Engine: MTH 30-1220-1 RailKing 2-6-6-6 Steam Engine: BCR equipped

DCS Operations: TIU/Remote version 6.10

Transformer: Z1000

Track Voltage: 18V

Issue: When operating my MTH 30-1220-1 RailKing 2-6-6-6 Steam Engine the engine lighting is dimmed when the smoke unit is operating.

The light on the front Cattlecatcher and the Firebox lights are controlled by the LIN option on the DCS remote. The "Headlight" is inside the boiler shell and lights the marker lights. The "Headlight" is not controlled by any options on the DCS remote.

At startup with the LIN option "ON" the lights are all bright with the Smoke Unit operating. The lights pulse slightly with the chuff of the smoke unit. When I turn the Smoke Unit "OFF", the lights are bright and the pulsing stops.

When the engine starts moving and with LIN "ON" and the Smoke Unit "ON", the Cattlecatcher and Firebox lights begin to dim and by 6 or 7 feet of movement they are barely visable. If I turn LIN "OFF" the lights are still dim but brighter than with LIN "ON". The "Headlight" seems to be affected only slightly.

When I turn the Smoke unit "OFF" while the engine is moving, the lights are back to bright.

I have taken the shell off the tender and off the engine looking for loose wires, signs of electrical shorting, and have found nothing. I tightened all the wire nuts that I found. I also ran the engine and tender without the shells looking for any signs of electrical shorts and found nothing.

The wick in the Smoke Unit looks "normal". It is white and is not black and hard. The Smoke Unit works well.

Anyone have any idea why my lights are dimming when the engine is moving and the Smoke Unit is operating.



Original Post

Just wondering how are the track power conditions? Do you have lighted pass cars on the rails? Do they also dim when the smoke is on?

Can you test with power hooked up directly to the engine on your workbench? or just a short piece of track?

Have you used the remote to look at engine track voltage while running?

" on Sour mash and cheap wine " ??

Why go back to DCC when I have DCS!

I forgot to mention in my original post that this is a PS2 engine.

I have taken all the other cars/engines off the track and got the same results.

I don't have a workbench or test track set up so I can't test that way. What type of bench testing for this problem would you recommend if I were to set something up?

I also don't know how to display track voltage using the remote. I ran the track conditions test and the DCS signal is a 10 all the way around my 4X8 loop.

When I first start up the engine, the LIN is off. I turn on the LIN and the Cattlecatcher and Firebox lights are bright but very slightly pulsing with the Smoke Unit Chuffer. When I start to move the engine, the lights stay bright for a foot or so and then start to dim (like a capacitor is discharging maybe?). They stay dim unless I stop the train (Smoke Unit still on) or when it is moving and I turn off the Smoke Unit. When the engine reaches 0mph the lights immediately brighten. When the engine is moving and I turn off the Smoke Unit, the lights immediately brighten.

Here is a summary of what I see:

Engine startup: LIN off, Smoke on: no lights

Engine startup: turn LIN on, Smoke on: lights bright (first pic light in front, second pic firebox)

Engine moving first few feet: LIN on, Smoke on: lights bright

Engine moving after first few feet: LIN on, Smoke on: lights dim pulsing (third pic light in front, fourth pic firebox)

Engine moving after first few feet: LIN off, Smoke on: lights dim but steady (fifth)

Engine moving after first few feet: LIN off, Smoke off: no lights'

Engine moving after first few feet: LIN on, Smoke off: lights bright (sixth pic light in front, seventh pic firebox)

Engine stopped (after running around track): LIN on, Smoke on: lights bright

Hope this helps.



Photos (7)

There is a service bulletin for Premier Challenger with the 5V board and a mux board in the locomotive to fix that exact issue.  I wonder if a similar issue exists with the RailKing Challenger.

I think my first step would be to make sure there are no loose connections in the locomotive or tender, it appears when the smoke unit is drawing current that you're losing a lot of voltage to the lights.

The MUX board fix is for flickering lights when the smoke unit is on.  Something is pulling down the PV voltage.  Either the smoke heaters are less than 8 ohms (combined), they are shorted to the housing, or a bad ground back to the board through the harness, thether, or socket.

Jon G TCA 95-41020

Independent Lionel Service Tech

MTH Service Technician at MTH

I agree that something is pulling down the voltage to the lights and it has something to do with the Smoke Unit.

To be clear, the LIN lights do “flicker” with the Smoke Unit but they are also very dim. The lights are also on when LIN is off and the Smoke Unit is on and the engine is moving. Weird if you ask me.

I’ve checked all the wiring I can. I’ve taken the engine and tender shells off and followed all the wiring I can. Sounds like I’ll be making a trip to the MTH service rep 

Thanks for the info. If anyone knows any other ways to check this out, please let me know.

BTW there is a board in the engine that the lights are connected to. I could post a pic if it would help.



