UPDATE: My 2MT won't stop

[signalmaintainer]

UPDATE: Please see my third fourth post!

 

I put a new Digitrax DZ125PS into my new Bachmann Ivatt 2MT today. I'd tested the locomotive on DC earlier and it ran very smoothly and quietly (very little PWM-induced "buzz.").

 

It runs quite well on DCC also -- except at times the locomotive will not stop. Although I have the throttle wound down to '"0", it continues to creep along, especially as it approaches the end of a track. This is with address 03 and CVs 2, 3, 4, 5 and 6 at 000. I've reset the decoder to factory defaults several times, and continue to get the same odd behavior.

 

Also, on the way out to the visible portion of the layout, it will put on burst of speed once it leaves staging. Again, none of my other locomotives behave this way. In the middle of the layout, none of these odd characteristics are evident.

 

I thought I might have a base station or a throttle problem (I have a Digitrax Empire Builder system), but ruled that out as all my other locomotives are performing just fine. Some are Digitrax decoders, some are TCS. I then installed a slightly used DZ125PS in the Ivatt -- and I still get the same results.

 

I'd heard that Digitrax has had problems with decoders in recent years. Could I have stumbled upon a bad batch?

[Mr.S.corn78]

Hi,

 

have you removed the supressors (orange things) from the motor as I have fitted a few chips to this type and I have found removing them has helped.

 

Also if the decoder has BEMF it may also be causing a few problems. Try changing the settings if you are able too.

 

Hope this helps

cheers

Simon

[signalmaintainer]

Hi Simon,

 

I did remove the capacitor and the small chokes from the adapter plug. Doing do resulted in the adapter plug no longer being able to function as intended, so I've had to hardwire the decoder.

 

A BEMF issue arose in my thought as a possibility as well -- this during the wee hours of the morning when the matter was still on my mind. Thanks for the lead, as I'll pursue it!

[signalmaintainer]

I've disabled the BEMF function on CVs 55, 56, and 57 to take them out the equation. And a second throttle is not involved or even connected.

 

Still have the same problem, though: the locomotive will not respond to the throttle setting while on any of the staging yard tracks (other decoder locos, no problems). It continues at the same speed and will not slow down. And when reversing toward the visible portion of the layout, it crawls along until it reaches the transverser, which is on an isolated (albeit still DCC, of course) track circuit; then it suddenly speeds up to the throttle setting -- except. ...

 

... when there is another decoder-equipped locomotive on the same staging track, then the mysterious loco responds to the throttle! Somehow the digital packet information from the booster is not reaching the mysterious loco except in that circumstance.

[signalmaintainer]

UPDATE:

 

I found a solution: I replaced the DZ125PS with an older DN121 cannabalized from an HO locomotive. Problem solved.

 

So that's two brand-new/almost-new Digitrax DZ125s that didn't work properly in default factory setting mode.

 

Might be time to switch to a Lenz or NCE system and decoders, methinks.

[M Graff]

You have to disable the DC operation in CV 29 to make it stop misbehaving, I had a DZ 125 that started creeping by itself as well until I disabled DC on it.

[signalmaintainer]

You have to disable the DC operation in CV 29 to make it stop misbehaving, I had a DZ 125 that started creeping by itself as well until I disabled DC on it.

 

That seemed a possibility to me, except it would only misbehave (not stop even though the throttle was a 0) at the end of a dead-end track, e.g., at the station terminus or on a staging track. Otherwise no problems.

 

I can see how disabling DC would be a possible solution though. I've got a Black 5 (great runner but a bit too big for the theme of my layout) that could use a chip. I'll put the DZ125 in it and dial CV29 to 2, taking out the DC mode.

[AllScales]

Wow, I've had the same problem with a DZ125IN in a ROCO HOe engine, it would crawl along, then suddenly speed up once it got into the neighbourhood of the power feed. Once up and running at maniac speed the only way to make it stop was to use the use Panic button.

 

I've set CV 29 to 2 and presto! I can stop it... This running with a ROCO multiMaus. It is still a bit rough on speeding up and slowing down and the minimum speed is a bit off, but at least it reacts now.

 

Now all I have to do is to bend all six pins without breaking them so I can put the roof of the cab back on (on thereby save £35 over the ROCO "ripoff" decoder). Then I need to do the same for my Mh6...

 

Next challenge: Has anyone managed to get a Hornby R8216 Points decoder to work with a ROCO multiMaus system? It's got me beat.....

[AllScales]

I've disabled the BEMF function on CVs 55, 56, and 57 to take them out the equation. And a second throttle is not involved or even connected.

 

It looks like I spoke too soon. I've disabled DC mode (never had to do this with a Lenz), and it works, as long as it's the only loco on the track. As soon as you introduce a second (even if motionless), it's back to square one.

 

Even if you remove the second loco from the track when the new one is running you still can't stop it. It will only listen properly if there's nothing else on track when it's first told to move off!

 

I've tried to have a look where I can find the various meanings and value descriptions of the CV's for the digitrax decoders? I have a manual for the Lenz decoder, but it doesn't mention BEMF functions, those CV's seem to be for headlight brightness, and function mapping...

 

Thanks

[signalmaintainer]

A few weeks back I swapped out the DN121 with the new DX125PS, dialed in CV29 to remove any analog (DC) control, and everything is hunky-dory now. My 2MT runs like a watch.