RMweb Gold Harlequin Posted January 27, 2019 RMweb Gold Share Posted January 27, 2019 (edited) Hi everyone, I've got a wierd problem with the Oxford Dean Goods that I recently did a sound installation on. Here. It was running well the other day but suddenly stopped and hasn't run since. I obviously immediately suspected my installation and started testing things. This is what I have found: The Zimo decoder is fine - it makes sounds and will drive another Dean Goods loco when I swap tenders. I tried resetting the decoder just in case the PWM or back-EMF settings were corrupt and unable to drive the motor for some reason. No change. The motor is fine - it works freely when removed from the loco and connected to a 9V battery. It offers no unusual resistance when I twist the spindle by hand. The wiring between motor and decoder is not the problem because I have temporarily tacked wires directly from motor to decoder and yet the motor still does nothing significant *. * When I say nothing significant I mean that the motor does not rotate when the decoder should be powering it but it does twist and buzz slightly every now and then. At this point I'm stumped because I appear to eliminated everything!!! Does anyone have any ideas or suggestions? Thanks, Edited January 27, 2019 by Harlequin Link to post Share on other sites More sharing options...
NIK Posted January 27, 2019 Share Posted January 27, 2019 (edited) Hi everyone, I've got a weird problem with the Oxford Dean Goods that I recently did a sound installation on. Here. It was running well the other day but suddenly stopped and hasn't run since. I obviously immediately suspected my installation and started testing things. This is what I have found: The Zimo decoder is fine - it makes sounds and will drive another Dean Goods loco when I swap tenders. I tried resetting the decoder just in case the PWM or back-EMF settings were corrupt and unable to drive the motor for some reason. No change. The motor is fine - it works freely when removed from the loco and connected to a 9V battery. It offers no unusual resistance when I twist the spindle by hand. The wiring between motor and decoder is not the problem because I have temporarily tacked wires directly from motor to decoder and yet the motor still does nothing significant *. * When I say nothing significant I mean that the motor does not rotate when the decoder should be powering it but it does twist and buzz slightly every now and then. At this point I'm stumped because I appear to eliminated everything!!! Does anyone have any ideas or suggestions? Thanks, Hi Phil, Just because the motor runs when connected to a 9 volt battery it does not necessarily mean it is fine. It might have some shorted turns so that it draws more current than the Zimo can provide. Its magnet may have gone out of spec or separated from the rest of the magnetic circuit - again resulting in a higher current. A way to check this would be to get hold of a meter than can measure up to 10 amps DC and put it between the 9V battery and the motor (no DCC decoder in circuit). Regards Nick Edited January 27, 2019 by NIK Link to post Share on other sites More sharing options...
johnb Posted January 27, 2019 Share Posted January 27, 2019 I would assume that you have checked for mechanical issues. Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted January 27, 2019 Share Posted January 27, 2019 ...The motor is fine - it works freely when removed from the loco and connected to a 9V battery. It offers no unusual resistance when I twist the spindle by hand. The wiring between motor and decoder is not the problem because I have temporarily tacked wires directly from motor to decoder and yet the motor still does nothing significant *. When I say nothing significant I mean that the motor does not rotate when the decoder should be powering it but it does twist and buzz slightly every now and then... This suggests the motor is locked by the drive line. Did the chassis roll freely with the motor removed? Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted January 27, 2019 Author RMweb Gold Share Posted January 27, 2019 Hi Phil, Just because the motor runs when connected to a 9 volt battery it does not necessarily mean it is fine. It might have some shorted turns so that it draws more current than the Zimo can provide. Its magnet may have gone out of spec or separated from the rest of the magnetic circuit - again resulting in a higher current. A way to check this would be to get hold of a meter than can measure up to 10 amps DC and put it between the 9V battery and the motor (no DCC decoder in circuit). Regards Nick Thanks, I will do that. I would assume that you have checked for mechanical issues. Thanks, there may be some tightness in the loco chassis but the motor wouldn't run even when removed from the chassis and just connected to the decoder by flying wires. As I said, it turns freely by hand. Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted January 27, 2019 Author RMweb Gold Share Posted January 27, 2019 Hi Phil, Just because the motor runs when connected to a 9 volt battery it does not necessarily mean it is fine. It might have some shorted turns so that it draws more current than the Zimo can provide. Its magnet may have gone out of spec or separated from the rest of the magnetic circuit - again resulting in a higher current. A way to check this would be to get hold of a meter than can measure up to 10 amps DC and put it between the 9V battery and the motor (no DCC decoder in circuit). Regards Nick The motor, removed from the chassis completely, draws 1.1A from a 9V battery. Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted January 27, 2019 RMweb Premium Share Posted January 27, 2019 That is an awful lot for a motor running unloaded, or even under maximum loading. Does seem it’s shot. No wonder the Zimo couldn’t/wouldn’t run it. Izzy Link to post Share on other sites More sharing options...
