I know you've heard it before, but "this one is driving me crazy". I have several Bachmann Spectrum Dash 8's, a couple of the non-DCC ready version and 4 of the DCC ready model. They all checked out on DC when first purchased. I converted the non-DCC ready versions to DCC using DigiTrax DZ123 decoders and hard wiring them after removing the original light boards. They ran beautifully! Crawl speed was amazing - 1-3 mph. They are both Dash 8-40CW locomotives.
Of the four DCC ready Dash 8-40C's, I had converted one. I installed the same decoder as the CW's, but I used the original light board and soldered it using the connectors on the board. It also ran beautifully!
Then, a few months ago, I discovered sound! Well, you know what happened then. Yes, I am converting all my locos to sound.
I installed SoundTraxx Econami 882001 decoders in two of the 8-40C's (the converted one and a new purchase), hardwiring them because I removed the original light board to have room for speakers. I actually put two speakers in the first one I did, then decided that was overkill and installed just one speaker in the second - sound is still amazing, though!
As I said, they both ran great before sound - the first with the DZ123 and the second on regular DC before conversion. Now, however, I have a problem. Both of the locos stall intermittently at very low speeds - not always and not in the same location on the track. Sometimes it is a "pulsating" stall - run,stop, run, stop, etc. then it will stop altogether or continue normally until the next stall event (which may be a foot later or 10 feet later).
When there is a hard stall, there is a corresponding voltage drop. I measured this by carefully connecting a VOM to each side of the frame and monitoring the voltage as the locos ran. I assume there is a similar drop during the "pulsating" stall as sound quits momentarily and headlights go off, but I can't detect it with the VOM. If I lightly touch the top of a loco during a hard stall (and I do mean VERY lightly), it will start and run until the next event.
I have made sure track is clean where the locos run. I checked railjoiners, continuity and voltage - no problems in those areas. There are well-soldered feeder wires right in the middle of the track I am using to test. Voltage to the track registers a solid 16.5+.
Could there be intermittent binding in the gears or wheel sets at low speeds? Might the decoders not be delivering the necessary voltage at low speeds? CV 2 is set at 0 and the locos have no problem starting or running at speed step 1 of 128 when not stalling.
The stalling events also occur as described above when the converted locos are run on a section of DC test track.
There you have it. I now call on greater thinkers with more experience than I to cogitate, detect and suggest.
Sounds like the locos have been handled extensively. First thing I'd check is to make sure all the wheels are flat on the deck and confirm the trucks aren't twisted somehow. Get a piece of plate glass, set the loco on it, then try to nudge the edge of a sheet of paper under each wheel. The paper should show resistance, although you may be able to slide it underneath the wheel. You do not want any gap where the sheet slides right under, as that indicates a wheel that's riding high.
If everything checks out straight, flat, and in contact, then on to more diagnosis. If the truck did manage to get warped a little from handling, usually some gentle straightening will work, then test again to check for improvement.
Mike Lehman
Urbana, IL
Thank you for taking a break from "feasting" to reply to my post.
Ran the test on both locos. The worst offender failed miserably. Both sets of trucks have issues. Both the front and rear have a single wheel "off the ground" on one side and all three wheels "off the ground" on the opposite side. I'll look into repairs after turkey day.
The second (new as of last week) loco did not exhibit much in the way of gaps. I will check it more closely, however, after addressing the first one.
Thanks again and Happy Thanksgiving!
You don't mention in any of Your testing etc. and Mike appears to have not mentioned it either....But did You spend any time cleaning the wheels on the engines? They oxidize and get dirty also and with some wheels not touching the rails, it will only be worse for power pick-up. Also check for both trucks picking up power. You can do that by setting it on a piece of powered track and slightly hold one truck off the rails, then the other, to make sure they are both working.
Take Care!
Frank
UPDATE: With turkey running out of both ears, I returned to the work bench. I decided to address the new Dash 8-40C first. Given that the engine was new when I purchased it a couple of weeks ago, I did not clean the wheels at that time. They looked to be in good condition. However, I have no way of knowing how long it had been in the box before I got it. So, I cleaned the wheels per the suggestion above.
