Loco Won't Run In One Direction (But Sound Still Plays)

[That Model Railway Guy]

Hi folks, I’m having a weird issue with a Zimo sound decoder that I’m hoping someone might be able to help with. It’s the MS490R which I’ve hardwired into a loco on a Kato 11-109 chassis.

 

In reverse it runs absolutely fine (including sound) but when wanting the loco to go forwards it doesn’t move at all. Meanwhile, the sound will play the drain cocks as usual but then jumps to the exhaust beat with the chuff at an incredible high speed - all while the loco is completely stationary.

 

The loco doesn’t show any sign of moving in this direction and with the sound turned off there’s no indication that the motor is struggling or trying to move. It’s as if there’s no power being applied.

 

Previously the loco was hardwired with a non-sound Zimo decoder and was absolutely fine with that. When I first switched over to the sound decoder I added a stay alive as well so the first thing I did was the remove that in case I’d installed it incorrectly and that was causing problems - that hasn’t made any difference though. I’ve also checked all my wiring to make sure nothing is causing a short and everything is how it should be - as far as I can see, everything is fine. I reset the decoder as well but this also had no effect.

 

Finally, I removed the decoder entirely to run the loco on DC analogue (just to check it wasn’t an issue with the loco/motor itself) and it runs fine in both directions.

 

I’m a bit stumped to be honest but not being too experienced with sound installations (I’ve done a few but not many) I wonder if there’s something obvious I’m missing? It just seems odd to me that, the loco doesn’t respond at all in only one direction while the chuff still plays - albeit at an alarming rate.

 

The only thing other thing I could think to try (which only came to me whilst writing this) would be to change CV29 and invert the loco direction to see if the issue flips with the CV or remains the same. That means I’ll have to wire the decoder back in so hopefully I’ll have a chance to do that later today.

 

In the meantime if anyone has any suggestions or has come across something similar in the past I’m all ears! Thanks in advance 🙂

[Nigelcliffe]

Try the decoder on a motor (on its own, not in a loco).   If the motor spins both ways, looks like the decoder is working.  If not, decoder has a hardware fault.   

 

Changing CV29 is unlikely to make any difference.  

 

Get back to your supplier quickly - supply of decoders is limited at present, so you need a replacement sooner rather than later.   

 

 

- Nigel

[Harlequin]

There may be an accidental connection between one side of the the motor and raw DCC signal. Check for unwanted continuity paths between the motor contacts and the rails using a multimeter.

 

Edited September 23, 2022 by Harlequin

[That Model Railway Guy]

Thanks for the info guys. Having had another go tonight and trying both of your suggestions it does seem like it's an issue with the decoder itself, which is annoying. Luckily I still have the non-sound decoder to use in the meantime until the one with sound gets sorted by the retailer.

 

 Thanks again for the help 👍

[Neal Ball]

I’ve had this issue with a new Zimo MS decoder…

 

Having done a hard reset a couple of times, it then lost the sound file. It wouldn’t drive or produce sounds.

 

It was replaced…. Although the company couldn’t find any issues…. It came back, only to find it wouldn’t work again.

 

As distance is an issue for me, between the supplier and myself, we programmed everything under instruction and slowly rebuilt the file. Eventually it was fine.

 

Good luck!

[SRman]

I had the same thing happen with an older ESU LokSound decoder. It was determined to be a decoder fault. I was able to trade it in on a newer version LokSound.
 

For the Zimo decoder, can you (the OP) try it in a different locomotive?

 

[RAF96]

Similar uni-directional problem was seen on some early TTS decoders. This extended to programming as well as running in that all was well if the loco was facing say left but not if it was facing right. A reload with later firmware by Hornby fixed it. Something to do with the decoder reading the rail A-B signal OK but not the rail B-A phase.

Edited October 8, 2022 by RAF96

[Ruston]

I've got this problem right now, with a Zimo MS500 that I have just installed.

 

The loco will only run in one direction and pressing the reverser button on the handset it is hit or miss as to whether the reverser sound plays or not. When it does go into gear it sometimes refuses to move and goes silent, or will begin to move but stops and the reverser sound plays without me pressing the button on the handset. A further issue is that even when it moves in the one direction that it will move in, there is sometimes a period of several seconds before anything happens. I don't mean the inertia, I mean that there is no movement or the start of the moving sounds.

 

I know it's not a mechanical problem with the locomotive as it ran well in both directions on DC and I have also swapped the orange and grey wires over on the motor with this decoder.

 

I phoned the supplier and was told to reset CV8 to 8, but this has had no effect. I'll be phoning again, tomorrow, and no doubt will have to send it back.

 

I don't know about anyone else here but out of over 30 installations of Zimo MX series decoders I have had just one failure but out of about 8 installations of MS series I have had 3 inexplicable failures that are not as a result of mishandling or incorrect installation. A friend has a similar number of MX with just one failure and 10 MS with 3 failures. This suggests that there's something wrong with Zimo's new decoders.

[Stefan88]

Zimo have had big problems sourcing microchips lately and have had to resort to using different types than they otherwise would (and reworking the PCBs to accommodate these), I wonder whether this could be related.

 

The only issues I've had with my MS decoders has been the sound loading - several of them required many attempts to get the sound loaded as it kept breaking off saying there was an error. One of them didn't even work fresh out of the box and needed a few goes uploading the latest firmware using the powercycle feature to force it through as everything else was suggesting the decoder was dead. I got all of them working and loaded in the end and haven't had any issues thereafter. These were all MS450P22, MS440 & MS580s, so no wired versions.