I have a 6-18221 Rio Grande SD50 w/ TMCC and Railsounds II that I had purchased new and have been using randomly over the years and has performed flawlessly, until now. Today I turned on track power and absolutely no response in any form.. no lights, no horn, no movement. I tried 3 other TMCC engines on the same track calling up their ID numbers and they work perfectly.  I tried just in case (it was somehow changed) to reprogram the SD50 with another ID (more than once) with no handshake from the SD-50 that it accepted the change.. again dead.  What I do notice is when I turned the volume up at the engine and touching any command button on the CAB-1, you can hear a low level ratchet-type clicking from the SD40s speakers that gives me the impression that the CAB-1 is communicating with the SD50.  Any suggestions other than putting it on my display shelf would be greatly appreciated? It was not involved in any collision that I can remember

Original Post

Things like this are difficult to diagnose remotely, but here are a few things to try.

1) Confirm your sound system is working OK by unplugging your TMCC Command Base and applying power to your loco in conventional mode. RailSounds should work fine -- if it doesn't, there's likely some internal short in your locomotive.

2) If RailSounds works in conventional as per the above, then the focus shifts to the LCRU1. These have a socketed microprocessor on the board, which can occasionally develop oxidation preventing it from working properly. Use a small flathead screwdriver to CAREFULLY pry up one end of the rectangular processor (it'll have a white label on it), and then do the same thing on the other end to remove it. If you have any contact cleaner handy, do a quick wipe of the pins and then re-insert the chip, taking care to be certain that it's oriented in the proper direction. Apply power to your loco and see if anything has changed.


Well here is what I know ,, it does not react in conventional mode or ant sounds,, I put 10.5 volts to the engine and it draws 65milliamps and I hear a loe level 'click' thru the speakers .. I did popped the chip and spayed it with contact cleaner as well as the PC board to no avail. I will later for possibly a loose or broken connection.  More to follow 

I should have read it first ,, should read .. Well here is what I know ,, it does not react in conventional mode or any sounds,, I put 10.5 volts to the engine and it draws 65 milliamps and I hear a low level 'click' thru the speakers .. I did popped the chip and spayed it with contact cleaner as well as the PC board to no avail. I will later for possibly a loose or broken connection.  More to follow 

It's unusual that neither the movement functions (LCRU1) nor RailSounds work, as they're basically wired independently of each other.

I've attached the wiring diagram for your loco. Two things to note:

1) There's an error in the diagram -- the solid red arrow points to the location that the violet wire should be connected to. Chances are your loco is wired properly in this regard.

2) That same purple wire is the serial communications link between the LCRU1 and RS2.5. Keep reading below.

In conventional mode, the absence of communications on that serial line will cause the RS2.5 board to start-up when power is applied to the track. In TMCC mode, the LCRU1 board sends out commands to the RS2.5 board to wait until a specific command is received before it starts up. If you don't have operation of either board, there's a limited number of things that could have happened:

-- There's an internal short somewhere in the locomotive that your transformer's breaker should be catching, but isn't.

-- The LCRU1 board failed in a way that it's still communicating with the RS2.5 board, but doesn't respond to any of the TMCC commands. I don't think I've ever seen this happen with an LCRU1, but I suppose it's remotely possible.

-- Something catastrophic happened to take out both the LCRU1 and RS2.5 boards.

If you're adventurous, here's the next thing to try: disconnect that violet wire between the two boards that I've highlighted on the wiring diagram, put the loco back on the track and apply power. If you still have the same results, then you almost assuredly have independent problems with both your LCRU1 boards and your RailSounds sound system.


18221 Wiring Diagram


Photos (1)

Thanks for a few suggestions .. here is what I know ... I too had found the wiring schematic on Lionel's website, but I do appreciate you sharing it too .. it is wired as you noted with respect to the violet wire & the red arrow. Everything seems to be secure 'wire-wise'. In regards to your suggested adventure .. I did cut the violet wire and put it on the track in conventional mode and powered it up, I do have sound (engine RPM) and have tried the horn and that works too .. what I also tried was (using a jumper) re-connecting the violet while while the Railsounds was playing and it continued to work.. I then cycled track power with the jumper still connected and NO sound on power-up. I then disconnected the jumper, re-cycled power and the sound works again.

