run away lionmaster big boy HELP PLEASE!

Past experience tells me the motor driver board is the problem. Might try a known good radio board first, just that it is easier to start with, then if problem persists, it's the motor board.

thanks chuck I will try that.

chuck btw, what could have caused the motor driver board failure? assuming thats what it is.

I start with the wiring between the flywheel sensor and the motor driver board.  I agree that the motor driver board is probably the top suspect, but it's also the most expensive of the causes to fix.   If you decide you need it, you might wait for the annual Lionel 1/2 price parts sale to pick one up, $55 instead of $110.

I'll 3rd the motor driver board. My father has the exact same Loco and it exhibited intermittent surging for a long time.

He tried solving it by cleaning the track etc, until it finally got worse one day and bound up one of the gearboxes.

I  sent it to Mike Reagan who replaced the motor driver and dad feels it now runs better than it ever had.

LionelZW, I wish I knew what causes these boards to fail. The problem is no-one knows why it happens.

I've had several that had cooked drivers, those were easy to fix.  However, others had drivers that tested OK, and they still ran away.

If it's the tach sensor, the locomotive will go a few feet and then stop as the driver board senses that it's not getting any tach pulses.  If it just takes off and never stops, it's probably not the tach sensor.

 I wonder how overdesigned the motor drive board is. Seems like frequent failures says that mechanical stalls of the engine might damage the board. Stalled, the motor will draw maximum current.

And...I find myself having already impatiently ordered parts and have nothing left on the list during Lionel’s half price weekend. I seem to do everything within 8 microseconds of thinking of it. Wish I could have more patience!

thanks for all the input here guys. 

about the 1/2 price parts sale john. when ordering online how does one handle parts that say must contact lionel to order? anymore I just order online instead of by phone. 

There was a procedure to do that, but this part we're discussing isn't one of those anyway.

I should have clarified my question better john. I also needed a fan motor control board for my visionline genset. might as well get around to getting it also when the sale happens. it was the must contact lionel to order item. 

 guys, also I was looking at the traction tires for my big boy and it states unavailable.  so I checked another legacy big boy on the parts list and they are available. only thing is they are different in size. I would have assumed they would both be the same. the machined wheel grooves on both models must be cut different. perhaps because of different production runs. hence the two different sizes. since my exact models tires are unavailable. which set must I order that will replace my old traction tires? 

Just call and they will give you the substitute traction tire.

thanks ricko

When is the Lionel half price parts sale?  Is it at the same time each year?  If not, how do you know when the sale is? 

Thank you, Janet (TCA and LCCA member)

Janet Mattern posted:

When is the Lionel half price parts sale?  Is it at the same time each year?  If not, how do you know when the sale is? 

Thank you, Janet (TCA and LCCA member)

Same weekend as the Lionel warehouse sale. I've gone to the last 2 and they're usually the first weekend in November. I've already planned for the 2nd, 3rd, and 4th of November this year.

Typically, right after the fall York Meet.

Lionel is out of the motor driver board, any idea where I could find one or can these be repaired?

@Casper posted:

Lionel is out of the motor driver board, any idea where I could find one or can these be repaired?

Lionel deep-sixed all those early Legacy and TMCC boards, there will be no more.  You'll need to try to get it fixed.  A runaway is frequently the driver FET's, those can be replaced.  Another common fault is the wiring or motor tach sensor, look that over carefully.

Do you happen to know the part number for the FET’s?

My 6-11149 Legacy Big Boy was also having the same issues with it frequently taking off, like it was on full throttle. I just took it apart last weekend and could not see anything wrong. I tried cleaning the contacts and reseating the R4LC board. Finally I took the two wire nuts off on the top of the chassis one at a time. And inspected the wires. There was a grey wire that had broke off inside the wire nut. The wire nut was probably screwed down too tight when the locomotive was assembled from the factory. I removed a little insulation of the wire, and put the wires back together with the wire nut.  I have tested it many times and it has not done it again. But I still do not trust it yet.

My 6-11149 Big Boy did the same thing again, started intermittently speeding up like it was in conventional on full throttle. I took it apart again, and started unplugging plugs and plugging them back in repeatedly to self clean the plugs and their connectors. I also sprayed tuner cleaner carefully on the plugs, to help clean the contacts. A trick I learned working on VCR's and a camcorder. While I was doing this I found a small plug on the back of the motherboard, in front of the motor control board was only halfway plugged in. I self cleaned that little plug also, and the plug harness. I plugged it back into the motherboard securely, and my Big Boy has not malfunctioned again as of yet. I have started it up and run it at least twenty times or so, and so far so good. Try self cleaning your plugs, and connectors. Being careful not to pull on the wires very hard, take your time.  And be sure that every plug connection on that chassis is properly plugged in. Maybe it is not a malfunctioning board after all, rather poor connection. Its worth a shot

Thank you for the information, I appreciate it!