Truck If you put a quality decoder in an over priced peice of crap locomotive...
If you put a quality decoder in an over priced peice of crap locomotive...
Not sure why you would say the Cab Forward is a piece of crap locomotive, according to everything I have read it appears to be very nice.
There's never been a problem with either of my Cabforwards;they both ran great with impressive slow speed creeping on DC.And the decoders themselves are great too,they needed fine tuning and the problem was that I didn't know anything about BEMF.Had I known,this post wouldn't exist.
If you put a quality decoder in an over priced peice of crap locomotive, you will have crapy results.
I run N & HO scale on the same layout with no issues. The only locomotive I ever had that recomended 12vlts to track power was an Athearn N scale Challenger with MRC sound from factory. But as soon as that decoder fried I put the Soundtrax replacement in it.
I run a lot of TCS decoders in my N scale and HO scale loco's. And they all run fine. Track voltage is at 14 volts. I did buy the MRC track voltage reducer for the Challenger with the MRC in it to drop it down to 12 volts and the decoder still fried. Took out the reducer and all is good.
Iwas going to purchase one of those IM cab forwards but after what I have witness with then I will put my money somewhere else.
Truck.
CV2 was set to 0 throughout the above example.
What I have found with adjusting Dither is to set CV2 to 0 first. Then adjust CV57 on SS1 till the motor just starts to go. Then adjust CV56 until it is smooth. Then I enable BEMF in CV61 and adjust CV2 last if needed at all. I have CV10 set at 20 or 30 depending on the engine and I do not get the speed change when BEMF shuts off. I find that having too much starting voltage will affect Dither settings. On my switch engines I leave BEMF enabled all the time.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
rrinker That's kind of odd since if BEMF is off there is no other choice but to use the dither settings. --Randy
That's kind of odd since if BEMF is off there is no other choice but to use the dither settings.
--Randy
That is what I would expect, but it is not the case. If bemf is "enabled", but turned off, it ignores the dither settings(acts as if one of the settings is 0, which would disable dither). For example, with bemf disabled(CV61=0) and dither disabled (CV57=0), the loco will not move until about 20% throttle. I can set dither so the loco will just creep at throttle setting 1(CV57=75, CV56=default=3). Enable bemf, set so that I can turn it off with a function key(CV61=3). If I have F6 off, allowing bemf, the loco moves at speed step 1 and accelerates as I increase the throttle setting. If I turn F6 on, which turns bemf off, then the loco will not move until around 20%, just like it did with CV57=0, even it is still set to 75. If the loco is moving with F6 off(bemf on) and I turn F6 on(bemf off), it will suddenly slow down. If I am below 20% throttle when I do this, it will stop. Likewise, if for example, I set bemf to turn off at speed step 15, the loco will move at step 1, and accelerate as I increase the throttle, until I get to speed step 15. It will then stop and not move again until I get to 20%.
You both were right,BEMF was the glitch.Since I don't feel I'll need it I turned it off but lost the creeping qualities the loco had before.I've had to tinker with Dither numbers to regain them.It's a little short of perfection but still quite nice.I didn't feel much change with CV56 so left it at 03 but had to set CV57 at 45.Still needs a little tinkering but I know I'm in the right direction.Thanks gentlemen.
Modeling the Reading Railroad in the 1950's
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rrinker ... Turn BEMF off, adjust dither, then turn the BEMF back on and there should no longer be any sudden speed changes...
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Turn BEMF off, adjust dither, then turn the BEMF back on and there should no longer be any sudden speed changes...
I tried that, and it did not make any difference. In fact, when I have BEMF enabled, if I have it turn off by speed step or by a function key, the decoder does not revert to using the dither settings.
Hmm, I'm in HO so maybe there is a difference, btut I don't notice a speed drop when moving from the speed step with BEMF to the speed step where it cuts off with my TCS decoders. I prefer to have BEMF on only at slow speeds so I can run smoothly at low speeds while switching, but not have cruise control on the main - although at present the only grades I have are because my room isn't level. When the BEMF is turned off on the newer TCS decoders, you're back to using their dither control, which can be tuned quite a bit. I have some older TCS decoders from before BEMF and those locos will creep on step 1 almost as good as the same loco with a newer BEMF version decoder. This tech note explains the BEMF turn off setting and also explains how to tune the dither settings: http://www.tcsdcc.com/public_html/Customer_Content/Technical_Info/Tech_Manuals/BEMF.pdf
Turn BEMF off, adjust dither, then turn the BEMF back on and there should no longer be any sudden speed changes. It was the sudden speed changes that made me stop using Digitrax decoders - they gathered the 'error' from a non power of 2 divide (digital computers can't return exact results when working with numbers that are not evenly divisible by 2 - math routines can compensate for this but only out to the accuracy of said routine - 16 bit, 32 bit, etc. And the PIC chips uses in most decoders are not designed to be calculating machines) into a coupel of speed steps so while from say step 5 to 6 ther is a small increment of speed, at a coupel of steps along the scale there are much larger jumps in speed. Other decoders seem to spread this error out over more or all steps, so the difference in speed between each step is equal (unless you adjust the speed tables or set up a 3 step speed table to make the response non-linear). ANyway, enough technical mumbo-jumbo, I'm quite happy with TCS so far. Not sure about these new ones with keep alive, might be useful for the club where the connector tracks between modules always seem to have pwoer issues, but my home layout I never have a problem, even though I never clean my track.
