firs try at DCC, not so hot


tankist

tankist

Active Member
the system i have is MRC prodigy express.
i have bachmann spectrum SD45 with factory DCC installed. it is limited to 28 speed steps, has only light , and dim functions but it works. reprogrammed it to match the 4 digit road number and all is fine. i don't like that it needs to be at speed 10 to start mooving (anything below and its crawling). played with CV and TV values, no change whatsoever. it almost seems like the decoder did not take values but thats not the case since when i programmed ACC and Dec values i definitely felt effect. i also wanted to enable the back EMF (if any on that decoder) but for the life of me i can't find the values table anywhere...

tried installing what i think is basic decoder from MRC. the only marking on the black wrapper is "made in china" but looks just like that one:
http://www.modelrec.com/search/product-view.asp?ID=7736
opened DCC quick plug athearn CF7 and apparently i will need an adapter (don't feel like cutting the harness out) - it asks for 8 in a row plastic connector while the decoder i have is 2x4 pin grid. oh well i thought and moved to Spectrum dash-8. that one has the 2x4 grid. plugged the decoder inn. all went well, loco responded to input, the only issue was no lights. tried to program address on main line, and it didn't take it. just kept responding to address 2.
so i put it onto program track and tried to give it 4 digit adress to match road number. put it back on the line, it no longer responded to address 2, neither to new adress, so i thought the decoder might not support those (which it should). back on program track i sent adress #4. and now the weirdest thing - it does respond but now it just pulsating (3 times a second). the higher the throttle position the stronger it jerks... is it shot?

any idea?
somehow i think i'll need to by proper digitrax decoder (for the athearns for sure)
 
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Anton, I think you probably used a combination of CV values that screwed up the built-in speed table. Reset the decoder by using CV8=8. That should reset to the standard address of 3, or 2, with some MDC decoders. If it runs correctly then, you know that was the problem. It sounds like you might have an older decoder that only accepts two digit addresses. Try programming the last two of the engine number and see if that takes. The light issue may be that you just have to press F0 (zero) on your controller to get the lights to come on. Some MDC and Bachmann decoders do this by default.

Bachmann decoders that ship with the Spectrum line only have a 28 step speed table and no back EMF. They are about as basic as you can get. Most of us that need to do consisting or speed matching pitch them and get a proper decoder. I personally like NCE decoders but Digitrax or TCS also make good decoders. MRC decoders are pure junk. Poor quality control, lousy documentation, and they do things like loose the engine address every time you power down. They are also as expensive or more expensive than any of the good decoders I listed. I'd give it one more try with the two digit address. If that doesn't work, consider it a lessson and get a good decoder.
 
CV8=8, thank you i'll try it. as far as light, i did try the F10 . i tried all the F's for that matter but it is not a concern at the moment, after things are rolling again i'll tap the pins directy with LED. i am planning on getting better decoders anyways but for now still like to use what i can use.

anyone happen to come across CV table for the Spectrum factory decoder (i searched for half hour or so )? upsetting a bit that they couldn't have just put that piece of paper in the box instead of advertisement flyer...
 
Anton I think your just getting fimmilar with DCC you sound like I did with my first decoder instalation. After a while you will learn the baisic and have a better understanding. I dont have any MRC decoders but just about all decoders have a V start setting and V max. some high end decoders dont use the the V start and V max CVs that MRC uses in the default program screen. you need to find their chart that shows how to adjust them. and go from there. I have the MRC advanced 2 and I love it. by far one of the simplest I have use for a small/med sized home layout. one trick if you dident know.... if a loco shorts the layout but continues running the screen may say "savd" just unplug the hand held throttle, wait 3 sec and then plug back in. for the first 3 months I would turn power off and back on LOL
 
Trent, thanks.
different CV adresses then set by, that makes perfect sence. more reasons to have CV table... as far "Savd" error yeah i got it couple of times and figured out throttle unplugging. i wish there was an easier way to reset a cab, because that usually acompanied by some sort of derailment and there is a need to stop the train now. i think i'll just make some sort of "emergency disconnect" between the controller/booster and rails. havent looked much into it yet however.
 
apreciate it a lot. you kind off put me to shame. i started byt combing bachmann website. somehow i went just right past that "1 amp decoder" PDF... took a look just now and here it is obviously.

thanks!
 
thats what message boards are for.... helping and sharing info... i did not look at it closely but I did not see a speed table? you may not have a max speed cv to adjust?
 
