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.
You'll get some help before long.
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.
Do yourself a favor and replace it with a cheap TCS decoder. Early MRC decoders are nothing but misery.To quote my late grandfather, "not worth the powder to blow them to Hell."
Disclaimer: This post may contain humor, sarcasm, and/or flatulence.
Michael Mornard
Bringing the North Woods to South Dakota!
wjstix I assume it's an MRC decoder given the title, but 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. 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.
I assume it's an MRC decoder given the title, but 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. 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).
There is no model number on the decoder. I meant to mention that in the OP and just forgot.
I've tried entering a two digit address but even that won't take.
My Lenz system doesn't display the current CV values.
Try a resistor, even temporarily placed. I think 700 ohms ought to be enough.
MrMe 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.
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.
John,
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.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
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.
https://www.internetmodeler.com/2001/january/railroad/mrc_f7a_review.htm
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.
Shane
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
Lastspikemike CV29 determines motor direction assuming the wiring is conventional. You deduct 1 from whatever CV 29 currently reads to set reverse direction.
CV29 determines motor direction assuming the wiring is conventional. You deduct 1 from whatever CV 29 currently reads to set reverse direction.
Alton Junction
wjstix 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. https://www.internetmodeler.com/2001/january/railroad/mrc_f7a_review.htm
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.
John, right click on the desired photo in Imgur, then click on Copy Image. Then, simply click Paste to place the photo in your post.
Rich
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.
Pete.
Lastspikemike Not if it's already running in reverse.
Not if it's already running in reverse.
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.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
LastspikemikeThe 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.
Is this picture you referred to of one of your locomotives?
If not, why not share example pictures of your own? That would be welcome and helpful.
-Kevin
Living the dream.
SeeYou190 Lastspikemike 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. Is this picture you referred to of one of your locomotives? If not, why not share example pictures of your own? That would be welcome and helpful. -Kevin
Lastspikemike 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.
Yes that looks pretty much how mine looks without the decoder. I assumed that green board indicating where the various colored wires would attach was an indication that mine was a factory installed decoder but now I'm guessing they put that green board there to make it easy to install a decoder into a DC loco.
Lastspikemike 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.
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.
Isn't the loco address stored in CVs. Do you know which CVs would be used for the address.
UPDATE: I found this online manual for an MRC decoder. As I suspected, the long address requires a two byte address. In this case it's CVs 17 and 18.
1661_4-FUNCTION_DECODER.pdf (gaugemasterretail.com)
The loco's road number is 1830. Having been a mainframe programmer for much of my life, I know how to convert decimal to binary but I'm not sure what values to plug into the two CVs to get the appropriate address. Do I enter 30 in the lower byte? If so how do I get 18 in the upper byte given that the range for that is only 192-231? Or is it more complicated than that?
John-NYBW Isn't the loco address stored in CVs. Do you know which CVs would be used for the address.
Long addresses are stores in CV17 and CV18. But that gets complicated.
You cannot simply split the four digit long address in 2 halves and input these into CVs 17 and 18. A conversion from decimal numbers to hexadecimal numbers is required. Once the hexadecimal conversion for the 4 digit long address is performed, this number is then split in half and then each half is input into CV17 and CV18 respectively.
I am most familiar with NCE DCC systems in which you input the actual 4 digit long address with the cab, and the system does the hexadecimal conversion.
John-NYBWThe loco's road number is 1830. Having been a mainframe programmer for much of my life, I know how to convert decimal to binary but I'm not sure what values to plug into the two CVs to get the appropriate address. Do I enter 30 in the lower byte? If so how do I get 18 in the upper byte given that the range for that is only 192-231? Or is it more complicated than that?
Below is a handy CV converter for CVs 17 & 18 from the Digitrax website. It also includes CV 29 and several other helpful tables:
https://www.digitrax.com/support/cv/calculators/
For a cab address of "1830", CV17=199 & CV18=38.
richhotrain John-NYBW Isn't the loco address stored in CVs. Do you know which CVs would be used for the address. CV1 is the Primary Address, sometimes referred to as the "short address". Long addresses are stores in CV17 and CV18. But that gets complicated. You cannot simply split the four digit long address in 2 halves and input these into CVs 17 and 18. A conversion from decimal numbers to hexadecimal numbers is required. Once the hexadecimal conversion for the 4 digit long address is performed, this number is then split in half and then each half is input into CV17 and CV18 respectively. I am most familiar with NCE DCC systems in which you input the actual 4 digit long address with the cab, and the system does the hexadecimal conversion. Rich
CV1 is the Primary Address, sometimes referred to as the "short address".
