Hornby X7170 motor problems

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My Hornby H Class was running perfectly until I ran it today.  It would only move a inch or so before stalling.  I tracked the problem down to the Hornby X7170 motor.  Brushes checked and found to be ok. I removed the motor and ran it without any load and noticed that it would run for about ten seconds before slowing and coming to a stop.
Any ideas anyone?

Thanking you.

Terry
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Sorry, no idea.
 
It might be useful to have an ammeter in series when you run it without load to see what the current draw tells you over those 10sec or so.

Unusually high then dropping, or normal then gradually dropping. Then someone with more experience with motors might have a better idea with more data to hand.




 
 

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Hi Terry,

DC I presume. Do you have another controller, or even a 9v battery? Do other engines behave the same?


Nigel

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Thanks Colin and Nigel.  Sorry, I forgot to mention that it is running on DC.  Other locos do not behave in the same way.

 Lying in bed this morning I had a bit of a brainwave moment.  The loco had a previous owner and it never occurred to me that he may have fitted a DCC decoder and if so, it may be this which is the problem and not the motor.

Question 1 - How do I tell the difference between a decoder and a blanking plug? (Is that the correct name?)

Question 2 - Assuming it is fitted with a decoder and I want to replace it with a blanking plug, do I have to obtain a plug appertaining to this particular model (H class), or is one plug the same as any other with the same number of pins?

Thanking you.

Terry

Last edit: by col.stephens

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Hi Terry,

that depends of how the model was supplied originally.

1) If it was sold as "DCC ready" then there will be a socket to accept a DCC chip with suitable no.of pins.

2) If DCC was fitted after buying a model with no socket, then a Chip will be directly wired in between power pick up lines from track, and the motor. Red and black lines to chip; Orange and grey wires going from chip to the motor.

In case 1) you have 2 choices, pick the easier.

Find the correct blanking plug OR
cut off the socket leaving the wires from the track (Red/ black) and to motor orange/grey.
de-solder the wires attached to motor, not required.
Add extensions to the red/ black leads so they'll reach to the motor lugs and solder on to run

In case 2 you have only this option

cut the red and black input leads in between the chip and  start of the leads, leaving some on the chip to either sell or use  later. Likewise for Orange and grey, easiest just to de-solder these off  the motor lugs.
Add extensions to the red/ black leads so they'll reach to the motor lugs and solder on.


PS if something is sitting in the DCC ready socket it will either have a short stub of plastic protruding a few mm long at most;. no DCC chip is that small. Anything longer then would be your chip, this is a small one.top 4 wires being the DCC power leads described above.




 
 
Good luck

Colin

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Thank you Colin, very kind of you to post such a detailed reply.
I have had a look under the body and a blanking plug is definitely fitted.  So, the mystery remains - why does the motor start and come to a stop shortly after?  Surely the motor would either run normally when power is applied or not run at all when power is applied.  But to run for a few seconds and then stop is baffling.

I think that I may have to completely remove the motor from the chassis and apply power directly to it to see if it performs normally.

Terry
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Hi Terry,

My pleasure.

That sounds like a plan!
 
I had a similar situation, dug out my deerstalker hat and ended up working all the way back finally to removing the motor. Then by noting the current drawn under no load of any sort it was clear where the problem lay as it was about 4 times what you'd expect. Some sort of internal but non fatal short or a faulty bearing are my guesses in my case.

Yours may well be different so nailing it down will be a process of elimination of each variable, one step at a time.

You could then check for free movement in the drive train once the motor is disengaged. How much friction on a slope? I'm sure others may have more specific guidance which may help with this as I've no idea how freely it should run.

Last edit: by Colin W

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Hi Terry,

Blanking plugs Usually have 4 pins in the  case of an 8 pin or 6 pin decoder. The aim is to short grey/black and orange/red so power gets to the motor. if the model was originally DC then the previous owner could have wired in a socket rather than hard wired it.


Easy enough to tell - do the wires from the pickups go to the motor, or to a small circuit board? If the latter it should have red/black in from the motor and orange/grey to the motor so bin the board and socket and solder the pickup wires to the motor. I had this issue once, faulty circuit board with a loose wire that shorted red/grey. If there is a decoder installed it's a lot bigger than a blanking board, and will usually be covered in plastic (with 6 or 8 wires connected to the socket).


