Update: DC operation of a Decodered Engine

[wm3798]

As most of you know by now, I've built a retro style layout with good old c80 track and power packs.  It's basically loop running, with "blocks" controlled by power routing turnouts mostly.  I'm using it run my growing fleet of retro equipment, complete with coffee grinder sound, flanges you can cut linoleum with, and Rapido couplers. 
But I also have the remnants of my old WM fleet from the Big Layout, and I'm getting the itch to run some of it again.  They're mostly installed with Digitrax decoders, which should be "dual mode" to allow operation on DC, but I'm not sure what the secret code is to set CV29.
I previously posed this question to reinvigorate my Bachmann Dual Mode decoders, which has been successful at CV29=6.  I just tried setting up a recent release Atlas GP35 with factory DCC... might be an NCE board... But I'm wondering if someone could do the CV calculation to tell me how to wake it up.
I set CV29=6, and get the directional lighting to come on, but no motor response.
A little help would be a big help.
Thanks
Lee

[djconway]

Lee give this a try http://www.digitrax.com/support/cv/calculators/

[C855B]

Check CV27. Implemented in some decoders as "brake on DC", so set to 0 if it's not 0.

It also controls a directional sense mode ("asymmetric DCC") that's a bit wonkish to use, but your situation requires CV27=0.

[peteski]

Most (if not all) decoders have DC functionality turned on by default. So, doing a decoder reset: usually writing 8 to CV8 would do whatever is needed to get it to run in DC (dual-mode enabled).  It will also set the short address to 3.

Not sure what you use for DC power, but if it is pulsed, some decoders don't llike that.  Easy and cheap decoder tester is a 9V battery (which provides pure DC).  To test the loco just touch the battery terminals to the wheels (or frame halves if the shell is removed).  That will quickly tell you whether the decoder will run on DC or not.

[Point353]

Not sure what you use for DC power, but if it is pulsed, some decoders don't llike that. 

He appears to have procured a passel of Bachmann power packs:

[peteski]

He appears to have procured a passel of Bachmann power packs:

Never had a chance to test them, but I suspect unfiltered DC output.  The 9V battery test is still recommended before reprogramming the non-working decoders.

[wm3798]

I was able to do the factory reset and get power to the motor.  It would appear that there is some pulsing going on... it very slightly surges in a rhythmic way.  Not stalling and coughing, more of an oscillation of a very subtle nature.
It's certainly not as smooth as the straight up DC engines I run.
I'll try another locomotive to see if I get similar results, if I do, I'll abandon the experiment and see about wiring in a toggle to switch the WM route from DC to DCC operation should the urge arise.
Thanks for the assist.
Lee

[wm3798]

Sampled another engine, got the lights, but hardly any power to the motor.  This after getting a steady murmur from a 9 v battery.
I'll have to do some research to confirm, but the Spectrum Magnum power packs appear to have pulse of some sort.
Yet the Bachmann decoder runs smoothly, and without apparent incident!
Curious!
Lee

[nickelplate759]

I was able to do the factory reset and get power to the motor.  It would appear that there is some pulsing going on... it very slightly surges in a rhythmic way.  Not stalling and coughing, more of an oscillation of a very subtle nature.
It's certainly not as smooth as the straight up DC engines I run.
I'll try another locomotive to see if I get similar results, if I do, I'll abandon the experiment and see about wiring in a toggle to switch the WM route from DC to DCC operation should the urge arise.
Thanks for the assist.
Lee

That surging seems to be a characteristic of every Digitrax decoder I've ever run on DC.  The first time I thought I had screwed up the mechanism some how, went to all the trouble of taking the decoder back out and discovered that the mechanism was just fine without it.
The engines run fine on DCC - but I felt I really needed good running on DC as well I wouldn't use Digitrax.  I haven't really evaluated any other brands running on straight DC.

[peteski]

That surging seems to be a characteristic of every Digitrax decoder I've ever run on DC.  The first time I thought I had screwed up the mechanism some how, went to all the trouble of taking the decoder back out and discovered that the mechanism was just fine without it.
The engines run fine on DCC - but I felt I really needed good running on DC as well I wouldn't use Digitrax.  I haven't really evaluated any other brands running on straight DC.

Let's face it, decoders aren't really designed to do well on DC (especially pusing DC).  After all, IMO that feature is just thrown in - the main purpose of decoders, and the bulk of their design, is to run well on DCC.  It is probably there to try to sway the DC-only crowd to migrate to DCC.   

And a bit of backwards compatibility, and maybe even for testign purposes.   Just like in the computer world, if backwards compatibility is even featured, it is usually very limited in it capabilities, and not much development time is spend on it.

[wm3798]

As long as the current HCD is the domain I'm working with, it's not a big deal.  Even if I end up building another more proto thesis DCC layout, I'll hang onto the door so I can play with the Retro stuff.  Either that or put all of it together in a lot and sell it all lock stock and barrel.

I could, as I said, wire in a DPDT to switch the upper line back and forth from DC cab to DCC... but that's like... wiring...  You know how I feel about that!!

Lee