Jump to content

Funny decoder behaviour... **update**


Recommended Posts

Guys, a curious little problem...

I recently fitted a Gaugemaster DCC25 to a Bachmann S4 switcher but noticed some erratic behaviour.
On 28 speed steps which is what I use on all my locos the S4 moves smoothly on step 1. (After I adjusted SV)
Accelerates fine up until speed step 6 or 7 when the motor seems to labour a little and actually slows until I reach speed step 12 or so when it reaches what seems be it's correct speed.

Now I know that Bachmann US outline locos don't have the best mechanisms but I replaced the DCC25 with a bog standard Hornby R8249 and this issue disappears. The loco was a little noisy but was the same with the DCC25.
BTW, this also happend with a Heljan Class 26 but at the time I put it down to the high current draw that Heljan's are known for.

It's not really a huge issue, I can use the DCC25 in anouther loco, I'm just curious as to what causes it. Could it be a BEMF thing? I no it's not adjustable on either of those 2 decoders but that's all I can think of.

Any ideas...

Link to post
Share on other sites

  • 1 month later...



I've finally got bottom of this issue! This was happening with all 3 of the DCC25's that I own, regardless of make an model of loco they were fitted too. I finally got round to checking

the CV which controls at which speed step BEMF cuts off and low and behold it was set to 25 on all 3 decoders. Step 25 on 255 speed steps equates to 7 or 8 on 28 speed steps so this all seems to make sense! I have no recollection of programming this CV at any stage and I have reset the decoders several times so I'm assuming it's a default setting.


Anyway, problem solved, and if anybody else is encountering this issue this might be something to look at.

Link to post
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...