I recently put a Digitrax DZ123 decoder in my Bachmann 44-tonner. Before I put the decoder in, it ran fine and was quite zippy for its size. For about a week it ran normally with the decoder, but now it won’t go any faster than about 20smph at full throttle. I’ve checked the CVs on the decoder (even done a full decoder reset) and popped the shell off the loco to make sure all the joints were properly lubricated, solid electrical connections, etc. I also checked the track voltage, which is correct, and I haven’t had this problem with any other locomotives I’ve put decoders in.
Check the voltage coming from the decoder itself. If it’s low the decoder is the problem and needs to be replaced. If not the problem is the loco itself. Disconnect the decoder from the motor and run the motor directly from track power. If your DCC system can’t run a DC loco run it on a test track with DC power.
Is your loco the two motor or the single motor version? I had a two motor version that showed the same symptoms and finally stopped altogether and fried the decoder (a DZ123). It turned out that one of the motors for some reason developed a high current draw which continued to get worse until it failed. I now have a single motor version again with a DZ123 that runs very well. I would recommend checking the current draw of the loco and if it’s OK I would try another decoder to rule out a decoder failure.
Mine is the single motor version. I’ll have to check how much current it is drawing. I’d rather not have to buy another decoder but if that’s what’s wrong, at least it’s an easy fix.
OK, if you did a reset to factory default on the Programming Track, and the problem persists, send that decoder back to Digitrax and let them figure out the problem. Sounds like a defective decoder to me.
It may well be the decoder. I’ve had a few do what the OP described. But, and this is a BIG but, it could be the loco itself. I had a P2K PA1 that had me scratching my head. It run fine before I put a decoder in it and it ran fine for quite a while afterward. Then one day it just took to running slow. Gotta be the decoder I thought so I changed it out and it still ran slow. So I disconnected the decoder and ran the loco on straight DC on a test track and it just poked along. Turned out something on the locos board had gone key-flooey and the motor was getting only a fraction of the power it needed. So I put the decoder back in and connected the motor directly to the decoders motor wires and didn’t have another problem with it. The OP could have a bad decoder, he could have a bad board (if the loco has one) or the loco could have a bum motor. Best way to check the motor theory is to disconnect the decoder and run the loco on a test track using a DC power pack or some other DC power source. Do not attempt to use the NCE system for this! It could fry the loco.
I agree with you Jeff and, of course, that was your earlier suggestion to the OP. Remove the decoder and run the loco on a DC track in order to rule out the loco as the culprit.
(wow 6 months later I’m just now working back around to this issue)
Did just that and it looks like the decoder wa. In fact the problem. I’ve contacted Digitrax, hope to hear back from them soon.
I don’t think anything I did would have caused this problem? I looked at the wiring before discinnecting the decoder and everything seemed to be in the right place.