Hornby class 47 TTS running problem

[125_driver]

I am having some trouble with a class 47 tts from Hornby. All of a sudden it began running strangely  it moves for about 2 seconds, stops, then moves for another 2 seconds ,stops, and so on. The stopping is in a regular consistent pattern, unlike when it is dirty wheels etc. 

 

My first thought was decoder issue, so I reset it to factory settings but to no avail. I then sent the decoder to Hornby believing it faulty but when they replaced it with a brand new one the problem has persisted and does so when I fit a DCC blanking plate.

 

Does anyone have any suggestions what is at play here?!

[RAF96]

Does the motor stop or is it a gear train problem.

[Chrisr40]

Have you also checked wheel backs not just the treads ? 

Does the motor run consistently if you apply power directly to the motor terminals ?

[125_driver]

4 hours ago, Chrisr40 said:

Have you also checked wheel backs not just the treads ? 

Does the motor run consistently if you apply power directly to the motor terminals ?

Right i think I've managed to sort it,  I have adjusted a pickup that wasn't quite touching a wheel properly and that seems to have cured things. Just seems strange as generally when poor supply is the issue the stopping is usually more inconsistent in nature whereas with this engine it was very consistent  , move for 2 seconds and stop, move for 2 seconds and stop. Anyway , fingers crossed that's solved the problem, thanks for the replies....

[125_driver]

So this loco is continuing to give me headaches. 

The strange thing is it runs fine after a few minutes , but for the first few minutes of running time, it runs for a couple of seconds, stops  then runs, stops, and yet after a few minutes it runs perfectly. 

This Is all totally regardless of track cleanliness, wheel cleanliness, pickup cleanliness etc. 

I have tried everything , including changing the decoder. Its almost as if the motor needs to warm up before it will run properly. However I haven't had this problem with any other Hornby tts 47s. 

Any ideas what could be the problem here???

[MikeParkin65]

13 hours ago, 125_driver said:

So this loco is continuing to give me headaches. 

The strange thing is it runs fine after a few minutes , but for the first few minutes of running time, it runs for a couple of seconds, stops  then runs, stops, and yet after a few minutes it runs perfectly. 

This Is all totally regardless of track cleanliness, wheel cleanliness, pickup cleanliness etc. 

I have tried everything , including changing the decoder. Its almost as if the motor needs to warm up before it will run properly. However I haven't had this problem with any other Hornby tts 47s. 

Any ideas what could be the problem here???

You've eliminated the chip as an issue (by swapping it) so I'd go for an issue with the DCC socket (maybe a bad solder joint) or power supply to the motor (damaged wire?). 

[125_driver]

3 hours ago, cbrooks122000 said:

Hornby TTS decoders are extremely susceptible to a bad signal, more so than the normal Hornby decoders. So a bad pickup may well explain your issue.

I have checked the pickups etc very carefully. What i find most strange is it is absolutely fine after a couple of minutes. And the stop start is extremely rhythmic, it isn't haphazard as one normally finds with poor running. 

[125_driver]

1 hour ago, MikeParkin65 said:

You've eliminated the chip as an issue (by swapping it) so I'd go for an issue with the DCC socket (maybe a bad solder joint) or power supply to the motor (damaged wire?). 

I will check the wiring again , but would bad wiring be something that would only affect the loco upon its first few minutes and then suddenly start running normally? However I will check it again  , thanks for the suggestions .

[MikeParkin65]

48 minutes ago, 125_driver said:

I will check the wiring again , but would bad wiring be something that would only affect the loco upon its first few minutes and then suddenly start running normally? However I will check it again  , thanks for the suggestions .

I am wondering if something expands when its warmer and that perhaps explains the events. 

[paftrain]

3 hours ago, MikeParkin65 said:

You've eliminated the chip as an issue (by swapping it) so I'd go for an issue with the DCC socket (maybe a bad solder joint) or power supply to the motor (damaged wire?). 

I had the exact same problem with a Hornby WC, and when I ran it with the body removed I could see the motor ‘arcing’ i.e. flashing, so I have purchased a replacement motor. Have you tied running it with the body off? You will soon see if the motor is faulty.

[RAF96]

I would lift the socket and after closely inspecting for solder tracking across pins or the odd stray wire, apply a bit of insulation tape under the socket (although this may not be necessary if the mount is to a plastic chassis.

Try distorting the 8-pin plug legs as some plugs and sockets have a poor interference fit creating odd power down. Your symptoms suggest a loss of power and periodic decoder reboot. Does the sound reboot or does it keep going and just the motor fails.

Edited June 7, 2021 by RAF96

[125_driver]

I shall try all of the above suggestions as soon as I get a spare moment. 

Many thanks for all the help ! Will report back.

[125_driver]

So this loco is turning into a real dog. Decided to have another look with some of the suggestions above, however after running for about 3 minutes the decoder blew. I also noticed the motor was very hot, not sure if that was caused by the decoder or vice versa. So more time in the works for this one I think.....

[Tim123]

If possible put a blanking plug into the loco putting back to DC power only, and place an ammeter in series with the output of a DC controller. On either an oval if track of a rolling road the loco ought to pull around 100 milliamps running on its own. Any momentary draw of over 500 milliamps will cause the decoder to shut down. Long-term draw over that figure will cause permanent damage. TTS decoders don't have overload protection that some others do.

[Tim123]

Further thoughts - the motor getting hot is a result of a defect / failure point in the motor. The all plastic motor housing dismantles without any tools, it’s all “snap together” plastic tabs. Replace the motor with part X9674. It’s advertised as fitting the class 37 which uses the same internal housing and gears. However you will need to solder the motor feed wires. At the same time I’d remove the suppression capacitor as it plays no part when a decoder is used.

 

If you have another non sound decoder, say a standard Hornby one, test the loco using that. Once satisfied fit a a replacement TTS decoder.

[RAF96]

On 07/06/2021 at 21:22, Tim123 said:

. . . motor current draw . . . TTS decoders don't have overload protection that some others do.

 

Incorrect statement. TTS decoder have self protection on the motor circuit but not on the function outputs. Overloading the functions can shut down the decoder due to total current draw and may damage the functions.

 

As Colin states a capacitor across the motor that shorts will kill the decoder. Some such capacitors can be difficult to spot.