phil Roberts

Hi UPDATE I know it's a bit late in the day but for those asking the question did I cure the jerky running? Yes.... I took the plunge and removed the suppression components i.e. L1, L2 and C1 as detailed earlier and now all four of my 68's run absolutely smooth as butter so many thanks to whoever it was that suggested it. They're so different.

Update..... the new Dapol 21 Pin decoder arrived today and was duly installed with.... 99% success. Mid range is now a lot smoother so apparently there is a difference between two decoders of the same make. Both v4. However I say 99% because it is still slightly jerky and I mean slightly, so decision time. Either break the warranty and remove the suppression components or live with it. I’ve decided to live with it for the time being as it’s not so noticeable now with a five coach loading. Knowing me though I won’t be happy until it’s perfect. thank you all for sharing your knowledge and experience, it’s been an enjoyable learning curve. Phil

Hi Mark, posts must have passed mid flight . Thank you for confirming which components are which especially when mine was a guess. At least I have a fall back plan now should the new Dapol 21 pin (expected Tuesday) fail to match. What I have gained from these discussions is the realisation that removal of the suppression capacitors is common practice. Had no idea.

Hi Ixion. Have attached a cleaned up copy of the cct board As requested. As you say guessing which components do what is not really best way forward. I’ve spent some considerable time unsuccessfully searching the internet to see if anyone else has experienced this and also if anyone knows which are the capacitors in question. I’ve already ordered a new Dapol 21 pin in the hope we get a match, if not I have a choice of playing around with BEMF parameters Of either the Dapol or Lenz neither of which fill me with hope as both have limited information available. Thank you

Update....... with the above comments on suppression components In mind I fitted the suspect Lenz decoder into the existing old 68 and it was still jerky but no where near as bad and the Dapol decoder which had similar jerky characteristics in the New 68 actually came from the original 68 so we know it runs fine in that. It’s looking like the theory above is the answer, finding the right decoder for the right machine. Alternatively remove the suppression components as suggested. I’ve attached photo showing with purely a wild guess what might be the components in question. Can anyone confirm?

Thank you all for your comments. The general consensus seems to point towards the suppression components which I’m glad to admit is all new to my decoder knowledge so I’ve not missed the obvious. Being low spec I guess two cards by the same manufacturer could give different results. Now the big question (and I apologise if it seems I’m being spoon fed) does anybody know where these components are in a class 68? I’ll also try the suggestion to install the suspect decoders in the good 68 just to prove the theory above. thank you again

Andi, no idea on that sorry. It does work ok with the borrowed ESU sound decoder though so I guess proving the loco is not at fault.

It's my third class 68 but is very jerky mid range. I've tried to approach this problem methodically so here goes. It's runs problem free on DC. Have a Lenz and Dapol decoder spare and both behave the same. Slow and full speed are ok it's only mid range. I know it's something to do with back emf but not sure how to modify or sample this on either of these two decoders. I transferred an ESU with sound from my other 68 and that worked fine. So any advice on how to resolve EMF on either of these two chips would be welcome.