markSandD Posted October 14, 2011 Share Posted October 14, 2011 I recently purchased a 'Bachmann 7F', and as it requires a 21 pin Decoder, I bought and installed a Hornby Sapphire. All went well with the installation.The loco was run for an hour in both directions, to run it in.The issue that I am having is that the loco is very 'jerky' especially at low speed, is there something I can do to alter the settings of the decoder to try and combat this? I dont have this problem with any other locos on my layout, and I have made sure that the tracks are clean. Link to comment Share on other sites More sharing options...
Phil_Spiegel. Posted October 18, 2011 Share Posted October 18, 2011 It MIGHT be the default setting of the back-emf is not the best settting for your loco: different motors are best with different settings ... this is why they are 'adjustable'.Therefore try changing the CV controlling 'back emf' to OFF and see if it makes a noticeable change. If it does, then when you turn it back on, you'll have to try various values for the 2 adjustable parts of the back-emf setting.Another option to consider with the B locos, is the removal of the supresion capacitors mounted across the motor nd to the chassis .... but if adjusting the backemf CV values cures the problem, this is the easier solution. Link to comment Share on other sites More sharing options...
Gregd99 Posted October 18, 2011 Share Posted October 18, 2011 I have had what sounds like the exact same problem with a class 20 hornby loco. setting the back-emf cutout to 0 transformed a jerky loco into a smooth running machine:-) Link to comment Share on other sites More sharing options...
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