Just for curiosity, I tried to access the engine via TMCC and the violet wire disconnected .. no such luck no matter what position I had the Prog/Run switch in .. I tried to change the units access ID .. no luck there either at this point .  

Any other thoughts ??  I really do appreciate your suggestions .. thanks

I love/hate trying to diagnose the problem, but I do enjoy the frustrating challenge, while learning at the same time .. The pre TMCC stuff is easy to troubleshoot and keep running .. changed many drums in the old e-units


OK, so it looks like it was Possible Diagnosis #2 from my earlier note -- -- "The LCRU1 board failed in a way that it's still communicating with the RS2.5 board, but doesn't respond to any of the TMCC commands."

From what you've told me, your RailSounds board is acting like it should without the purple serial line attached to it, which is good.

There's really not much else that can be done, especially remotely. We know the LCRU1 is getting power because it's definitely sending the signal to prevent the RS2.5 board from starting when the serial line is attached. You've already pulled and re-seated the processor. I think you've confirmed that you've not had any lighting or movement throughout this whole process. Lastly, there's no way to perform a software reset/restore on those boards -- that feature started with the LCRU2.

Therefore, I'd recommend replacing the LCRU1 board.


TRW .. thanks, I reviewed the PC board to review if I could see any obvious component failure (ie: diode, resistor, capacitor,etc) and do not see anything, so it probably is the 18-pin prom (Lionel label LCRU 0412) with the LionTech program.

Re-thinking I did have a derailment the last time I ran the train and the SD50 was on the track, powered up, but shut-down via TMCC. The Powermaster did shut the system down, but possibly not fast enough .. just a thought .. I had not started up the SD50 after that last derailment until the other day

I see that that particular LCRU1 is still available from Lionel and I am thinking I will order one that is already programmed with the Liontech software.  Shawn (see note above) mentioned that the Motorola prom (PIC16C84) is available on line from China and I see them, but then the next roadblock is programming it. 

shawn posted:

There are schematics for these boards floating around....also, I've gotten some of those radio chips from china if you look around

One floating around in this post.

Lionel LCRU Schematic.pdf

Forget about programming the PIC.  Even if you have the programming tools (I do), you will never get the firmware to program it with from Lionel.  Oh, and it's not a Motorola part, it's a Microchip part.


Thanks .. I know all about proprietary firmware and respect the individual effort to develop it .. I meant to state Microchip  (https://spectrum.ieee.org/tech...6c84-microcontroller) as that is where I found it on my net search.

I will order a new LCRU1 board and move forward .. 

Thanks to all for help and suggestions .. at least I have some confidence that the Railsounds board is good 


To TRW ... Thanks for all the helpful suggestions .. at least I/we think the Railsounds board is OK as it is no longer available from Lionel .. the LCUR1 board is at least available for the moment anyway .. I would rather buy new from Lionel rather than an unknown state used unit off e-bay or wherever.


FYI to all .. I ordered a new LRCU1 for my SD-50 direct from Lionel as it was still available for $80, plus shipping and replaced it.. my SD-50 has been reborn and alive and well.. Thanks for all suggestions on how to isolate the problem.. I meant to update this sooner, but it had slipped my mind. 

