Stuttering train on DCC

[Litninbolt]

So I have a loco that is stuttering on the track, if I give it slow or fast throttle with Digitrax, makes no difference.
was ok few days ago…puzzled..I leaned on the track power connection screw a little, no difference.

it’s a Piko factory DCC camelback loco new.

 

[PhilP]

Clean the tyres (treads) of the wheels..
Clean the skates (if fitted)..
Make sure they move up and down freely..
Does the Piko use carbon brushes on the rear faces of the wheels? - As LGB loco's do?? If so, clean the rear face of the wheels..

PhilP

 

[Neil Robinson]

Clean the tyres (treads) of the wheels..
Clean the skates (if fitted)..
Make sure they move up and down freely..
Does the Piko use carbon brushes on the rear faces of the wheels? - As LGB loco's do?? If so, clean the rear face of the wheels..

PhilP

If that doesn't sort it clean half your track. Check if the cleaned section makes any difference to the performance.

 

[Greg Elmassian]

Lay it on it's back and apply power and see if it stutters... isolate between the track pickups / dirty track, / connections first..

apply power right from your DCC supply.

If it keeps stuttering, you need to investigate the loco... if not, try a short length of track separately powered..

Greg

 

[Litninbolt]

That’s a great idea, grabbing my alligator clips!,
Thanks

 

[Greg Elmassian]

The fastest way to debug a problem is to "cut it into pieces"...

The classic lawnmower that won't start example:

remove spark plug:

wet - ignition system problem
dry - fuel system problem

that first test will eliminate debugging one entire "path"

Greg

 

[Keith RhB]

If none of the above work for you, try reducing the voltage to the track. I’m assuming you can adjust the output voltage like I can on my Massoth system. I’ve seen this exact problem before with a brand new Piko loco that a friend brought over to troubleshoot on my track. It didn’t like the higher voltage (22.5V say) on my track, and it stuttered and wouldn’t run right. Once I reduced it to around 19V it was just fine. The decoders Piko uses can’t handle the power...

 

[Greg Elmassian]

Voltage...

That is weird, since that means they do not meed NMRA standard.

I did look up the manual, and indeed Keith is on to something, the decoder is an OEM by Soundtraxx and the large scale Tsunamis all fail to support the NMRA DCC voltage per the standard.

I have used and tested quite a few, actually from the first days they were available (years ago). The Tsunami family will go into overheat or overvoltage mode at 19-21 volts DCC. Operation I have seen is erratic, or the damn thing just stops with lights blinking.

What I would do is first, if you have an accurate way to measure DCC track voltage, it would be good to confirm that, but again I think Keith is right on the nose.

I would not turn down the track voltage (why punish other locos that meed NMRA standards) but put a "voltage dropper" in the loco one one if the "track pickup" sides.

This is a simple and inexpensive circuit to reduce the DCC voltage without interfering with the signal quality.

here is one assembled in a manner to make the wiring clear, it can be made much more compact:

This particular circuit drops six times 0.7 volts, or 4.2 volts.... this would drop a system that put the maximum NRMA standard of 24 volts to 19.8 volts, but very few systems put the full 24 volts DCC on the rails.

Every diode you "add" the the "chain" reduces dcc voltage 0.7 volts....

This has the added benefit that no matter whose system you run this loco on, it will not go into shutdown.

Misc. electronics

Greg Elmassian web site on large scale trains and garden railroads, cigars, and computers

elmassian.com

Greg

 

[1to3]

You can do coversions, or install devices to limit power to your loco if you want, but it is likely the power system.
Just in case, check your power supply to see if it is, in fact, 27V or less. (Power in DCC needs specific equipment, not just a multi-meter.) With DCC many brand systems add in more power. Some say 20V-24V but once power waves are calculated out you will likely get peaks far above that!

NMRA standards say decoders should shut down at 27V - to protect the circuitry. SoundTraxx follows that standard to the letter.

Below is info I got from a power expert...
"Many times a 22VDC power supply with DCC is sending more than 27V. (Multiply 22 times the square root of 2, or 1.414.) Many power supplies send re-modulated power with a digital alternating current wave form, so the square root of 2 factor would make sense. That’s something over 31V.) A volt or two can be lost by system circuitry and possibly over distance, but based on the math it is possible there is still well above the equivalent of 27V on the rails."

I am guessing this is why Piko switched their digital system to a 6A/20V power supply a few years back! (When calculated out, It is pretty much the same amount of power as 5A/24V - what they used to use - but the 20V configuration is within the NMRA specs.) And yes, I do use the Piko digital system and many brand locos... they work just fine.

 

[Dan]

I am fortunate enough to have a system that can control the output track voltage anywhere from 12 volts to 24 volts (Zimo) and running these decoders that do not fully comply with G scale NMRA specs are not a big issue. However saying that, I do not own any of these decoders, I just do this to test club engines I repair. On another note, if one buys the Zimo 20 amp system, you can set the 8 amp programming output for HO and the 12 amp output for G scale and use just one system to run both scales.