I have a relatively large layout powered by a Digitrax DCS240. In one section of the layout, every one of my locos operates in fits and starts, surging ahead an inch at a time. The layout section is electrically far away from the DCS240 (but other, working, sections are further) but near to a power tap off the bus. I've done many things to address the problem:
1. The green light on the DCS240 is flashing every few seconds. According to the manual, this means it's operating in "safe operation mode," wherein it supplies less than 8A in order to protect itself. Supply voltage is 18v, which is within the suggested 3v of track power. So the unit should not be in safe mode. I don't know how to further diagnose the issue, and I don't even know if this is the cause of the surges.
2. I've cleaned the track vigorously. Ditto the pickup wheels on the locos.
3. There are nearby power taps off a track power bus. Regardless, the problem occurs even when I jumper the rails to adjacent sections that don't exhibit the surge problem. This rules out loose rail connectors as the source of the problem.
4. The problem does not seem to correlate with how many other locos are running on the layout.
5. The rails are definitely not shorted, as verified by an ohm meter.
6. I have an RRAmpMeter on order.
It is only partially the locomotive, and apparently not the tracks or their power supply. Gear slop throughout and other looser tolerances that add themselves to the frictions in the various trucks with rotating axles and also coupler slack. It's annoying, but....whaddayagonna do?
It occurs to me that the slope or combination of slopes in succession makes the entire train behave like a caterpillar in this unique area. You say it doesn't happen elsewhere, so it's not electrical in view of all you have done to ensure good electrical service. It must be mechanical.
It's very likely mechanical, but starts and stops can also be due to poor signal. Make sure the quarter test passes in the problem area, if the system does not shut down, add more feeders.
The "safe mode" indication has nothign to do with this - but if your power suppyl is 16V, unless it is well regulated, under light load I'll bet it measures more than 18V. Standard track voltage int he HO setting is 14.5 volts, so even 18.00 volts is more than 3V over the output voltage, which is the threshold for "safe operation mode". A typical laptop power supply at 15V DC is actually plenty to get a 14.5V track voltage. But all it means when in safe operation mode is that the current output is reduced - not to some miniscule level liek 1 amp or less, but you won;t get the full 5 amps out of it (or 8 amps if you are using an 8 amp power supply).
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Quote.
"every one of my locos operates in fits and starts". How many and what type of locos, decoders?
Only in a section would tell me electrical in that area, not mechanical right now. Really a strange one.
Not familiar with the DCC system. No idea what else is drawing DCC power if anything.
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.
waltoney3. There are nearby power taps off a track power bus. Regardless, the problem occurs even when I jumper the rails to adjacent sections that don't exhibit the surge problem. This rules out loose rail connectors as the source of the problem.
so a loco runs OK on a nearby track, but not on a problem track jumpered to the nearby track, at the same time? (locos only, not pulling any cars)
have you measured the voltage on these rails, compared it to other OK sections, with locos having problems?
(i had a problem where the weight of the loco flexed the track causing a problem. focus on trying to isolate the problem).
greg - Philadelphia & Reading / Reading
richg1998 Quote. "every one of my locos operates in fits and starts". How many and what type of locos, decoders? Only in a section would tell me electrical in that area, not mechanical right now. Really a strange one. Not familiar with the DCC system. No idea what else is drawing DCC power if anything. Rich
Let me ask you this. What is that one "section"? Is it a separate power district, a reversing section, an occupancy detected section? Is it electrically isolated from the rest of the layout, and how is it isolated?
Alton Junction
From: Electronics and DCC - Automated Email <noreply@trains.com>
> Let me ask you this. What is that one "section"? Is it a separate power district, a reversing section, an occupancy detected section? Is it electrically isolated from the rest of the layout, and how is it isolated?
No to all of these questions -- it's a section, about 30 feet long, in the middle of a long stretch of level track that's all connected together via a power bus under the table and with tight rail connectors. The fact that the surges still happen even when I jumper the rails to an adjacent section of track rules out nearly all of the electrical issues I can think of.
Part of the section is overballasted and was once exposed to spray adhesives, but about half isn't. I've been over the whole section both with toluene and with an abrasive track cleaner many times.
I'll try some more experiments based on the advice you all have given me. And maybe the meter I'm waiting for will shed some light on it.
If it's overballasted - is there ballast in the flangeways that is literally lifting the wheels of the loco slightly, causing loss of contact with the rail?
If you've got a solid bus and feeder system, then the power's getting to the track just fine. The key to it being a signal vs actual power - when the locos act liek this, do the headlights also flicker, or stay solid? If the headlights alsoo flicker, you simply aren;t getting power fromt he rails to the decoder.
Ballast lifting the wheels slightly may have been part of the problem, as was the sheer mechanical difficultly of pulling 9 Superliner cars plus a baggage car through trackwork that was ever-so-slightly narrowed by crud. In any case, I replaced the overballasted track and added a power tap. Trains run fine through this section now.
Thanks, all. I think we can consider this problem resolved.
Well that is one for the books. I never thought of track work but was out of touch.
Nice that you came back with results. Great trouble shooting.