Soundtraxx MC1 OEM (probably) headlights not dimming

[D869]

Some time back I acquired a Dapol 'N' Western listed as a near non-runner via a certain auction site.

 

On investigation I noticed a blue shrink wrapped thing in the DCC socket. Most of my running is on DC so I took it out, fitted a blanking plug and the loco ran just fine.

 

I'm now getting ready for some photos and it would be nice to be able to be able to have the lights on with the loco stood still so I put the decoder back in and hooked it up to my NCE Powercab. Everything worked more or less as expected but the lights are too bright. The speed control is rather non-linear but I don't need it to move so I'm not bothered about that just now.

 

Powercab reports the manufacturer and version as 141 and 081, which as far as I can gather means ThrottleUp(Soundtraxx) / OEM MC1. I have no idea if this came from Dapol or was fitted by a previous owner.

 

I got hold of the manuals. These suggest that F7 will dim the lights by a fixed amount... but there is no noticeable dimming when I press '7' on the Powercab.

https://www.soundtraxx.com/manuals/MC1 Users Guide.pdf

https://www.soundtraxx.com/manuals/MC1 Tech Reference.pdf

 

I did a CV reset by setting CV8 to 8 and powered the whole thing off and on just to be on the safe side.

 

The manual says that the F7 behaviour is controlled by CV41 and its default value is 16. Mine was zero even after the CV reset. I tried 16 but that didn't help.

 

I also tried setting CV38 to 128 (it was also zero) which should put dimming onto the F4 button so the function state is displayed on the Powercab LCD, but again no joy.

 

All of the CV setting is done in Direct Mode which is supported according to the manual.

 

I also checked CV49 which is something to do with selecting lighting effects. This was already set to 1 which I think is what it should be for dimming. There is a bunch of US lingo in the manual here about grade crossings and Rule 17 so I can't really figure out what this CV is supposed to be set to but 1 seems most likely.

 

Does anyone have any idea where I might be going wrong? Have I identified the decoder correctly? Can it even do dimming?

 

I did manage to sort out the dimming on my CT equipped Farish D800s but so far this blue shrink wrapped decoder has not been persuaded to dim its lights.

 

Thanks in advance.

Andy.

[Nigelcliffe]

One of the various Bachmann badged 6-pin decoders is a re-badging of a Soundtraxx MC decoder.   Its probably that one.

[D869]

55 minutes ago, Nigelcliffe said:

One of the various Bachmann badged 6-pin decoders is a re-badging of a Soundtraxx MC decoder.   Its probably that one.

 

Thanks Nigel. So probably not original to the Dapol Western then. I'm somewhat comforted by that because although it does run adequately with this decoder I'd expect a good deal better out of the box from a factory fitted decoder.

 

I do wonder whether the seller knew the decoder was in there or had acquired it like that. I dont think there was any mention of it having a decoder in the listing so it may be that he was trying to run it on DC. It certainly did run very badly indeed like that.

 

I don't think I'll be spending much more time on this decoder. I might try one of the CTs in the loco once we are done photographing.

 

Regards, Andy

[Nigelcliffe]

These days, I'd not spend the extra on a CT over cheaper alternatives such as the £20 Zimo.   Only case for the CT is either extreme space constraints very unusual small

motor types where CT's control might differ from Zimo's.   Neither likely to be an issue on a typical N bogie diesel.   Of course, if you have one already in stock then use it.

 

The Soundtraxx decoder can be improved,  the motor parameters for KPI settings are needed to adapt it to the motor (CV's numbered 200-and-something).  The speed curves have an extra CV to enable them to work (because there are some pre-packaged curves in Soundtraxx decoders).  But I'd not expect an end result up at CT or Zimo running qualities.     

 

I'd be more cautious in expectations for "factory fitted decoders" - they a mixed quality in my experience from "old stock of antique rubbish" to "near state of the art".  

 

 

- Nigel

 

[beejack]

16 hours ago, D869 said:

The manual says that the F7 behaviour is controlled by CV41 and its default value is 16. Mine was zero even after the CV reset. I tried 16 but that didn't help.

 

I've taken a look at the decoder definitions for mc1 in Decoder pro and they only seem to look for either a value of zero or one for the dimming on CV41.

[D869]

Thanks both. The photo sesh is done now but I'll have another play with the Western when I've got everything back in their proper places again.

 

@Nigel I do get the feeling from other posts on here that the 20 quid Zimos are well regarded and plan to get hold of one to try out next time I am in the vicinity of a DCC trader's stand at a show. In the short term all of the decoders will be coming out of all of the the locos so it will be easy enough to try out a CT in the Western and find out whether it does better. I'm aware that the MC1's back EMF parameters can be tuned to the motor but the chip seems pretty basic in other ways so I'm not sure it's worth the effort.

 

I do have some previous history that colours my views on this. I bought a TCS back emf decoder PCB that was purpose designed for the Atlas MP15 chassis in my class 22. I never could get on with driving it and my efforts to try to tune the CVs couldn't make it right. In the end I fitted a 6 pin socket and the CT does a really good job in that loco too.

 

Regards, Andy

[D869]

I tried a '1' in there but that didn't help.

 

I also tried a CT in the Western and it ran just fine. The MC1 has a step upwards in throttle response around step 11 or 12. Maybe fixable but life's too short. The throttle response was smooth when I fitted the CT decoder.

 

Thanks again for your help. The MC1 will be taking up residence in the bottom drawer along with the TCS board for the MP15.

 

Regards, Andy