The Bachmann decoders do support 128 speed steps, and to reset an MRC decoder, you program CV125 to 1, not CV8 to 8(programming CV8 to 8 is reset for Digitrax decoders).
 
allrighty, troubleshoot some more today.
started by trying to set CV125 with value 1 - no change.
made sure for good contact (really presed that plug in). on programm track sent adress 2. no change, kept jerking.
on the program track again sent adress 2, CV-1, ACC-1, DEC-1, TV-32 (basically default values). and it started moving again. lights do work as they should. tried to give new adress again on the main, it ignored it and kept responding to address 2. programmed it to adress 3 on programm track, stopped responding to addr 2 but also wouldn't respond to 3. reprogrammed to 2, back to where i stated - all working fine.
actualy not fine for some particular reason when i pres on red stop it just takes off - goes full speed forward regardeless if it was going fwd or reverse at that point...

tried another decoder, does exactly the same thing


i have this feeling that the decoders are either not MRC, or just some very very old model and i'm pushing wrong values... pulled up the manual of discontinued 1650 and even though the pic looks similar i don't think it is it as the manual mentioned additiona contactors underneath wrapper that ones i'm working with simply don't have. anyone can help identify?
i'm not particularly set on using them and could chalk up the 40$ i paid for the 4 pack to learning curve but still would be nice if they can be programmed properly


EDIT:
on a plus side i took time today to do proper wiring to the mainline (soldered a lead from underneath the table), attached the command station/booster underneath a tablel and established proper programming track.
plugged in old digitrax DH121 i had into that CF7 loco and all is good, long adresses, BEMF compensation is awesome! it will only program on program track though. the only things not to like is the decoder getting hot and at low speeds there is quite anoying noise... i guess the advertised "ultra quitness" of new decoders takes care of that.
 
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I have had a engine just take off but only when the engine was still acceling to the speed I wanted and it had shorted through a switch. My soundtraxx decoders do this. I think its called the stay alive capasitor? when it shorts it remembers the speed it was to accel too/hold but does not recall where it was in the accel range. I think some decoders do this so when you have 3 locos pulling and one goes dead. it will quickly recover to the speed that the other 2 were at. If you want to try a cheap decoder look at a base line Digitraxx. the digitraxx will have some more options than the MRC. learn with the cheep decoders then move to the sound. Sound is fun once you learn the basics!
 
Thanks, Robert, I always forget that MRC has that strange CV125 reset. The only standard Bachmann decoder I still have (which is really a Lenz) is in my 70 tonner, and it has only 28 speed steps, as confirmed by Decoder Pro. It looks like the later version added 128 speed steps, which is a good thing.

Anton, if you put your locomotive on the programming track and set it read CV8, it should come up with a number that corresponds to the decoder manufacturer. I think the NMRA web site has a listing of the number code for each company. Reading CV7 should then give you the version number. I'd do that before I went any further, since entering MRC CV values in a non-MRC decoder will get you into nothing but trouble.

Runaways on DCC arer almost always caused by having the decoder in dual mode, so the engine will run on analog or DCC power. Once you find out for sure what kind of decoder you have, there's a CV value you can set that makes the engine DCC only and usually ends the runaway problem. Since you're not using sound, it's almost always better to do your changes on the programming track. Most controllers will not read back values when programming on the main and reading back values once you've set them at least confirms you did what you think you did. :)
 
Jim, i don't think i can read values with prodigy express. only the advance model offers that. i am thinking about picking up the advnce cab but it says incomaptible with express, which really makes me question if it is realy incompatible or was specificaly made so to sell the entire advance system. i mean if i'll plug advance cab into the express command station will it really not work? if so, sounds dumb...
i guess i will be looking for modelers with proper DCC setup near me.

the dual mode makes sense.

the person i got decoders from was also selling old MRC command 2000, so i'd guess they are that old.
 
tankist said:
...i am thinking about picking up the advnce cab but it says incomaptible with express, which really makes me question if it is realy incompatible or was specificaly made so to sell the entire advance system. i mean if i'll plug advance cab into the express command station will it really not work...
Click to expand...

Where does it say incompatible with express? The Prodigy Express manual clearly states "If you add a Prodigy Advance Cab to your Prodigy Express, it will automatically upgrade to Prodigy Advance DCC System." It also list in the features "Read Loco on Program Track with Prodigy Advance Cab."
 
NVM,i think i seen this comment on some retailer website. MRC says "incompatible with prodigy" which they probably refer to their obsolete system.

<thinking aloud>
~ 80$... do i really need 3 cabs...
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What kind of engine is it going in? The DH121 is a very basic decoder with limited lighting support and no Back EMF. If it's going in a BB Athearn, it will be fine. If it's a newer engine, I would spend the money and get a DH163P, assuming you have a nine pin DCC plug already on board. It's not very expensive and will do a lot better job with a nice locomotive.
 
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