It looks like you posted your reply as I was posting my update so you have answered my question. My loco roadnumber is 1830. If I did my hexadecimal conversion correctly, that's 726 in hex. So do I plug 26 into CV17 and 199 into CV18? It looks to me that CV18 is using a displacement of 192. Not sure where that comes from.
long Address - 1830
CV17=199
CV18=38
John-NYBWIt looks like you posted your reply as I was posting my update so you have answered my question. My loco roadnumber is 1830. If I did my hexadecimal conversion correctly, that's 726 in hex. So do I plug 26 into CV17 and 199 into CV18? It looks to me that CV18 is using a displacement of 192. Not sure where that comes from.
The 192 comes from the DCC command format. When sent as a command to the primary address, the first byte of the packet is the address byte, 0 - 127 (0 is the braodcast address and only used in special circumstances). If the first byte is greater than 127, then that signals to the decoder that it is an extended packet. There are some special instructions in there from 128 - 192, so a control command to the extended address has to be 192 or above; therefore, to send the upper byte of the extended address you have to add 192 to it.
It wasn't really necessary to have it programmed into the decoder that way, the decoder could have added the 192 before doing the comparison, but the processors in the early decoders were etremely limited and by programming the address with the 192 added to the upper byte made it much easier on the decoder to do the comparison.
tstage John-NYBW The loco's road number is 1830. Having been a mainframe programmer for much of my life, I know how to convert decimal to binary but I'm not sure what values to plug into the two CVs to get the appropriate address. Do I enter 30 in the lower byte? If so how do I get 18 in the upper byte given that the range for that is only 192-231? Or is it more complicated than that? John, Below is a handy CV converter for CVs 17 & 18 from the Digitrax website. It also includes CV 29 and several other helpful tables: https://www.digitrax.com/support/cv/calculators/ For a cab address of "1830", CV17=199 & CV18=38. Tom
John-NYBW The loco's road number is 1830. Having been a mainframe programmer for much of my life, I know how to convert decimal to binary but I'm not sure what values to plug into the two CVs to get the appropriate address. Do I enter 30 in the lower byte? If so how do I get 18 in the upper byte given that the range for that is only 192-231? Or is it more complicated than that?
OK, I think I understand now. The upper byte (CV17) uses the displacement of 192 + 7 to get 199. The lower byte (CV18) uses 38 which is the decimal value of hex 26. A four digit loco address is first converted to a hexadecimal number. The last two digits of that hexadecimal number are then converted back to decimal, in this case hex 26 to decimal 38 which is plugged into CV18. the high order digit(s) of the hex number are then added to 192, in this case 7, for a total of 199 which is plugged into CV17.
I'm still trying to figure out why the displacement of 192 but if I rack my brain long enough I might figure it out.
If you do get the extended address programmed, you would also need to program CV29 to activate it. CV29 also controls 14/28 speed steps and normal direction of travel. The best thing to do for it is use one of the CV29 calculator like the Digitrax one on the page linked to above.
I retired from mainframe programming in 2001 and I think this is the first time since I've had to deal with binary and hexadecimal math. When I first got into the business in the 1970s, we had to deal with base registers and hexadecimal displacements in order to debug a program but by they time I retired that had become a lost art. I don't think I even remembered how to do it at the time of my retirement. Sometimes we had to do binary conversions if we needed to deal with individual bits.
richhotrain Lastspikemike CV29 determines motor direction assuming the wiring is conventional. You deduct 1 from whatever CV 29 currently reads to set reverse direction. 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.
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.
You're both assuming something, either that the wiring is correct and reverse is programmed into CV29, or CV29 is correct and the wiring is reversed. We all know what happens when we assume, don't we.
The correct way to reverse the direction of a loco using CV29 is to read the value and add one if it is even and subtract one if it is odd. If CV29 is even and you subtract one, or if it is odd and you add one, you will be changing other settings as well.
LastspikemikeOf course if the wiring is reversed that's the other possible reason. North American decoders accept two digit addresses up to 99.
Digitrax, NCE, and TCS all accept primary addresses from 1 - 127, in fact, I don't know of any cuurent production decoders that don't.
Incidentally, I hate the all to common use (even by manufacturers) of "2-digit" and "4-digit", and "long" and "short" addresses because I believe they just add to the confusion. The proper terms are primary address,which can be 1-127, and extended address, which can actually be 0-16,239.