Peter, how old is the set? There is a very common and well-known problem with Locos from older production that have been left sitting in storage for several years untouched. Items from the 80's onward seem particularly susceptible whereas you almost never get it on items up to the 70's.

HOS or hardened oil syndrome where the oil virtually evaporates leaving behind what is almost glue. Everything becomes bound and seized. Your symptoms match perfectly what usually happens. "All the lights are on but nobody's home". Sometimes if you watch very carefully with the body off, when you alternately drive and reverse the loco you may see very tiny movement in the armature or some of the gears as it tries to turn.

Don't try this for more than a few seconds or you risk burning out the armature or decoder. Also, do not attempt to turn the wheels by hand.

There are two options. Full strip, clean, lightly lube and reassemble is what many people will tell you.

Personally, I have many times been able to restore Locos to operation by gently manually turning the gear train until the bound gears and wheels start to work free and they become progressively smoother.

To answer your main question, you'd expect to see voltage on those wires when running up to around 16v.

But First thing I would check is side to side movement of the wheels. There should be a small amount of lateral play and very often you will find one or more wheel set quite free to move and others with no movement. That gives you a comparison to start with. Slightly increasing sideways pressure on the frozen wheel-set will often be enough but it will help to put the tiniest drop of oil into the bearing/axle to help. And of course be careful of the coupling rods, valve gear etc not to bend anything.

The gears themselves can usually be "encouraged" into movement with a non-metallic object like a piece of hard plastic, or even your fingers to work free without scratching them.

As the drive-train works free you will see increasing rotation by drive, reverse, drive etc as the Loco comes back to life. Again smallest drop of oil of the gears will help.

This can save you having to strip the engine and having to get solvent to clean all the parts, some of which you still can't remove anyway such as the wheels and gears. You may prefer to do the strip & clean but getting it working will at least prove you are on the right track. Or you may find that it runs well without any stripping in which case regular use will be the best thing.

It may also help to warm the Loco up a little, wrap in a cloth and place on or near a heater for a few hours, maybe a hair-dryer etc to soften the oil resin. I know this to work from comments on other forums.

Hope this helps.

Steve

The question was which voltage goes FROM the decoder mounting board. ( Green and blue wires to the motor. )

With lights and sound working, the voltage going TO the decoder mounting board,
from whatever controller Peter is using ,is not relevant, since it's obviously OK

Per.

Yes - and no

If you measure the voltage as an average, the voltage changes according to the speed.

But since in reality the output from the decoder is a PWM-signal, the peak voltage is always the same,
only the on / off interval timing is changing

At full speed the voltage is 16 V pure DC.

Per.

Hi

The loco used to run.Not too many hours on the system +/-10 hours. the motor is free and turns. The loco was starting fast and then slowing down to the desired speed as per the conttroller. the strange this is that when the speed is turned up on the station 2, the train does not move and the loco sounds stay at a stopped setting. no matter how fast the speed is set.

Thanks Per, I thought later on that it would be something like that, not that I'm an electrical engineer like yourself (not even a pretend one....)

This puzzles me.

Can you turn the lights and the sound off and on?

If you can, I don't know what is wrong

If you can't, I think you have a digital communication problem, e.g wrong address setting.

Usually the loco sound should change to driving sounds, even if the motor or the decoder output for the motor is defect;
but I don't have this loco, so I'm not 100% sure.........

Per.

One of my BR003 locos [ with DCM ] started to run sluggishly. I could not see anything wrong so took the brushes out and wiped them on a clean cloth. After Fitting the brushes again, the loco ran fine. This comment may be relevant even though my loco was analogue.

Dereck

I once measured the voltage of the motor output of 6080 decoder and found it to be -5 to -15V. Can't recall if I was using a proper meter or if was averaging.

Visualization can be seen at https://cabin-layout.mixmox.com/2007/07/voltage-visualization.html