Yesterday, I decided it was time to try my first retrofit of a DC loco that didn’t involve a plug in decoder. I’m always a little nervous opening up a loco especially when it involves the electronics but I have a number of old DC locos that still run well and are begging for decoders. I decided to do as simple a retrofit as I could. I have a Walthers doodlebug (no longer available) and grabbed a 4 function Atlas decoder. I figured a doodlebug would have plenty of room inside and doesn’t have the bells and whistles associated with steam or diesel locos so this seemed like it couldn’t be any simpler.
The first obstacle was opening up the darn thing. Of course I no longer have the instructions but how tough could it be. I gently pried the sides hoping the frame would drop out. No luck. Didn’t budge. I looked closer at the bottom and saw two screws on the front end which I removed and the only thing that happened was the pilot fell off. I then proceeded to go around the whole body gently (sort of) prying with the small screwdriver. Eventually, I worked it free with the only damage being the windows popping out on one side. An easy fix.
First I had to remove the seating section which is made of metal and doubles as the weight. Undereath, i discovered two long wires connecting the front and rear wheels and there were jumpers from the front wheels to the motor and headlight. After figuring out what wires need to go where, I cut the long wires in two so I could attach them at opposite ends of the decoder per the Atlas instruction sheet. I also cut the motor jumper from the front wheels and the headlight jumper from the motor. I was relieved to see the Atlas decoder had plug caps which meant soldering wouldn’t be necessary, not that that was going to be a huge issue. Attaching the small wires to the decoder was a bit tricky for my ham hands (How do you N-scale guys do it?). In the process, I broke the soldered connection to the motor and had to get out the soldering iron
Was the Doodlebug running smoothly before you put the decoder into it? Are the wheels and track clean? No decoder will improve a poorly operating model; in fact, if a model doesn’t run smoothly without a decoder, you’re just wasting your time putting a decoder into it. It sounds like you have a power pickup problem with the wheels due to dirt or a loose, sporadic connection between the wheels and the decoder.
It ran well on my DC test track and also ran well on the DCC layout running on address zero. After those test runs, I parked it on a siding and forgot about it and have had some brief operating sessions since when it was receiving constant track power but those were very brief sessions. If there is something wrong with the motor, it almost certainly would have been due to the exposure to the constant track power although I have left other DC locos on the track longer than this one without damage. I will have to rewire it to its original configuration and run it on the DC test track to see if I have done any permanent damage to the motor.
Some older DC motors are more susceptible to damage from the DCC power than others. I had this happen with an old Model Power switcher. It ran good for a little while, then the motor went up in smoke. Upon opening the motor, it looked like the brushes had almost been welded to the commutator and the heat burned out the windings.
I tried installing a sound decoder in the tender of a Spectrum light 4-8-2. Worked fine, but to do it, I had to remove the weight to gain room. The engine ran very poorly after that, if at all. I took the decoder and speaker out and reinstalled the weight, and put in a Digitrax non-sound decoder. It’s run great ever since, one of my best performers.
Sounds like in this case, reinstalling the weight wasn’t the problem, but it could be something just as (seemingly) minor. I haven’t tried converting my Walthers doodlebug yet, but it’s always been a good runner on DC so I don’t see why it should have trouble with DCC.
(p.s. sometimes these things can be really odd. My Spectrum 2-6-6-2 runs great with the decoder I have in it, I’ve tried putting other decoders in it and it runs poorly, jerking along and sometimes stalling. I have no idea why, the decoders are basically the same, but it likes “it’s” decoder and nothing else will do!!)