The only thing you can do to "tweak" the Bemf compensation operation on TCS decoders is have it turn off at a certain speed step(which I find unsatisfactory because there is a sudden drop in speed at that point) or have a function turn it on and off. There is nothing, at least that I have seen, that you can do to actually adjust it's operation.
I agree with Randy that it was probably the bemf that was limiting the top speed of the loco. The motor in this loco appears to be somewhat different than most N scale motors(it seems to produce relatively high bemf voltages at lower speeds than most). I have heard of others with the same problem(low top end speed) using other brand decoders, and turning off bemf compensation fixed the problem. When using bemf compensation, the decoder compares the bemf voltage to a reference voltage to try to maintain a constant bemf voltage for a given speed step. Once the bemf voltage reaches the expected maximum, the decoder will stop increasing the output, even if you continue to increase the throttle position. By increasing the track voltage, you probably increased the reference voltage that the decoder compares the bemf voltage to, allowing the decoder to increase the output beyond what it did previously.
Generally to control the peak voltage to the motor. Digitrax is the only one to even have a 'scale' switch, most of the others put out a set track voltage and that's it, sometimes adjustable with an internal knob, sometimes adjustable with a ccommand station configuration setting. A Zephyr doesn;t have an adjustment, and the original (DCS50) with the supplied power supply put about 12.5 volts to the track. My HO locos ran plenty fast. I do have my DB150 set on the HO setting, but I had to adjust a few of my older locos that were originally configured on the Zephyr as far as start, mid, and max since the slightly higher voltage altered those settings.
Probably what sucked up the top end was the BEMF in the TCS decoder. I've been using nothign but TCS decoders for the past couple of years, other than sound locos, and all mine seem to run plenty fast at full throttle, far faster than I'd normally run them anyway. I have an AB set of FTs, once with a Tsunami and I put a TCS T1 in the other, and they run well together with almost no adjustment, even at full throttle, the Tsunami doesn't outdistance the TCS as might be expected if there was a serious fault in the TCS BEMF. That's why I use the TCS decoders, their BEMF works very well. They call it self-adjusting, and it seems to at least do SOMETHING - when I put a new loco on the track it runs rough for a little bit, especially at slow speed, but after a lap or two around the layout it really smooths out. It seems to stay that way even if not un for months, so if there is any internal automatic adjustment occurring, it gets written to the decoder's memory somewhere.
Even though it is sold as self adjusting, there are some CVs that cna tweak the operation. On the TCS web site they have some additional manuals on things liek BEMF and lighting effects. The simple quick start that comes with the decoders barely scratches the surface - there are all sorts of thing you cna do with the lighting effects that aren't even mentioned in the basic instructions. Unfortunately, or perhaps fortunately for me, my era/prototype doesn't need any effects, just basic on/off headlights, no beacons, no ditch lights, no Mars lights. Doesn't mean I haven't played around a bit, making the headlight act like all sorts of flashers and blinkers just to try out the different options.
Come to think of it,if voltage isn't an issue,what's the purpose of the different voltage settings in front of a DCS100 command station?
Randy,I get your point.However,raising the voltage a bit did correct my problem.My interpretation of your saying is that there can be only two factors left,either a CV that's reducing voltage to the motor or these engines are power hungry.TCS say on their website that a drop of about a volt between track and decoder outlets is normal,so I agree with you that the remaining twelve volts should be OK for N scale.That is assuming that HO runs on 13 volts or more on a DCS100's HO setting.
I purchased these decoders because they were the ones TCS recommend for this particular application.I have other TCS decoders and never had problems of any type.I have two identical loco/decoder pairs and both behaved exactly the same both before and after the voltage change.So if there's a better solution,I don't know it.I did as TCS say,they even have pictures of this setup on their website.
By the way,both locos ran great on DC if that means something.I don't mind running my locos on HO settings,as long as it doesn't harm my other N scale decoders.
That shouldn;t be an issue at all, although different track voltage will certainly change the top speed. They do have several "N scale" decoders, most of which are specific board replacements. The MC2 can be had with a harness that plugs in to the 8 pin socket in the loco. The idea of HO, N or Z scale decoders is mostly one of physical size and current capacity. There is no technical reason or differeing design as to why an "HO" decoder that physically fits wouldn't work in an N scale loco. In fact the opposite is done quite often, for small low poer HO locos that don't have the room for a decoder, an N or Z scale decoder is used.
I recently purchased two Intermountain N scale AC12 Cabforward that I also bought two TCS DP2X decoders for.The installation was a breeze (8 pin connector) but when the engines were tested,they behaved poorly.They both were very slow and maxed out at about 50% throttle on a DT400.
Tinkering for a couple days with the CVs gave no satisfying results.About to quit,I went on TCS's website to check if these were the recommended decoders for these locos...they are.But I also learned an important point...they are HO decoders...and thought that may be it was the problem.It was.
When I flicked my DCS100's select switch to HO,the locos came to life and ran very nicely.Being designed for HO,these decoders don't get enough track voltage to perform right on N scale settings.
I tried telling TCS about this,but my Hotmail doesn't speak to their Outlook...may be someone could let them know,so that they could have a service note on this,or better still,offer an N scale DP2X...