Graham Radish Posted January 27, 2019 Share Posted January 27, 2019 (edited) 1.1amp from a 9v battery? they only deliver 500ma, a useful max current of roughly 30ma dont you mean a 110ma burst? Edited January 27, 2019 by Graham Radish Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted January 27, 2019 Author RMweb Gold Share Posted January 27, 2019 (edited) Video evidence: The current measured is higher when the motor refuses to start and somewhere between 1.1A and 0.9A when running - slightly different each time. Edited January 27, 2019 by Harlequin Link to post Share on other sites More sharing options...
Graham Radish Posted January 27, 2019 Share Posted January 27, 2019 What type of 9v battery is it? not a PP3 surely Link to post Share on other sites More sharing options...
RMweb Premium spamcan61 Posted January 27, 2019 RMweb Premium Share Posted January 27, 2019 (edited) What type of 9v battery is it? not a PP3 surely A PP3 will probably source over an amp, just not for very long... https://www.powerstream.com/9V-Alkaline-tests.htm Edited January 27, 2019 by spamcan61 Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted January 27, 2019 Author RMweb Gold Share Posted January 27, 2019 (edited) Photographic evidence of battery circuit: Edited January 27, 2019 by Harlequin Link to post Share on other sites More sharing options...
Graham Radish Posted January 27, 2019 Share Posted January 27, 2019 Blimey im surprised the battery didnt get red hot and blow up lol Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted January 27, 2019 RMweb Premium Share Posted January 27, 2019 If you have to spin the motor to get it to run then this would indicate a winding has failed in some way and has gone open circuit. This would account for the high current draw before you spin it to get it going. At 9v the rpm will be pretty high, so as it spins, once every revolution the open circuit will occur allowing a high running draw reading. I take it you do not have a simple DC controller of any kind. I am sure this would reveal that the motor won’t start without assistance on low volts either, a basic sign of a failed winding. Under these circumstances it isn’t surprising the Zimo can’t run it, nothing will. Best you return the loco, if you can, or contact Oxford about the problem. Izzy Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted January 27, 2019 Author RMweb Gold Share Posted January 27, 2019 If you have to spin the motor to get it to run then this would indicate a winding has failed in some way and has gone open circuit. This would account for the high current draw before you spin it to get it going. At 9v the rpm will be pretty high, so as it spins, once every revolution the open circuit will occur allowing a high running draw reading. I take it you do not have a simple DC controller of any kind. I am sure this would reveal that the motor won’t start without assistance on low volts either, a basic sign of a failed winding. Under these circumstances it isn’t surprising the Zimo can’t run it, nothing will. Best you return the loco, if you can, or contact Oxford about the problem. Izzy Thanks. Yes, having to "bump start" the motor does rather suggest something's gone seriously wrong! Thanks to everyone for pointing me in the right direction - I would never have expected the motor to fail like that but I know what to look for now. Is this sort of failure common? I'll have to see what Hatton's or Oxford say but since I've heavilly modified the tender to hardwire the decoder and fit the speaker and Supercap I'll be very happy to pay for a replacement motor. Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted January 27, 2019 RMweb Premium Share Posted January 27, 2019 If you have to spin the motor to get it to run then this would indicate a winding has failed in some way and has gone open circuit. This would account for the high current draw before you spin it to get it going. At 9v the rpm will be pretty high, so as it spins, once every revolution the open circuit will occur allowing a high running draw reading. I take it you do not have a simple DC controller of any kind. I am sure this would reveal that the motor won’t start without assistance on low volts either, a basic sign of a failed winding. Under these circumstances it isn’t surprising the Zimo can’t run it, nothing will. Best you return the loco, if you can, or contact Oxford about the problem. Izzy Surely you mean "Short circuit"? Keith Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted January 27, 2019 RMweb Premium Share Posted January 27, 2019 Thanks. I'll be very happy to pay for a replacement motor. Maybe you could consider a different motor? The original really shouldn't have packed up this soon. You can still get the slim Mashima motors, maybe one would fit? MHK1024: https://www.ebay.co.uk/itm/Mashima-Can-motors-12v-DC-10-12-16-18-series-/132096509708 Cheers Keith Link to post Share on other sites More sharing options...
