I picked up a nice looking MRC F7 at a bargain price. I believe it has a factory decoder. There are several problems with it. For starters, it won’t allow me to assign a new address to it. It operates on the factory default address of 0003 but I can’t change it. I’ve tested my programming track with other locos and have no trouble assigning loco addresses with it so that is not the problem. For some reason this one won’t allow me to assign a new address.
Another issue is that it runs in reverse. This is mainly a nuisance since I can remember it runs in reverse.
It only has 14 throttle steps. It also doesn’t seem to have any momentum programmed into it. When it hits the start up step, it takes off like a jack rabbit.
If appears to be a very basic decoder with black shrink wrapping. I believe it is from the early 2000s but I can’t be sure of the date. I think I might be able to fix some of these issues but I have no documentation to tell me which CVs to adjust.
Isn’t the loco address stored in a couple CVs and is that standard for all decoders. I believe CV3 and CV4 are standard for momentum setting. There is also a CV to dictate direction but I don’t know which one that is. I’d also like to increase the throttle steps.
Does anyone have a guess as to what the model number of this decoder is and if there is any online documentation for it. This could potentially be a decent loco if I could figure out what CVs to adjust.
I could replace the decoder but it would be a lot cheaper if I could just adjust this one.
Back when I was young in the hobby, only 15 years ago, there was a lot of salty language posted over the MRC decoders at the time. They didn’t play nice, or they didn’t often play at all, not even right out of the box. Those who had them looked to the new high-falootin’ Tsunami as a replacement.
I have never had an MRC decoder, but if I recall all their vexxed owners discussing, that one brand of decoder needed a resistor across the programming tracks to get at least the initial addressing completed. After that, I dunno.
Early MRC decoders were nototious for limited programming options, no readback, etc, so your experience with this one is typical.
Even the inexpensive “fleet” decoders from other manufacturers performed better and were easier to work with.
Many (most?) folks simply trashed the early MRC decoders and put in something (anything!) else. You may seriously want to consider that course of action.
Does it say anything on it as far as which model decoder it is? Just because it’s an MRC decoder doesn’t mean someone hasn’t put in another manufacturer’s decoder. A nice thing about getting DecoderPro set up on your computer is you can read the decoder type, and it will come up with screens showing all the options you have to program.
All early decoders were pretty basic, at one time 14 speed steps was all they had. It seems to me the MRC F7s were like in the 1990s, so that could be a very early decoder.
Also, many early decoders only used one CV for the decoder ID, so you could only do ID numbers up to I think 127(?). If the engine has a larger number, try just programming the last two (like if the locomotive is 3288, try just programming the decoder for ID 88).
Yes, CV3 and 4 control starting (3) and stopping (4) momentum. Try setting them to say 10 and see what happens, increase by 10 if you feel it needs more, etc. until it starts and stops the way you want.
If you can read CVs, read CV29 and then add 1 to whatever that number is; that should reverse direction. So if CV29 is 06, changing it to 07 should reverse the engine’s direction.
The early MRC decoders weren’t great, but I have quite a few sound MRC decoders from the last 10 years ago and for the price I think they’re very good.
I think you might be right about this. I have a basic DH126 decoder handy which would be simple enough to swap out. There is a green insulator board under the decoder which indicates which color wire goes where. I was thinking of adding this loco to an AB set to give me an ABA. I wouldn’t really need sound if I go that route although I’ve had issues speed matching a DH126 with high end sound decoders. It gets a little finnicky because the high end decoders have a different multiplier for the momentum setting.
I would toss the MRC decoder and install a better-quality decoder in your F7. I would also try to match the decoder brand of the two sound units you have for your motor-only decoder.
Just a reminder, we don’t know who made the decoder. The OP bought an old MRC engine with a decoder in it. Based on a review I found, these engines were made about 20 years ago, and were not DCC equipped (see link below). So someone, perhaps at that time, added some decoder from some manufacturer. It sounds like a very early decoder, maybe from the 1980s or 1990s. Let’s not keep repeating the ‘MRC decoders were/are rubbish’ until we find out who actually made it.
That black wrap could be after market shrink wrap. Somebody might have added it to insulate it better. My first instinct would be carefully remove it and see if I can find a name or something on the board itself. Can always put new shrink on it. or electrical tape. Wrapped decoders didnt come until later I do believe.
CV29 determines motor direction assuming the wiring is conventional. You deduct 1 from whatever CV 29 currently reads to set reverse direction.
Of course if the wiring is reversed that’s the other possible reason. North American decoders accept two digit addresses up to 99. For four digit addresses two other CV are involved each handing, in effect, two of the digits. It’s a bit more complicated than that but that’s the effect. ESU two digit addresses go up to 127.
I had thought all NA spec decoders used the same multiplier for CV3 and CV4. ESU decoders use about 1/4 the value used by NA decoders. ESU just changed that in 2021 for a NA spec series of decoders now using the NA value.
No, you add 1 to the value of CV29 to set reverse direction. If it is already running in reverse, you subtract 1 from the value of CV29 to set forward direction.
What led me to believe this was a factory decoder is that there is a green board between the decoder and the electrical contacts that indicates where each color wire should be attached. Maybe this came with the decoder but it is made to fit over the electrical contacts on this particular loco. I’m guessing the board serves to insulate as well as direct the wiring.
I’m going to take a picture of it and see if I can post it. This will be my first attemt to post a photo since I switched to imgur from Photobucket.
The clubs Lenz system read CVs on the LH100 throttles. My LH90 was a real PIA to do even the simplest of programming tasks. If you can read CV8 that will give you the decoder manufacturer code to find out who made it. CV 7 should give you the software version number if the decoder supports it.
I was quite busy in the early DCC era replacing decoders. Buzzing motors, blinking lights, melted shells from hot bulbs, limited programming options, and runaways were all too common from the first gen decoders. You would have to put dead rail sections to park the locomotive on so when the command station starts up the train wouldn’t shoot across the room with that initial jolt of DC power. Some early decoders would not let you disable DC in CV29.
I had a bunch of early MRC decoders that were wrapped in plain shiny black shrink wrap. I ended up using them for lighting control in rolling stock as the motor control was terrible.
MRC decoders should be programmed on the main according to several sources.
If it were my decoder I’d try entering a value of 6 into CV29 and see which way it runs. Deducting 1 implies you already know it’s running in reverse and you’ve read the existing value in CV29 but don’t necessarily want to change anything but the direction of the locomotive.
If you cannot read back the CV values, and you may not be able to with an old decoder, then starting with a value of 6 is a better choice. If it still runs in reverse either change the value to 7 or swap the motor wires. This decoder might not be long address capable.
The link I posted has photos of the locomotive with shell off. Which should help determine the type of decoder and whether it is wired correctiy now.
MRC uses a value of 1 in CV125 to reset the decoder at least in sound versions. Maybe older decoders had a hard reset jumper or for some reason used a different CV to reset to default.
If its running at address 3 it’s probably at factory default. The reverse direction may result from a previous owner wiring it for a consist, for example. Before consisting was programmable you set the two locomotives to the same address but wired one backwards electrically. MRC colour coded their lightboard to facilitate hard wiring the decoder. Take a look inside.