FYI .. On the section of track that is protected by a Powermaster, I also had a relay for a short section of track just before a crossover such that if another engine was at the crossover, the relay would toggle from the mainline voltage of 18-volts for the section the SD50 was on to approx. 6-volts to stop the diesel yet keep the LRCU active so that when the other train cleared the crossover, the SD50 would toggle back to 18-volts and continue on without re-starting the diesel.. but that 6-volt power supply was not protected with a Powermaster .. I have since disconnected my 6-volt power source until I procure another Powermaster which responds extemely quick. The relay worked well many times, but obviously some level of risk .. another Powermaster should resolve

Greetings, I have been following your posts since I got more or less the same trouble as Larry had. You see, I have the same engine, It was bought used but running well in conventional mode  including the RailSound, I knew this from the beginning.  When attempting running it in Command Mode it was possible to addressed it with the ID number and get some responses such as light on / off, increase RPM, decrease RPM.  However when it came to move forward or reverse it did it erratically i mean with intermittent action. I made then a test on separated isolated loop wit the Base1L attached to it on the U post and the outer rail at the lockon device same outcome  with short circuit protection.

I recently bought a new LCRU1 as  following your posts and change it yesterday, but again, I got  the same performance . Nevertheless I after replacing the LCRU1 and testing it,  the sounds when on for a little while at starting the engine and then went off and work no more.  Now that I have  the schematics thnaks to you guys, I will review it all and check my the wiring connections. Then would come to you back for help or the share my experience anyway as Larry did.   

I can tell also bought  RD Teal Book  "Modern Toy Trains Repair and Maintenance " and using it as a guide. There I learned that pick up contact rollers are frequently overlooked and can make the difference in performance between command and conventional running modes.

I´d appreciate it very much any bit of advice, I´ll come back soon with my progress on this issue.

Many thanks



Arturo ... someone in the previous notes stated that there is an error in one connection of the wiring schematic and he is correct as my unit was wired as he stated .. I do not have the time at the moment to go back and re-check where his note was .. but follow his direction, not the schematic.. When my LRCU quit working .. NOTHING happened.. now all is well .. as soon as I replaced it, it fired right away .. the default engine ID with the new LRCU is "1" which was the ID I had previously assigned to that SD50 so there was no confusion with my other Command engines.

Good luck


PS.. Interesting in that when I called Lionel I told them that my SD50 6-18221 had remote front & rear couplers and they told NO it did not per their records and parts manual .. all I can tell you is that it does, they work and I bought the unit new in its original box and master shipping carton.


Hi Larry,

Many thanks for your advice and your shared experience. I can tell regarding the past info posted, that the addressed connection is the so called "violet" wire . I reviewed some of the above information  not all yet but I am certain that have the same card as yours,  meaning its the same  LCRU1 not sure yet about the sound card. The LCRU1 has indeed an option to connect to electric operating couplers that will should respond to TMCC commands from the CAB1  remote.  My engine has the conventional magnetic couplers as believe is the standard, these are to operate over the UCS track section only.

In regard to the violet wire connection, I can see so far, that there are only three input wire lines going into  the sound card ( I mean besides the two red and black from the stand -by 9v battery) these are the Red (AC-Hot) and the Black (AC ground), and the Violet. I mean, by default the Violet must be the data cable. The other cables are two and are the output to the speaker which are both Red. Then I think that if I interrupt the violet cable the sound card will only turn on and produce the RailSounds routine sounds,  but would not get TMCC orders to make the RPM increase, decrease, the shutdown sequence, etc. not sure yet how the horn and bell really work. Well that is just an hypothesis from me,  for now with my limited knowledge.

I heard from Lionel that they are moving their offices some where else and so will not attend any support demand until July 8th. This includes the support server, ordering parts, etc.

Well thanks again for sharing and for your time.

All the best





Arturo .. when I cut the data line to the LCRU, and went to conventional mode, the engine had lighting, forward neutral and reverse as well as horn and bell sounds but I do not think that I had diesel engine sounds, butt cannot remember for sure as it was late last year .


Good luck in your quest to resolve .. frustrating and half the fun, even better when you fix it (you learn a lot too)

Hi Larry

You´re  absolutely right, the post came from TRW, and it states that the violet cable was misplaced from factory for some boards at the sound card jack. This is, it should move one position where the red arrow points is the diagram. Maybe this is the issue I have had with the replacing LCRU1 board. I´ll check this out and post the outcome.

