needing a little advice on TCS T4X decoder
#1
Hi all, I've got a Athearn RTR SW1500 that I'm struggling to set up. I won it on e-bay and it came with an NCE decoder build in. This decoder was very basic however (it was an N scale decoder to boot), and I couldn't coax any low speed performance out of it. In fact, I needed to increase the throttle when it would suddenly start to move, but not good enough for switching. I still had a TCS T4X decoder sitting around, which I had used previously in another loco before that one was converted to a sound equiped decoder.

So I swapped the decoder and set about tuning it. Low and behold,thanks to BEMF I can control it now on really slow speeds, but the problem is now if I accellerate. The loco speeds up , and then while the throttle increases , the loco slows down again, and somewhat mid way throttle comes to a stop. I think this is due to the BEMF changeover point, where BEMF is gradually reduced. It cannot be tuned as TCS BEMF feature is fully automatic.

I then decided to try it without it, and experimented with the dithering function instead (various 'kick' frequency and amplitude combinations attempted) with similar results.

Has anyone seen this kind of behaviour before, and what can be done to solve it?



Thanks very much for your tips and insights.

Koos
Be sure to visit my model railroad blog at <!-- m --><a class="postlink" href="http://www.namrr.blogspot.com">http://www.namrr.blogspot.com</a><!-- m -->
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#2
Koos;

I'm having the same problem you're experiencing with a TCS decoder I put in an Athearn CF-7. Forget the decoder model, but it acts just as you describe. After trying all sorts of settings, it will start off nice and slow about 1/2 scale mph (using 28 speed steps), but as you increase the speed (around speed step 4 or 5), the loco will stop and then only move again when you advance to about speed step 7 or 8. Behaves the same way if I use 128 speed steps. I think I've tried the same things you have with no improvement in performance.

I'm hoping that someone on here that's really good with DCC can give us both an answer as to what to do!
Ed
"Friends don't let friends build Timesavers"
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#3
Well I have been in touch with TCS tech support, to see if they had an answer:
This is what they wrote: "BEMF is on all the time as a default. what you are seeing is a minor overshooting of the BEMF and can be compensated for with CV3 and CV4 Acceleration and Deceleration.
For an explanation of why this happens , it is the nature of the beast connected to the individual locomotive.
It can be just a variation of a motor or gearing or a combination"

In other words, a pretty vague reply. I do have some degree of momentum (acceleration and Deceleration) programmed in.
Ed, I'm not sure if you have the same? I guess we could try to increase these values first, or go the other way and remove it completely. I'm currently away on a trip though and won't be able to try this out for at least a week or more, so if you want to go ahead and try it first, and see where that leaves you with your CF7?

I look forward to what you find, and if you don't mind, share your CV settings here?

Cheers, Koos
Be sure to visit my model railroad blog at <!-- m --><a class="postlink" href="http://www.namrr.blogspot.com">http://www.namrr.blogspot.com</a><!-- m -->
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