Intermittent running after decoder fitted

[racingpete]

I converted a Hornby J94 a few days back to DCC using a zimo budget decoder (first attempt so was keeping it cheap)

 

When testing it it would start and then stop, then maybe start again and stop again. I tested the volts across the motor and when it was stopping it had no volts hitting the motor (so makes sense it would stop).

 

I then checked the voltage across the pickup wires connected to the decoder, they were dropping to zero also at the time it stopped.

 

I then checked at the wheels itself (not the pickups) and they would drop to zero when it stopped also.

 

So I put the loco on a rolling road and checked the voltage and the track was constantly sending current to the loco wheels.

 

I have cleaned the wheels and it didn't make a difference, so wondering if it is the pickup or this is something that is set wrong in the decoder?

 

Also if the decoder had some cut off or something would that affect any of the pickup circuitry (ie the wires or at the wheels)?

 

The other factory fitted DCC locos run fine and I have resoldered all connections in case it was that. Help please.

[Crosland]

If there is no voltage all the way back to the wheels then what about the track?

 

Are you sure the system is not shutting down due to a short in the loco?

 

A very simple indicator can be made from a couple of LEDs wired in parallel, but opposite polarity (i.e. anode to cathode and vice versa) in series with a 1K resistor.

 

[Normal multimeters will not give accurate measurements of DCC but for simple volts/no volts they may be OK]

[racingpete]

The track has voltage, around 11.2 on my NCE Power cab, that stays constant at either track or the rolling road when using it. When the loco cuts out it still shows 11.2, so issue is isolated to loco.

 

Would the decoder have separate short capability?

[racingpete]

I have fitted an LED on function 1 now to see if that suffers the same issues, which it does. When the train stops the LED goes out and after a nudge of the train it starts moving again but the LED stays off. It turns back on once the F1 is turned off and on again.... Till the train stalls again.