When you say you tested the motor, does this mean you removed the motor or just applied power directly to the terminals? If the latter, remove all wires and test.


If the wires go directly to the motor then it's probably a short in the motor or the RF suppressors. If they're still there bin them, as nobody has valve radios or TVs these days. A dirty commutator with lots of carbon between the segments will cause shorts especially if the previous owner used oil to lubricate the bearings. Try cleaning it with a cotton bud and acetone. Armature windings can get brittle with age and cause shorts when hot.

Does you controller indicate a short?


Sounds like a wiring issue, a faulty decoder if installed, or a duff motor. This motor is known to be a bit iffy. Try a new one if you can find one.


Nigel

Edit: Black to grey. Depending on wire supply or the phase of the moon you might find some funny colors used - anything from all black to all red from the pickups. My bet is on the commutator. One experience I had recently was a very tiny screw trapped in the armetures that jammed the works when current was applied. If you have current flowing and a jam the motor will quickly turn into a one use toaster.

Last edit: by BCDR


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Thank you Colin and Nigel.

 Definitely fitted with a blanking plug.  Very small with no wires attached and with 'DC' printed thereon.

When I tested the motor the wiring and TV suppressor were still attached.  My plan is now to remove these.  Not very difficult as they are soldered to a thin 'washer' with a tag and is easily removed.

I have checked the carbon brushes and cleaned the commutator.  The controller does not show a fault.
If the motor proves to be ok I am thinking in terms of running wires direct from the pick-ups to the motor terminals, just like we did in the old days!

Terry

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Hi Terry

I had a Hornby B12 that did this - on some occasions it took up smoking!!

I returned it to Hornby Service Centre who tracked the fault to the on-board PCB (it was DC with no chip)

The repair was done free of charge but I was happy to part with the £20 that they quoted initially.  They agreed to do it free because RMWeb was seeing plenty of comment on this problem with this class.

Might be worth giving Hornby a call - I found them very helpful

Barry

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Something easy to test, drawing from Barry's post, is to pull out the blanking pin and reinsert it ensuring it makes good firm contact. It might just be something as simple as that! The problem could also possibly be with a dry solder joint on the wired side of the socket or board giving intermittent contact

The latter would require you to remove the DCC socket to test / fix / direct wire, so better talk to Hornby before resorting to that.

Colin
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Hi Terry,

Wot I sed in post 8.  Loose wire at the back of the board, usually the result of a poor soldering job. As you're DC bin the plug/socket, hard wire the pickup wires after testing the motor to make sure it has life.

Nigel

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Hello Barry, Colin & Nigel.  I have only just caught up with your recent posts on this thread as I have been distracted by other modelling projects.  Thanks very much. I shall be giving the loco some more attention soon. 
Terry
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Further to the previous entries in this thread.

On further investigation I came to the conclusion that the motor was faulty.  No problem, just install a new motor.  That's when I hit another problem.  That particular Hornby motor, which includes the worm gear and flywheel, is unavailable at present.  I tried all of the usual dealers of Hornby spare parts and nobody has one.


I then contacted Hornby, and to cut a long story short, they very kindly fitted the loco with a new chassis, free of charge.  Excellent service - thank you Hornby. 

On giving the newly refurbished loco a run on my layout, it kept derailing at the joint between two facing points.  I noticed that the ends of the rails were slightly offset so gave them a tweak with the pliers.  Unfortunately this didn't solve the problem, which now appeared to be something to do with the weight of the loco shifting towards the rear half, causing the front driving wheels to lift off the track.

I remembered reading somewhere that this balance problem is common to 0-4-4s and that the solution is to pack weight over the front drivers.  Off came the body to reveal that there isn't much spare room at the front as the flywheel is situated at the front of the boiler.  However, the body moulding includes a hollow dome and chimney.  The dome is situated just in front of the rear driver.  This was filled with lead shot and a strip of double-sided sticky tape, which was all I had to hand, was stuck inside the boiler to cover the dome and base of the chimney.  The chimney was also filled with lead shot and a plug of Das clay added on top to seal it.  When dry this will be painted black.

The loco was test-run on the layout and the small amount of extra weight at the front appears to have solved the problem.

Terry


Last edit: by col.stephens

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