Any idea what this is?

[Rabman]

So I installed a Digitrax DH-123D Decoder in my green 4-6-2 locomotive.

Isolating the motor was fairly easy. I pulled out the spring pivot point, cut the brass conductor bracket, and the reinstalled the pivot point for the brush.

I picked up the track power where the red wire is from the brass bracket I cut. The black wire track power is coming from the tenders bottom frame.

Grey and orange wires to the commutator brush spring pivot pins. I do need to reverse the two wires to get the direction right. I am aware it can also be done by setting a CV value.

I did connect the headlight to the blue and white wires of the Decoder.

I cleaned the tenders wheels as the brass was quite dirty. I have some more cleaning to do as they are not sparkling. Also I did not clean out the area between the axle and truck. I cleaned the locomotive wheels also a bit, though they didn’t look too bad. More wheel cleaning to do. One pain is the tenders wheels cannot be removed as the bottom casting on the bolsters are peened on, not bolted.

So I suspect I have a power quality issue for a number of reasons.

1) at best the locomotive will crawl erratically.

2) making a humming noise when track power is turned on with zero throttle.

3) need to replace the headlight, it isn’t working. Perhaps I blew the bulb when I soldered a wire to the threaded portion. I do have an LED I can replace it with.

So my action plan is:

1) Get a jumper wire with alligator clips and connect to the rail the tender picks power from to the black wire of the Decoder. See if it’s a tender wheel connection issue.

2) repeat the process with the red wire to connect it to the other rail to see if that’s the issue.

3) pull the motor off the frame to see if it behaves properly.

4) all else fails, modify the motor I received with my mikado 2-8-2 to see if it behaves better. I also have new trucks and wheels for the tender to see if that makes the situation better.

5) disconnect the headlight bulb to reduce power draw.

So I am aware these are forty year old plus motors, maybe the power draw is just too much for the Decoder. I tried measuring the current draw of the motor but my meter only goes to 300mA and it is much more than that I’m sure.

A few points: the locomotive with the motor removed seems to be fairly smooth rolling. The tender does make some rough rolling sounds.

When the loco was hooked up to dc, it didn’t start moving until I put about 60% power to it. This predated my wheel cleaning though. The motor turns freely and smoothly when removed from the locomotive. Spins quite fast. I cleaned up the commutator brushes and plus the axles and pivots of the linkages.

A few questions:

Do you think these are good steps to debug?

Am I missing anything?

Is this ever going to work?

Any idea what the issues could be? As mentioned I suspect it is power or an old motor. Blown headlight bulb.

 

[JazzDad]

... It dropped a linkage off the one side. ...

How prototypical!

 

[trailrider]

Check ebay for a complete set of Mantua Pacific valve gear and side rods. They often pop up. You should also look for the pilot. The plastic cabs are readily available on ebay, but you would have to match the paint color. As far as DCC is concerned, you really need to replace the open-frame DC motor with a can motor. A 20mm diameter or flat-side can motor will fit inside the boiler. You need to test the motor at full stall to determine the decoder. The problem is that you will also have to find a gearbox. Those, too, can sometimes be found on ebay. They were made for the early Mantua steamers. The newer versions are being made with them, but I don't know if they would fit the old chassis. If you find the old gearbox, it should have the worm gear, bronze bearings and endplay washers. You will also need screws that hold the gearbox to the chassis. You can probably find those at your LHS. I had one of those Southern Crescent Mantua Pacifics, but sold/traded it because I don't model that railroad.

 

[Rabman]

Check ebay for a complete set of Mantua Pacific valve gear and side rods. They often pop up. You should also look for the pilot. The plastic cabs are readily available on ebay, but you would have to match the paint color.

I was able to get a new pilot and cab. I also fixed the side linkage with a new rivet.

As far as DCC is concerned, you really need to replace the open-frame DC motor with a can motor.

Does this mean I won’t be able to get the open frame motor to work at all or it won’t work as well as a can? If it’s the former, that would be good to know.

I wonder if anyone knows the current draw on an open frame motor.

 

[Iron Horseman]

When the loco was hooked up to dc, it didn’t start moving until I put about 60% power to it. This predated my wheel cleaning though. The motor turns freely and smoothly when removed from the locomotive. Spins quite fast. I cleaned up the commutator brushes and plus the axles and pivots of the linkages.

That is usually the best diagnosis - get it running well on DC before doing a DCC conversion. That way one knows they are fighting DCC issues rather than mechanical or electrical issues.

A few questions:
1. Do you think these are good steps to debug?
2. Am I missing anything?
3. Is this ever going to work?
4.Any idea what the issues could be? As mentioned I suspect it is power or an old motor.

1. Yes.
2. Test the voltage at the motor with throttle at zero. Help figure out why it is making noise. Sounds like a leaking transistor in the main output.
Hook voltage meter to the motor brushes (decoder output) and watch to see if it is smooth power or not.
Are these tests with the boiler/tender shells on or off?
What is the voltage output of the DCC system? Many are set to 14.5V from the factory so that would blow a 12V headlamp right there. In the old days when I ran light blubs, I used ones rated at 18v.
Between the axle and the tender truck frame. Since you didn't clean them, at least blow them out, then get some electrically conductive lubricant for them. Or use graphite, just be certain all the powder is worked in well as graphite in powder form will burn.
3. Ha! Yes, but depends on how much time/effort/money is to be spent doing so.
4. Looking briefly at mine - I used springy brass wire to go from the axle to the power bus ignoring the tender frame "wire" completely. That removes any issues with electrical contact between the axle and the tender truck frame.
Also note the original design only picks up power from 4 of the 6 wheels.
Get a higher capacity amp meter. Harbor Freight gives away the little red ones from time to time. hook it up and squeeze the spinning motor shaft until it stops. That is the "stall current" of the motor. It will vary from motor to motor.

