philg Posted November 23, 2020 Share Posted November 23, 2020 Banging my head against a brick wall here, so would appreciate some suggestions I have a DCC Concepts ZEN decoder in a Hornby 5-BEL. When I use the decoder with back EMF enabled, it runs fine BUT at around speed step 17 or 18 it lurches to a much faster speed - and no amount of fiddling with vstart or vmax stops it So back EMF is off BUT unless I use a speed table I can't seem to get vmax to control a reasonable top speed - it's usually at the scalded cat end of the scale! When I try a speed table though, a level of 1 for the first speed step also seems to translate to maximum speed, so I have to start with a level of 2 for speed step 1. This is not a crawl though so the start will certainly be spilling champagne!! And now I am out of ideas Thanks for any thoughts. Has someone been here already?? Cheers Link to post Share on other sites More sharing options...
tender Posted November 23, 2020 Share Posted November 23, 2020 Yep, I ditched the DCC Concepts decoder and fitted a Zimo, problem solved. 2 Link to post Share on other sites More sharing options...
RMweb Gold RFS Posted November 23, 2020 RMweb Gold Share Posted November 23, 2020 (edited) I bought a couple of DCC Concepts decoders a few years ago when they first came out. They did exactly the same so it seems the same poor BackEMF algorithms are still being used. Quickly replaced with Lenz decoders which are fine as are Zimo ones. Some older TCS decoders exhibited the same trait. Edited November 24, 2020 by RFS Added "older" for clarity Link to post Share on other sites More sharing options...
philg Posted November 23, 2020 Author Share Posted November 23, 2020 Oh, and I did notice that there is a suppression capacitor across the motor terminals. Or rather, there WAS Removing it seems to have made SOME differenc, but a value of 1 in the first speed step of the speed table still feels like 255!! Link to post Share on other sites More sharing options...
philg Posted November 23, 2020 Author Share Posted November 23, 2020 Hmm - Thanks folks. I'll see what I have in my decoder box of tricks Link to post Share on other sites More sharing options...
philg Posted November 23, 2020 Author Share Posted November 23, 2020 57 minutes ago, tender said: Yep, I ditched the DCC Concepts decoder and fitted a Zimo, problem solved. tbh this is an old ZEN so maybe things have got better but I switched it out for TCS DP5 and it's like night and day! Thanks a TON for pointing out that my problem was likely to be THE decoder rather than what it was installed in. I'd kind of assumed that every decoder would at least get the basics right! Over the years I've accumulated decoders from all sorts of places. I think now is the time to standardize Thanks again Link to post Share on other sites More sharing options...
RMweb Gold RFS Posted November 23, 2020 RMweb Gold Share Posted November 23, 2020 55 minutes ago, philg said: Over the years I've accumulated decoders from all sorts of places. I think now is the time to standardize. I got into that position a few years ago, and thought the then new range of DCC Concepts decoders was the answer having read all the hype. I had a number of TCS decoders that had the mid-speed jerk, and was dismayed that the DCC Concepts decoders did exactly the same. Seemed to have very similar firmware. Tried Lenz Standard+ decoder and every loco I used it in was transformed. At the time (early 2016) these Lenz decoders could be bought for around £12.50 from a couple of big German box-shifters so I started a complete replacement program. I was astonished that all my old TCS, Bachmann and Hornby decoders sold on Ebay for a lot more than £12.50. Latterly I've used some Zimo MX600R and MX638 decoders which also perform superbly. 1 Link to post Share on other sites More sharing options...
BromsMods Posted November 24, 2020 Share Posted November 24, 2020 12 hours ago, RFS said: They did exactly the same so it seems the same poor BackEMF algorithms are still being used. Some TCS decoders exhibit the same trait. Not any more........ 1 Link to post Share on other sites More sharing options...
philg Posted November 24, 2020 Author Share Posted November 24, 2020 10 minutes ago, BromsMods said: Not any more........ Indeed. The DP5 I’m using now is so much better 1 Link to post Share on other sites More sharing options...
RMweb Gold RFS Posted November 24, 2020 RMweb Gold Share Posted November 24, 2020 2 hours ago, BromsMods said: Not any more........ OK - was referring to some older decoders. I had DP2X-UK decoders which exhibited the same characteristic but I accept it's now been fixed in later versions. I've edited my original post to add the word "older". Link to post Share on other sites More sharing options...
tender Posted November 24, 2020 Share Posted November 24, 2020 I found the old DCC concepts and the older TCS decoders were OK until you changed the speed settings from their default values. Not tried any of the newer versions, once bitten etc. 1 Link to post Share on other sites More sharing options...
DCCconcepts Posted November 24, 2020 Share Posted November 24, 2020 17 hours ago, philg said: tbh this is an old ZEN so maybe things have got better Hi Phil, What value is in CV7 of the errant decoder? Best Regards, The DCCconcepts Team Link to post Share on other sites More sharing options...
philg Posted November 24, 2020 Author Share Posted November 24, 2020 1 hour ago, DCCconcepts said: Hi Phil, What value is in CV7 of the errant decoder? Best Regards, The DCCconcepts Team It's a direct 8-pin plug decoder (no harness) and in a blue shrink wrap. I suspect it's a tad old, but I only just got around to using it CV7 is 034 (decimal) Link to post Share on other sites More sharing options...
DCCconcepts Posted November 25, 2020 Share Posted November 25, 2020 17 hours ago, philg said: It's a direct 8-pin plug decoder (no harness) and in a blue shrink wrap. I suspect it's a tad old, but I only just got around to using it CV7 is 034 (decimal) Hi Phil, Thank you for the information. CV7=34 is a relatively old decoder - we have upgraded the software since then. We have sent you a PM. Best Regards, The DCCconcepts Team Link to post Share on other sites More sharing options...
philg Posted November 25, 2020 Author Share Posted November 25, 2020 56 minutes ago, DCCconcepts said: Hi Phil, Thank you for the information. CV7=34 is a relatively old decoder - we have upgraded the software since then. We have sent you a PM. Best Regards, The DCCconcepts Team I guessed it’d been lying around for some time. A few years ago real life intruded on my modelling hours and I’m only just getting back to trains 1 Link to post Share on other sites More sharing options...
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