Loss of power

[Black5]

Evening all,

I have a Hornby 2-6-4 tank loco that has recently had a spell of intermittent running on dcc. After removing the bottom plate and checking everything was clean and pickups were making contact it went back on the track but there was no movement.

I removed the decoder ( thinking I may have blown it ) and checked the running on my test track,using it in dc. Still no movement.

On checking various things I`ve found the following,

All wiring and pickups appear to be in place but there isn't any power to the motor when picking up from the track.

With a blanking plug in place, the motor doesn`t run even when power is applied to the motor terminals direct.

Remove the blanking plug and again with power to motor terminals the motor turns.

Could it be that on dismantling for the clean up, I `ve lost some sort of insulation which is now creating a short circuit.

The loco drive axles have what look like thin nylon spacers between the back of the wheels and the chassis and these are all in place.

 I`ve come to a grinding halt now as I`ve looked at everything I can think of and wondered if anyone recognises my fault from my description.

I`m sure the answer is simple but I`m darned if I can see it at the moment.

 

Many thanks,

 

Jim.

 

[The Johnster]

You should be able to check for a short using a multimeter, and even a really cheap one will do fine for this job.

 

Your fault is a mystery to me as well from your description, sorry, but if you can prove that no short circuit is taking place, it may be worth your while looking for a mechanical reason for the loco's reluctance to move.  We know that the motor is working, and with the multimeter we can prove connection from the track to the motor via wheels, pickups, circuit board, and connecting wires.  Once that is done, and it is established that there is no electrical problem (if you find one, then the fault finding diagnosis has been completed, of course) then remove the motor and push the rolling chassis gently along with your finger.  You will quickly establish that it is running freely, and where it is sticking if it isn't running freely.  

 

You may have a gear meshing problem, or motion jamming, or any number of fouling issues, but it clearly won't be something obvious as you'd have already spotted it.  If you still haven't found the problem, put the motor back and turn the armature by hand until a full revolution of the driving wheels has been accomplished without jamming or fouling anywhere.

[34theletterbetweenB&D]

...I have a Hornby 2-6-4 tank loco that has recently had a spell of intermittent running on dcc.

 

After removing the bottom plate and checking everything was clean and pickups were making contact it went back on the track but there was no movement.

 

With a blanking plug in place, the motor doesn`t run even when power is applied to the motor terminals direct.

 

Remove the blanking plug and again with power to motor terminals the motor turns.

 Thiose four extracts tell the story.

 

Intermittent wiring fault caused intermittent running.

 

On dismantling it, wiring fault was made permanent.

 

The fault is a short circuit somewhere between the decoder plug and the pick ups

 

The motor is fine, so it is just a matter of correcting the wiring fault causing the short. As above a test meter will be helpful.

[Black5]

You should be able to check for a short using a multimeter, and even a really cheap one will do fine for this job.

 

Your fault is a mystery to me as well from your description, sorry, but if you can prove that no short circuit is taking place, it may be worth your while looking for a mechanical reason for the loco's reluctance to move.  We know that the motor is working, and with the multimeter we can prove connection from the track to the motor via wheels, pickups, circuit board, and connecting wires.  Once that is done, and it is established that there is no electrical problem (if you find one, then the fault finding diagnosis has been completed, of course) then remove the motor and push the rolling chassis gently along with your finger.  You will quickly establish that it is running freely, and where it is sticking if it isn't running freely.  

 

You may have a gear meshing problem, or motion jamming, or any number of fouling issues, but it clearly won't be something obvious as you'd have already spotted it.  If you still haven't found the problem, put the motor back and turn the armature by hand until a full revolution of the driving wheels has been accomplished without jamming or fouling anywhere.

Many thanks for your reply.

I should have said that I`d removed the motor and gear drive to eliminate any sticky movement and that is fine. One thing I`ve noticed is a wire coming up through a hole in the chassis which I think is an earth to the motor. Some of this wire is bare and I`m wondering if some insulation  has moved and the wire is touching the chassis causing a short. Of course it may have no bearing on the problem at all but I`m going to sleeve it and see what happens. Thanks once again.

[Black5]

 Thiose four extracts tell the story.

 

Intermittent wiring fault caused intermittent running.

 

On dismantling it, wiring fault was made permanent.

 

The fault is a short circuit somewhere between the decoder plug and the pick ups

 

The motor is fine, so it is just a matter of correcting the wiring fault causing the short. As above a test meter will be helpful.

Thankyou for your reply. You`ve helped me before. As I said to The Johnster, I`ve found a wire that maybe should have some insulation on it passing up through the chassis to the motor. On reassembling my checks it could be that this wire is touching the chassis and causing the problem. It`s my next point to look at. Thanks once again.