Britannia Builder Posted February 2, 2017 Share Posted February 2, 2017 I rather rashly dismantled the tender of my DoG TTS because I'd noticed that one of the pickups wasn't touching the back of the wheel and I wanted to bend it back into place. Unfortunately after reassembly it did about half a lap and then stopped with a short circuit. It now causes a short within a couple of seconds whenever it's on the track - the sound does start up briefly. I've dismantled again to inspect it and check the wiring. The resistance across the motor is about 40 ohms which is probably OK, but the resistance across the driving wheels is only about 5 ohms which is clearly wrong. If I unplug the decoder there is no continuity across the driving wheels, so the wiring from pickups to decoder socket is presumably OK. I've examined the decoder and its wires under a magnifying glass and can't see anything amiss, but the problem must be in there somewhere. Any ideas on what I can do to pin the problem down? Regards, John Link to comment Share on other sites More sharing options...
96RAF Posted February 2, 2017 Share Posted February 2, 2017 Check the decoder pins are not protruding into the socket such that they touch the chassis.If so lift the socket and insulate the chassis With tape.whilst the socket is out check no tracking between socket connections pin hole to pin hole. Link to comment Share on other sites More sharing options...
Britannia Builder Posted February 2, 2017 Author Share Posted February 2, 2017 Thanks Rob. I've checked the decoder pins and they are well clear of the chassis. I've also checked that there's no continuity between contiguous wire attachments on the circuit board. I've disconnected the socket between tender and loco and the problem still occurs with just the tender on the track (it has pickups on two of the axles). When switching the power on there's a low hiss from the speaker which continues until the power trips after about 5 seconds (so it's not a dead short circuit). If I turn on the TTS sound, that also starts to come through the speaker so the board is producing sound correctly. The resistance across the speaker connections on the board is about 7 ohms, which I guess is correct. It looks as though the board may have blown, but I can't think why. Regards, John Link to comment Share on other sites More sharing options...
Rog RJ Posted February 2, 2017 Share Posted February 2, 2017 You could check that the tender wheels are all the right way round. I think there should be an insulating bush on one side of the axles but not on the other side and all the bushes should be on one side. Which side they should be on, I don't know. Link to comment Share on other sites More sharing options...
Britannia Builder Posted February 2, 2017 Author Share Posted February 2, 2017 I didn't take the axles out, so that won't be the problem. It must be something on the circuit board or its wiring harness. Could the board have been damaged by electrostatic charge from my fingers? And could that cause it to draw too much current, rather than just stopping it from functioning? I guess I'll have to get an ordinary decoder to replace it and abandon the TTS sound for the time being. Regards, John Link to comment Share on other sites More sharing options...
2e0dtoeric Posted February 2, 2017 Share Posted February 2, 2017 Did you buy the Duke new? As you have voided the guarantee by dismantling it, I'd look at the pick-up wiper that wasn't touching before. Perhaps someone else put that particular set of wheels in backwards, and cheated by bending the wiper away from the wheel.As it (presumably) worked before you 'repaired' it, the repair has to be the fault. Link to comment Share on other sites More sharing options...
Britannia Builder Posted February 2, 2017 Author Share Posted February 2, 2017 Yes, I bought it new from Hattons about 9 months ago and it worked very well even with the bent wiper so I really should have known better. I obviously won't attempt to claim under warranty since I've dismantled it. I did remove the tender body from the chassis, although that turned out not to be necessary since the wipers are accessed by removing the plate underneath the axles. The only thing I did to the decoder was to refix the sticky tape holding down the wiring which had come unstuck, and I probably touched the circuit board while doing so. It's odd that it did run halfway round the track after reassembling before the short circuit first happened. Regards, John Link to comment Share on other sites More sharing options...
Fishmanoz Posted February 2, 2017 Share Posted February 2, 2017 They cannot void a warranty because you correctly tensioned a pickup on a wheel, this is standard maintenance practice described in the documentation. So if less than 12 months old, you can take it back under warranty. Also, while its possible to damage a decoder by electrostatic charge handling it, I would suggest this is unlikely. I'm with 2e0 on its being something more mechanical you did in tensioning the pickup, so you should check around that again from track to decoder looking for shorts or high resistance paths that shouldn't be there. Link to comment Share on other sites More sharing options...
Britannia Builder Posted February 3, 2017 Author Share Posted February 3, 2017 Thanks Fishman, I've dismantled it all again and the wipers etc look OK (incidentally the wheels are insulated from the axles at both ends in this particular case). I've taken out the speaker and that looks fine. There's no short when the tender is on the track without the decoder, but as soon as I touch the decoder pins into their socket there's a gentle hiss from the speaker and the eLink trips after about 5 seconds. I've tried it on the programming track but all the CVs come back as 255. The sounds, eg the long whistle, do work in the brief period before it trips, so it's no completely dead. The hissing suggests to me that the track voltage is getting through to the speaker somehow, and I did think that perhaps one of the wipers was touching a speaker terminal, but I've now established that it can only be through the circuit board as I'm testing it with the speaker and board away from the chassis. There's no sign of physical damage or overheating on the board, examined through a strong magnifier. I wonder if it will be possible to get a replacement DoG TTS board? It's not one of the ones that Hornby have announced (I have A1 and Class 47 boards on order). Regards, John Link to comment Share on other sites More sharing options...
Howbi Posted February 3, 2017 Share Posted February 3, 2017 BB.........have you tried the TTS decoder in a different loco?.........any with an 8 pin socket will do.......HB Link to comment Share on other sites More sharing options...
Fishmanoz Posted February 3, 2017 Share Posted February 3, 2017 Certainly seems to be the decoder. Putting it in another loco as HB suggests will prove it. Again, take it back under warranty if less than 12 months old, Hornby will have a spare decoder for it. Ring Customer Care from the Contact Us phone number at the bottom of this page. Link to comment Share on other sites More sharing options...
Britannia Builder Posted February 3, 2017 Author Share Posted February 3, 2017 I think I might wait a while before opening up another loco! I've emailed Customer Care with a link to this thread so we'll see what they come up with. Regards, John Link to comment Share on other sites More sharing options...
pendeenpete Posted February 3, 2017 Share Posted February 3, 2017 Hi, have you got a dcc blanking plug that will fit,that will prove if you have done anything wrong,or as stated the decoder is misbehaving. Just a thought Link to comment Share on other sites More sharing options...
Fishmanoz Posted February 3, 2017 Share Posted February 3, 2017 Emailing HCC has an average reply time of weeks, if at all. I did say ring them for a reason. When you ring, I would only mention that you retensioned the pickup on the back of the wheel, don't go through the full rigmarole on here. Link to comment Share on other sites More sharing options...
Britannia Builder Posted February 7, 2017 Author Share Posted February 7, 2017 Hi Fishman To be fair to Hornby Customer Service, they have replied to my email in less than 2 working days and asked me to send the loco back to be looked at under warranty. I did refer to this thread in my email, so they have the full picture. Very good service. Regards, John Link to comment Share on other sites More sharing options...
Fishmanoz Posted February 7, 2017 Share Posted February 7, 2017 You've done well Bb and, once returned to them, they have a good record of fixing things. Link to comment Share on other sites More sharing options...
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