I bought a used P2K FA2 off Ebay that is equipped with an MRC AD350 decoder. As soon as I put it on the track it starts running at a high rate of speed. I have no control of it whatsoever. My DCC is a Digitrax Zephyr. Any suggestions as to why this is happening? I’m just starting out and have one other DCC loco that works fine. DC locos also work fine. The seller said he tested the loco before listing it with an MRC Prodigy on address 6.
Thanks
Todd
Just to be sure, select address 6 before settign the loco on the track and make sure the throttle is on stop. If it still takes off - I’d say the decoder is bad. Given that it’s an MRC, it’s highly likely.
Also select address 00 and set it to stop too. The MRC decoder may see the zero stretching as DC power and act appropriately.
–Randy
There could be two causes: 1. It’s an MRC decoder. They are known to be terribly unreliable. 2. The decoder has been improperly installed and is shorted out.
With e-Bay, you get what you pay for. The seller got rid of his problem locomotive – now it’s your problem.
Join this MRC group. This group specializes in MRC DCC. I belong to the group but I do not used MRC products anymore.
http://groups.yahoo.com/group/MRC-DCC/
Rich
Put it on the programming track and check CV29. Analog conversion mode needs turned off. Set CV29 to 34 or 35.
Agree. I had a digitrax decoder do the same thing. Turning DC mode off fixed it.
I changed the loco address from 6 to 7 and it started to work properly. Don’t know why that would fix it but I’m not complaining! Maybe the MRC decoder needed a good Digitrax kick in the butt!
Todd
Check what the Digitrax throttle set CV29 to. The standard value for a DT400 is 38, which leaves analog conversion mode enabled. 34 is the same thing except analog conversion mode is disabled. I don’t know what the Zephyr default value is when you set a 4 digit address.
I would listen to the cv 29 suggestions. The symptom of an engine taking off might seem to disappear but it will come back. You can run fine for weeks and all of a sudden it will run at max speed until hitting something if not grabbed in time.
Personally, I would remove the decoder and scrutinize the electrics with a Multi meter. I would then spend a few bucks and get something of quality under the hood.
David B
Same thing, 38. I have to say, I never had any just take off when I turned on the power, even with analog conversion on, with NCE, Digitrax, and TCS decoders. Something is making it ‘see’ DC, or like I mentioned, address 6 was set to full throttle and cleared without being set back to speed 0. I do generally tuen off analog conversion, as the only places I can thing of that I’d ever run my locos are places that have some brand of DCC system, but I didn;t always do it that way.
–Randy
I’ve been running DCC for 10 years now, and I’ve seen the ol’ CV29 analog mode “take off” happen many, many times both on my home layout and my rather large club layout.
Every DCC user should turn off analog mode when not running analog.
It’s been explained to me that when there is a series of short circuits or power ups, the decoder can be fooled into thinking it’s seeing straight DC (after all, DCC is an AC square wave form, and the initial burst of DCC is, essentially, DC). When analog mode is turned on, if the decoder senses DC voltage, it will take what ever power is in the rails and send it to the motor. Of course, with DCC, that’s full power. So the engine suddenly accelerates like a top fuel dragster and you’re bound for a collision with something (track bumper, another train, the floor, etc.).
Paul A. Cutler III
Weather Or No Go New Haven
I’ve had it happen a couple of time with dirty track where I would push the locomotive over the dirty spot and then it would take off. Of course I cleaned the track but it took a couple of these for me to figure out what was happening. I agree, it will come back if this is not disabled… From what I remember (since it’s now been a number of years since it occured) it happened across multiple decoder vendors and it seems like the first generation QSI sound decoders were the most sensitive to this.
Well, it happened again tonight. I checked CV29 and it is set at 2. What should I change it to to disable?
A value of 2 has it turned off. A 2 means 28/128 step speed table, normal direction of travel, analog conversion mode off and 2 digit addressing. This means something else is wrong. I’d seriously consider another non-MRC decoder.
I think the decoder finally bit the dust. I get no response at all now. Nothing, Nadda…
Just as well as the motor really sounded whiny with this decoder and I think I’d like to go with a sound decoder. Any recommendations?
It’s surprising to me that MRC makes such a substandard decoder. Their other products seem to be pretty good.
Todd
Hi Todd,
I had a new Bachmann 45 tonner with a MRC decoder in it that did the same things as yours. I eventually got it replaced with a new loco. If the decoder has now failed fully, don’t put another MRC decoder in it. Get a decent decoder to replace the MRC one. I haven’t got a sound decoder yet but I hear (pun intended) that the TCS ones are good.
cheers
Digitrax, NCE and TCS all make very solid decoders. Just find the one that you like and is the easiest to be a drop in replacement.