BWsTrains Posted January 27, 2019 Share Posted January 27, 2019 (edited) Phil, see here https://www.rmweb.co.uk/community/index.php?/topic/107457-oxford-rail-announces-oo-gauge-gwr-dean-goods/?p=3255818 and many other posts in same topic about motor and drive train problems experienced with this model With the track record of this loco you were lucky to get one that ran well as you did. Others like myself went thru much pain and effort to get to that point. The motor issue might well be totally unrelated to your sound install job. I had a brand new Hornby 0-6-0 loco motor short out during running in (after 20 min) - QC at the Chinese motor factories may not be up to scratch right now Colin Edited January 27, 2019 by BWsTrains Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted January 28, 2019 Author RMweb Gold Share Posted January 28, 2019 Thanks Colin, I was aware there had been some problems reported but I wasn't looking forward to delving through that thread! Your link was very useful, thanks, and showed that melmerby is clearly the expert in these matters! P.S. I know what you mean about RTR locos these days - after I've got this Dean Goods off the workbench I've got a Heljan 47xx waiting to have it's gearbox replaced and sundry small parts fixed back on. Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted January 28, 2019 RMweb Premium Share Posted January 28, 2019 Surely you mean "Short circuit"? Keith No. I have always seen a short circuit as where opposing polarities connect without resistance. Open circuit as where there is resistance of some kind, but only a little, say in this case where probably - it’s all conjecture after all - the enamelling has failed/something similar (the same end result). Not nice whatever. Izzy Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted January 28, 2019 RMweb Premium Share Posted January 28, 2019 I had a motor fail in a Bachmann 08 after just 3 months and very little use. Could not find a reason. Having converted it both body and chassis wise (P4), I was lucky I had spare Mashima 1833 from my O gauge days I could transplant. If you can fit a Mashima as Keith suggests that would be the best bet. Don’t know what people will do when stocks of them finally run out. Decent alternatives in a range of sizes haven’t appeared, and I think are unlikely to. Izzy Link to post Share on other sites More sharing options...
RAF96 Posted January 28, 2019 Share Posted January 28, 2019 There was an online demo of hundreds of these batteries plugged together terminal to terminal and there was enough energy to melt a spanner shorted across the final terminals. In a dead short a battery will give all it has no matter its size. Rob Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted January 28, 2019 RMweb Premium Share Posted January 28, 2019 No. I have always seen a short circuit as where opposing polarities connect without resistance. Open circuit as where there is resistance of some kind, but only a little, say in this case where probably - it’s all conjecture after all - the enamelling has failed/something similar (the same end result). Not nice whatever. Izzy A short circuit is when there is no resistance (or very little) when there should be. An open circuit is when there is no connection, so no circuit, so infinite resistance. Keith Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted January 28, 2019 RMweb Premium Share Posted January 28, 2019 (edited) A short circuit is when there is no resistance (or very little) when there should be. An open circuit is when there is no connection, so no circuit, so infinite resistance. Keith Ah, right. Many thanks, I stand corrected. Always understood it this way, so it shows you're always learning! Izzy Edited January 28, 2019 by Izzy Link to post Share on other sites More sharing options...
RMweb Gold Harlequin Posted February 6, 2019 Author RMweb Gold Share Posted February 6, 2019 Update: I explained the problem to Oxford and they have said they will send me a replacement motor - when the ship gets in from China... 1 Link to post Share on other sites More sharing options...
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