 

[trailrider]

I have a number of Mantua steam locomotives in which I installed the no-longer-produced Canon 20mm coreless motors, using either the cast gear boxes that came on the older models, or the sheet brass ones sold some years ago by the late Herold Mellor. These have always run great on DC, but, several years ago, I decided I wanted sound, requiring DCC. (My layout is equipped to run either systems, depending on which way the selector DPDT toggle on my control panel is thrown, connecting the layout to either an MRC DC power pack, or an NCE Power Cab.) Because of the cost, I only converted two of my steamers, using a certain manufacturer's decoders. The one locomotive, so far has run okay. The other, however, went through three (3) of the same decoders, including burning a hole in the side of the plastic tender shell! (The hole was patched by the locomotive backshop, so it looks like a steel patch.) Now that manufacturer did replace the decoders, under warranty, but at that point I decided to try a different brand, selecting Tsunami2. In selecting the proper decoder, I decided to check the stall current of the Canon motor. I was surprised ("shocked", pun intended) to find the stall current of around 1.0 amps! I contacted Soundtraxx, and was advised to use their TSU-2200, which is rated at 2.0 amps maximum. Unfortunately, I cannot report the results, as time has not permitted me to install the new decoder. As soon as I can get a Round Tuit, I will do it and see what happens. In the meantime, the locomotive runs fine, having been converted back to DC.

 

[Rabman]

That is usually the best diagnosis - get it running well on DC before doing a DCC conversion. That way one knows they are fighting DCC issues rather than mechanical or electrical issues.


1. Yes.
2. Test the voltage at the motor with throttle at zero. Help figure out why it is making noise. Sounds like a leaking transistor in the main output.
Hook voltage meter to the motor brushes (decoder output) and watch to see if it is smooth power or not.
Are these tests with the boiler/tender shells on or off?
What is the voltage output of the DCC system? Many are set to 14.5V from the factory so that would blow a 12V headlamp right there. In the old days when I ran light blubs, I used ones rated at 18v.
Between the axle and the tender truck frame. Since you didn't clean them, at least blow them out, then get some electrically conductive lubricant for them. Or use graphite, just be certain all the powder is worked in well as graphite in powder form will burn.
3. Ha! Yes, but depends on how much time/effort/money is to be spent doing so.
4. Looking briefly at mine - I used springy brass wire to go from the axle to the power bus ignoring the tender frame "wire" completely. That removes any issues with electrical contact between the axle and the tender truck frame.
Also note the original design only picks up power from 4 of the 6 wheels.
Get a higher capacity amp meter. Harbor Freight gives away the little red ones from time to time. hook it up and squeeze the spinning motor shaft until it stops. That is the "stall current" of the motor. It will vary from motor to motor.

Thanks for all the advice. I did a process of elimination tonight. First checking to see if the Decoder was powered right, would the wheels spin.

So I did my checks but started with supplying power to the red and black wires directly from the track with the wheels elevated. The locomotive ran well.

So I corrected the power feed from the tender and the locomotive ran properly.

But boy is it noisy. I believe it is the tender trucks making all the noise. I have some major work to do on it. My next project.

At least the locomotive is running off dcc and I didn’t need to replace the motor. Once the tender is addressed, I think it will run nicely. I’ll keep you posted.

 

[Rabman]

I have a number of Mantua steam locomotives in which I installed the no-longer-produced Canon 20mm coreless motors, using either the cast gear boxes that came on the older models, or the sheet brass ones sold some years ago by the late Herold Mellor. These have always run great on DC, but, several years ago, I decided I wanted sound, requiring DCC. (My layout is equipped to run either systems, depending on which way the selector DPDT toggle on my control panel is thrown, connecting the layout to either an MRC DC power pack, or an NCE Power Cab.) Because of the cost, I only converted two of my steamers, using a certain manufacturer's decoders. The one locomotive, so far has run okay. The other, however, went through three (3) of the same decoders, including burning a hole in the side of the plastic tender shell! (The hole was patched by the locomotive backshop, so it looks like a steel patch.) Now that manufacturer did replace the decoders, under warranty, but at that point I decided to try a different brand, selecting Tsunami2. In selecting the proper decoder, I decided to check the stall current of the Canon motor. I was surprised ("shocked", pun intended) to find the stall current of around 1.0 amps! I contacted Soundtraxx, and was advised to use their TSU-2200, which is rated at 2.0 amps maximum. Unfortunately, I cannot report the results, as time has not permitted me to install the new decoder. As soon as I can get a Round Tuit, I will do it and see what happens. In the meantime, the locomotive runs fine, having been converted back to DC.

Thanks for the thoughtful reply. See above for the progress I made. I had it running for around 20 minutes quite noisily. Before I run it anymore I will do a good thorough tuneup on it.

Who knows, maybe in the future I may re-power it with a can motor.