went about 12 ft. and gradually slowed to a stop . Wouldn't restart it was pulling 12 cars but there are no real grades on the layout .

[peteski]

  I have the AMP display enabled and running 1 Blackstone loco with 4 others ideling I get right around .35 amps . I have a Brass K-28 that I need to check next . Last time I ran it it went about 12 ft. and gradually slowed to a stop . Wouldn't restart it was pulling 12 cars but there are no real grades on the layout .

0.35A is well within the capability of a Power Cab.  Your problem is elsewhere.  You description sounds more like a problem with the locomotive.  Even if there was a large voltage drop in the DCC bus and the rails, you should still be able to crank the throttle up and get the loco moving.  Or maybe you do have hige voltage drop.  Any way you can measure the DCC voltage on the track close to that loco while the loco is stalled?

[Mike C]

  I think I found the problem . The Brass K-28 was having some tracking problems , Front tender truck lifting up , and it was coming off the track in a couple places . The tender was easy , just a drawbar adjustment . The track however needed a couple small sections replaced . Still need to solder joints in a couple places . Curse of the Brass locos LOL.

[GGNInNScale]

Hi    Put a few trains on the rails in different places to create a load for the PowerCab.   Take a voltmeter around the track, set on 20VAC range.   You should read about 14VAC from the PowerCab give or take a bit at the closest point to the power feed from the PowerCab.  If you are seeing less than ~13VAC at the far end of your layout, then you need larger feeder(s). 

[peteski]

  I think I found the problem . The Brass K-28 was having some tracking problems , Front tender truck lifting up , and it was coming off the track in a couple places . The tender was easy , just a drawbar adjustment . The track however needed a couple small sections replaced . Still need to solder joints in a couple places . Curse of the Brass locos LOL.

Yes, that loco was a suspect, but as you mentioned, you might want to improve your electrical scheme of getting solid power to your now-longer track.

[Mike C]

 Believe me , I've got feeders everywhere , I did the quarter test around the layout and the breaker pooped right away so their good .  I don't have a volt meter just an Ohm meter probably need to get one though .     Mike

[peteski]

Believe me , I've got feeders everywhere , I did the quarter test around the layout and the breaker pooped right away so their good .  I don't have a volt meter just an Ohm meter probably need to get one though .     Mike

You have a dedicated ohmmeter?  Interesting. Those are much rarer that just standard multimeters.  But even standard multimeters will not give an accurate voltage reading of a DCC signal. But even if inaccurate, you can still use to to compare the voltages it sees at the Power Cab's output, and some far place on the layout with a loco running there.

As far as the quarter test goes, sure that is good, but it might not be good enough to indicate small voltage drops.  For example, if the booster (in the Power Cab) outputs a 12V DCC signal, but the DCC bus and the rails have enough resistance to drop 2V at the far end of the layout with the loco running there, that will slow the loco's motor down slightly (running at a constant speed step), but it will likely still allow enough current flow across the quarter to trip the breaker.
I'm not saying that's what is happening, but it is a possibility.

[Mike C]

  I worked some more this morning . Turns out that the last part of the mystery involved the pilot . I had a couple of vertical curves that caught the pilot on the K 28 . Didn't affect any other loco so I figure the pilot was a bit low . Shimmed the track and it's running almost perfect except 1 place the pilot wheels derail . I'll figure that out next . Thanks everyone for the helpful ideas !    Mike

[peteski]

I'm glad you found a solution (which just happened to be mechanical not electrical).