DK123GWR Posted April 17, 2021 Share Posted April 17, 2021 I have just fitted a decoder into a Hornby Hall class. The loco now runs well in a forwards direction, but in reverse shorts instantly without moving. I have checked around the wheels, and there does not appear to be anything fouling the mechanism (such as the infamous track pins). Any suggestions of what might be causing this behaviour? Thanks in advance for any suggestions. Link to post Share on other sites More sharing options...
John ks Posted April 19, 2021 Share Posted April 19, 2021 A photo of the wiring might help Is it an XO4 type of motor If XO4 are both brushes insulated John Link to post Share on other sites More sharing options...
DK123GWR Posted April 19, 2021 Author Share Posted April 19, 2021 9 hours ago, John ks said: A photo of the wiring might help Is it an XO4 type of motor If XO4 are both brushes insulated John It is an X03 or X04 motor (I can't tell the difference) and both brushes are insulated. Link to post Share on other sites More sharing options...
GoingUnderground Posted April 19, 2021 Share Posted April 19, 2021 (edited) Both arms of the brush spring must be insulated on the X.04 motor if the motor is to run at all on DCC as both brushes must be insulated from the chassis. It sounds like the axle with the pinion gear wheel is moving sideways towards and touches the chassis when the worm gear starts rotating in the reverse direction. Normally the insulating sleeve on the insulated wheels has a raised collar on the back of the wheel to stop it touching the chassis. But the collar can decay and if it has that could let the wheel move sideways and touch the chassis. But I would have expected that to show up on DC, not just on DCC. I'd also have a look at the wire pickup in case the movement of the wheels as I described above is enough to nip the end of the wire pickup between the wheel and the chassis and cause the short. Edited April 19, 2021 by GoingUnderground Link to post Share on other sites More sharing options...
33C Posted April 19, 2021 Share Posted April 19, 2021 Is there any slop on the driven axle? Being quite an old model the axle hole can wear oval. Replace block or drill and sleeve? Link to post Share on other sites More sharing options...
DK123GWR Posted April 21, 2021 Author Share Posted April 21, 2021 Having had a chance to try again today, it can't be caused by movement of any mechanical components as the short occurs instantaneously (i.e. before the motor is able to move). Link to post Share on other sites More sharing options...
GoingUnderground Posted April 22, 2021 Share Posted April 22, 2021 11 hours ago, DK123GWR said: Having had a chance to try again today, it can't be caused by movement of any mechanical components as the short occurs instantaneously (i.e. before the motor is able to move). Did you check that the loco worked correctly on DC before you fitted the decoder? Because a short such as you describe should show up on DC. Have you tried moving the decoder to another loco that you know works? If the fault moves then it is a problem with the decoder or the way that you are fitting it. Link to post Share on other sites More sharing options...
DK123GWR Posted April 22, 2021 Author Share Posted April 22, 2021 9 hours ago, GoingUnderground said: Did you check that the loco worked correctly on DC before you fitted the decoder? Because a short such as you describe should show up on DC. Have you tried moving the decoder to another loco that you know works? If the fault moves then it is a problem with the decoder or the way that you are fitting it. Yes, the loco worked on DC. I currently have nothing available to move it into. Link to post Share on other sites More sharing options...
John ks Posted April 23, 2021 Share Posted April 23, 2021 On 19/04/2021 at 17:30, John ks said: A photo of the wiring might help John Link to post Share on other sites More sharing options...
gwrcollet Posted May 3, 2021 Share Posted May 3, 2021 I have had a problem with a Hornby loco will only work in one direction this turned out to be the decoder if turned in opposite direction it would show a short and tip the controller, there is a problem with some of the county motors they run fine on dc and have problems with dcc? it would run for a couple of miniutes and then burn out the decoder it was found that the ampage would spike up to 1.5 amp most decoder are 1amp max rated, could not get new motor so sent back to Hornby for repair. Link to post Share on other sites More sharing options...
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