TTS chip in EWS 67003

[Chrise]

I installed a class 66 Tts decoder and speaker into my EWS limited edition Class 67003 the first one I needed to modify the cables to the speaker on. Tested it and it worked sound as well. 

I got the 67 out yesterday put it on the track selected it and it flew away not responding to the controller (elite), I had to use the stop button. 

When I opened up the engine this morning 2 wires from the decoder socket to the decoder had 'blown' and one had almost melted. It was the pink and grey, I have disconnected the decoder not sure what to do next.

help please

[ColinB]

The wires should be orange and grey, but it doesn't matter. It sounds like your motor has gone short circuit. I suspect the capacitor across the motor has gone short circuit or the actual motor has gone short circuit. My class 66's capacitor went the same way. Although it blew up the TTS decoder, I don't remember it melting the wires. If you have a multimeter check out the resistance between pins 1 and 5 of the decoder socket. You should get a reading of about 20 to 30 ohms, I suspect you will get 0 to 4 ohms. So check all the wiring, remove the capacitor across the motor and then test it on DC by removing the decoder (sadly it is probably dead) and putting a DC header into your DCC socket.

[Chrissaf]

Pink isn't a standard decoder colour. Could it be orange. If orange, then orange and grey are the wires from the decoder to the motor and being melted would infer that maybe there is a short across the motor.

 

First thing to do is the remove the decoder and re-instate the original 'Blanking Plate' then test loco again on DC

 

I got the 67 out yesterday put it on the track selected it and it flew away not responding to the controller

 

This is called 'DC Runaway' and happens when the decoder is still getting DCC track power but loses synchronisation with the encoded DCC data signal. However this in itself, would unlikely to be observed if there was a genuine short on the motor.

 

The melted wires might possible be a different symptom. In other words, the wires might have been melted for some time before you observed what you have just observed. I say this because, there have been loads of reports of TTS decoders running very hot, so your decoder may have been running very hot for some time.

 

If the loco runs on DC with the 'Blanking Plate' fitted, then you would be advised to do a 'stall test'. There is a recent thread where a forum member had two Class 66 locos, one was fine the other was not. The faulty one appeared to have a faulty motor that was drawing excessive current. Your issues seem very similar to the other posters issues.

 

Read through the other thread. It gives full details of his observations, the results of his tests and gives a link to the stall test method and the conclusions made regarding his loco fault.

 

https://www.hornby.com/uk-en/forum/class-66-dcc-issue-/?p=1/#post-348479

 

It may be that this motor issue is a manufacturing 'batch' fault and lots of Class 66 /67s are affected.

 

PS - Colin's estimate of 20 to 30 Ohms is I believe a little low for the Hornby Class 66 / 67 motor. The previous thread details indicate that the motor should read 55 ohms or thereabouts and that a reading as low as 20 Ohms would actually be a fault.

[Chrise]

This is beyond my knowledge, who could I send it to to fix it and how much would it cost?

[ColinB]

Ok, do the easy bit then. You see where the decoder is, then remove it. In the socket where you took the decoder from put a 8 pin DC header, there should be one with all your bits for the loco. Then run the loco on DC, NOT DCC. I suspect your DC controller will trip out.

If your loco is less than 12 months old, contact Hornby Customers Services and ask for a return number. Send it back to Hornby for a repair under guarantee. If it is over 12 months old then it is going to be, contact your local model shop and ask them to repair it for you.

Actually contact Hornby Customer Services anyway and ask them what to do, your loco shouldn't fail like that and if they have a duff set of capacitors/motors in locos they need to know about it.

[creilly81]

Something to clarify. The modification you made to the speaker wires- what modification was it and what did you do?

I'm wondering,if you used a soldering iron - that there could be some solder cross contamination across the decoder PCB if you were anything other that precise.

[96RAF]

The generic instructions that accompany TTS retro kits say to extend the speaker wires if required at the speaker end rather than trying to desolder/resolder at the decoder pads. It is just as easy to cut the wires at mid point and splice in suitable extension wires suitably sleeved with shrink tube.

 

Something to watch when soldering around a speaker is that the magnet will attract to your soldoering iron tip. I tape a speaker to the bench to minimise such unwanted attraction.

[Chrise]

I never concluded this. In the end I spoke to Hornby and returned both the decoder to them. About a week later the whole thing was returned, new decoder fitted into the Class 67.

FANTASTIC CUSTOMER SERVICE THANK YOU HORNBY

[Rog RJ]

Great result. grinning