Thanks again


Hi Larry 

I am grateful to this forum for all I learned about this engine and other important things, so want to post something really relevant that because of the lack of knowledge can lead other members easily to mistakes and perhaps spoiling engines and other important part of train parts. 

You see, after dissembling my engine again putting apart both cards the new and the old,  I assemble it again this time following the diagram TRW gently shared. Fortunately the violet wire cable addressed  in the diagram was in the right position. However, when I attempted to  place sound card back by screwing it to the chassis I note that a sort of round threaded nut fastened to the card frame was loose and can not fix it properly so postponed its installation. So ran the engine alone with the new LCRU1 card only. It performed great in conventional mode I mean Frw / Neutral / Rev . 

When running it in command mode, was able to addressed it with #1 ; run fwd /rev turn lights on and off.   However I couldn't get it to run forward or reverse but just a very few feet, it stopped and made a hum noise just as before that I changed the LCRU1 card.  Although I could get it along the full layout on conventional mode one minute before.     I can tell at first, this was certainly disappointing and thought had not made any real progress at all changing the LCRU1.   I have many other engines most of them PostWar from 1950's and a couple Lionchief and these all perform very good until I got this engine which is actually my first TMCC / Legacy engine,    Then I believed found the right answer for this trouble; it is summarized in this video made by Lionel on 2011 about the TMCC /Legacy signal interference, here below find the link to it: 


The interference on the TMCC signal coming from accessories, adjacent track sections placed just too close to each other. Because these all share a common AC-ground which is connected to the Base-1L or Base-2 from where the TMCC / Legacy signal is generated. This interference stops the engine and switch it to conventional mode, the real cause for the erratic running trouble I had.  

I just wanted to share this link and make other mates aware about this interference issue for fixing it properly rather than changing cards and sending engines to service when they are OK.





Metal trackside, or over the track (signal bridges, and bridges) should NOT share a common ground with the track.  There have been numerous forum discussions on ensuring the TMCC signal is not negated by nearby tracks and accessories.  Search for "TMCC ground plane".

Interesting .. I really appreciate Arturo's and John feedback, including the embedded Lionel TMCC info link 

I currently am not experiencing any of these issues on my layout today which is 24x8 in my new house nor had I in my old house using the same wiring configuration as noted below and that layout was 24x13 .. Smaller room in new house .. very disappointing

I do see the merit in common grounding and potential for TMCC signal interference. When I put my 24x8 layout together and out of ignorance, I have a common neutral (or ground) throughout my entire layout and have tied all my transformers together with the same shared neutral, including my Z1, Powermaster, multiple transformers for my (30) 022s, lighting, signals, accessories, engine transfer table,   etc.. My common neutral uses a buss bar setup around my entire layout and therefore I only run a single power line (voltage dependent on what device I send it to) based on desired light brightness or speed of any given accessory.  When I have isolated rails, I typically only isolate one section of track then use the trigger rail to feed a small relay module that I make with a bridge rectifier with a 25V 2000+ mfd capacitor to a 12VDC relay to manage the AC voltage thru the relay going to the desired device. The capacitor smooths out any interruption when you have 'dirty' wheels on light cars passing over the isolated section and gives a steady 'extended' output.  If I run a block for example at a crossing gate and say the trip section is 4 track sections, I only use isolated sections in the 1st section and the last section and tie the two isolated sections together to trigger the relay. So any isolated sections is limited to one track length (I use Lionel tubular track). The same shared neutral is used on my 5 signal bridges and my Bascule bridge with no noticeable interference .

Now I only use one TMCC controller and I am considering adding another as well as a second Powermaster and Z1 to my layout as I am currently limited to running 2 or 3 engines concurrently before my Powermaster trips out from current load .. (it all depends on the engines running and their motor configuration (can motor, Pullmor single or dual motors, etc). So this awareness of signal corruption may make me think different on this addition 

   Thanks again to all

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