I've had 2 MTH engines do the same thing, one recently. 1st one the 5volt board was going bad. 2nd one, a 2-8-0 also a 5volt board I sent to GGG on a Monday. He indicated a short and installed the PS3-2 board. I had it back on Sunday. Amazing fast work, both have the new boards installed with no problems. GGG also returned the BCR I had installed. I highly recommend GGG for any work. 110% satisfied with his work.

What to me is amazing about these 5 volt boards how easy they go bad with no short, etc. Worked great, both the day before. Then next day after just sitting, develop problems and go bad.

I would check with  vom meter for continuity and check as described below I would disconnect the smoke unit completely disconnect the electronics   check for shorts to case of smoke unit to heater should read infinity! heaters should read 8 ohms but not  less. do you still see 18 volts when all features are on under load? if not set to 18 volts while all features are on! what is your current draw with smoke on and smoke off how much voltage is dropped with smoke unit on and off!


o gauge  trains ,music ,computer repair windows 7 and 10!

ASC Tech MTH school completed! 2019 !

If it has a MUX board and a 5V PS/2 board, it's very possible it's the same issue as covered in this service bulletin.  This was issued for the Premier Challenger, but it turns out that a number of different PS/2 locomotives have the same issue.  I have one in now, the Greenbriar, exact same issue.

PS2 Steam Light Flickering With Smoke.pdf


Thanks everyone for your inputs and suggestions.

I took the shells off both the engine and tender today. I disconnected the Smoke Unit and tested it with my VOmeter for shorts and measured the resistance. I could find no shorts. The resistance measured at 8ohms or slightly higher (no higher than 9ohms). I saw a voltage drop of about 0.5v (17.5 vs 18.0v) when all features were turned on under load (I have an analog VOmeter so it is hard to be exact). I  don't have the tools to measure the current draw on an AC circuit. When I ran this steam engine and a diesel engine at the same time, the voltage dropped to about 17.0V.

I then took off the wire nuts in the engine and checked the wire connections. All the wires were twisted tightly. I then replaced the wire nuts and tightened them securely.

I disconnected all the PC board connectors I could get to in both the engine and tender. This included the board in the engine as well as the main board and another board (MUX?) in the tender. I inspected all boards for signs of shorts and the connectors for possible bad connections to the connector pins (none found). I then re-seated all the connectors in their respective boards.

After putting the shells back on, I tried out the engine and tender on my track. The lighting was much better but still has problems.

LIN was on and the lights very bright when I started the engine and it was sitting in neutral.

When I started the engine, the light stayed bright for a while (thought I had it fixed but read on). After a trip around the layout, the light had dimmed (but not as much as before today) and was pulsing (it isn't really a flicker but it depends on your definition of flicker).

When I changed the LIN to off, the light became steady and was definitely brighter than before today, but still dimmer than when sitting still in neutral.

I then turned the Smoke Unit off and the lights went off until I turned LIN on. Then the lights were back on as bright as the engine sitting in neutral (the engine was moving around the track with smoke off and LIN on.

When the engine stops with LIN on, the lights pulse as the engine runs slower and slower. At about 4mph the lights go out. At neutral (0mph) the lights turn back on quite bright.

I'm thinking I have a board problem but I don't have the skills nor documentation to determine which board(s).

It's strange that LIN on/off act differently depending on whether the engine is moving or in neutral.

I'm still hoping I can figure this out with your help, but am about ready to take to a repair shop.



I did look at the service bulletin. Sorry I forgot to mention it in my last post. The only part of the bulletin I can implement is step 1 (swapping the royal blue wire pins). I haven’t had time to make the change today. I’m hoping to make the change tonight or tomorrow. 

I don’t have the skills to implement steps 2-4. If I do take it in for repair, I’ll be sure to mention the bulletin.

Thanks for continuing to follow this post. 


I've fixed a few of locomotives with this issue using those steps.  I only had to do the first two steps in a couple, but I have also had to do the whole deal on a couple.  I have to get to the Greenbrier to see what it's going to take.

I've tried to implement step 1 of the Service Bulletin and ran into an issue. When I try to swap the pins that connect the royal blue wires going to each connector, the royal blue wires are not long enough to reach the connector for the other board. I really don't want to start cutting and soldering new wire.

Am I missing something?



Thanks gunrunnerjohn my engine is now fixed due to your suggestions.

I decided to brush off my wire splicing and soldering skills and implement step 1. I also made sure to disconnect and re-seat every connector in the tender.

I just ran a test and the lights are bright at all times, no flickering, and LIN on/LIN off work as they should.

I'm not sure if re-seating the connectors did the trick, swapping the Royal Blue wires, or both but I'm happy it is working again. I tested the all the features using DCS and all checked out. I'll be running it some more in the next few days as an acid test.

Thank you and everyone else that replied to my post.



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