I still get both the full stall and the stutter stall but at a greatly reduced frequency. I will assume for now that (for this engine, anyway) dirty wheels are at least a contributing factor if not the cause of the problem.
I also tried lifting each set of wheels as per above and still got intermittent stalling. Not really sure what that means because I know that at least one wheel on each side of the "in contact" truck was touching the rail. I believe that constitutes an electrical connection/circuit and current should flow to the decoder/motor/drivers unless my understanding of the process is flawed.
I also placed a thin sheet of paper on the track and drove the locomotive over it. For the most part, it continued to run until all wheels lost contact with the rail. However it, too, ocassionally stalled after the first truck was completely on the paper.
I will clean the wheels again as thoroughly as possible, check the results and report them here.
I will also be addressing the older loco with the obvious "truck tilt" and report those results in a day or so.
Thanks for your help so far.
P.S. Would it be helpful to have video of any issues from this point forward? I can record and post to Youtube if necessary.
Rusty Railz,
I thought maybe an N-scaler would have by now, chimed in.
Anyway...You can post a video if You'd like..but not really necessary...being there in person would be better.
To Me it still sounds like a power pick-up problem and to add to what was already suggested.....the power pick-up wipers...Have You done anything to them? Are they all touching the back of the wheel face? Do the wheels have that blackening on them? It's said that does not hurt electrical pick-up, but I have My doubts, especially on wipers I have some BLI engines that had pick-up problem's until I removed it. Pick up a can of CRC 2-26 and spray some on all Your contact points. Make sure the little red plastic nozzle is on the can when You purchase it, makes getting at small places easier.....What it looks like:
http://www.homedepot.com/p/CRC-2-26-5-oz-Multi-Purpose-Lubricant-02004/100398344
One More thing I would also try...is to put the engine on blocks, under each end of it with trucks not touching anything and with alligator jumper wires from test track to input of decoder and try to go through all the functions of running on Your tracks with Your controller, If everything works properly....You definitely know it's a pick-up problem.
Good Luck, again.
Thanks for hanging in there with me, Frank. I completed my more "thorough" cleaning of the wheels by running the loco while each truck rested on a paper towel soaked with denatured alcohol.
The stalls still occur, but now only in specific locations on the track. I deem that a track issue until proven otherwise and will correct it.
I did a test similar to the one you describe using the jumper wires a couple of days ago when I first posted to the forum. I didn't have the engine blocked in an upright position but, rather, placed it on its "back". All functions worked correctly.
As to the wipers - this Bachmann loco does not have wipers that touch the wheels. Instead, the metal axle of each set of wheels makes contact with a small copper strip that, in turn, makes contact with the frame. The strip-to-frame contact is not a very large surface and, to my mind, not a satisfactory arrangement. I tried to address this in another engine, but have not been pleased with the results.
I am now considering soldering a small strip of copper to each strip-to-frame to increase the surface area of contact and slightly increase the pressure of the contact. I'll let you know how that turns out.
I also am going to attempt repair of the older loco with the obvious "wheels in the air" syndrome. Not sure how to approach that yet, but I'll be working on it the next couple of days.
Well, after a brief trip to Santa Fe, I addressed the older of the two locomotives again - the one with the "wheels-in-the-air" syndrome. It turns out that my problem was two fold.
"Wheels-in-the-air" was part of it and it took a great deal of finagling to resolve that issue, but it is now resolved.
The second part involved the wipers (as described in a previous post). I can thank Bachmann for this one - not bad-mouthing them, it's just how it is.
There was a minute (and I do mean minute - less than a millimeter) gap that would occur when the loco was started (due to torque, maybe?) and that disrupted power. Then the loco would "untorque" and make contact again, try to move forward/reverse, lift again, stall, etc. I have resolved that by bending the wiper to make better contact and will monitor my solution as I use the engine. May have to construct some sort of replacement or better engineering if it re-occurs.
My thanks to all who suggested solutions, everyone was at least partially right and helped me look in the right places to get things working again.
Happy Holidays!
Sounds like Your on the right path!
I don't care for those electrical contact wipers either. I never cared for Bachmann equipment. But in all fairness....I do have three 2-8-0 Spectrums that I've had from the mid-90's that run like swiss watches.
Glad You hung in there!
Take Care, ''Happy Holidays'' To You also!