TMCC

Please consider changing your title to some thing like, "TMCC runs off when power is applied" you will get more answers.

try putting your hand over the engine and see what happens.

there are a lot of people that will help they just need to know what the topic really is.

It sounds like the speed encoder is not functioning.  Does it start before doing anything, or when you first try to move the throttle?

The locomotive starts in forward as soon as I bring track power up above a certain level.  If I reduce the power, it will stop, and if I increase the power to maximum it will take off at high speed.  I have Legacy control with a ZW controller and four 180 watt power packs.  It doesn't respond to any commands except the panic button, but that shuts the power off to everything.  It seems to be running in conventional mode, as it starts as soon as track power is brought up.  If I remove it from the track, I can power up the track and  address the other locomotives by pressing eng and the ID, and they function normally as I bring up the throttle.

Odyssey speed control could have fractured.  without the magnetic ring there isn't any mechanism to do closed loop speed control.  The motor will just run at max speed.

Even with a fractured magnetic ring, why is the engine moving as soon as power is applied if a Command signal is present?  Should still wait to be started up and movement signaled.

To me it sounds like a Motor FET(s) have shorted and track power goes straight to the motor hence why it moves immediately when track power is applied and proportional to track power, with no directional control.   G

I just retested it with the engine off the track and using test leads.  The engine starts running as soon as track power is up.  I have the ZW control handle set at about 19 volts.  The engine runs and the lights are on, but there is no reaction to command signals, either in run or program.  If I manually reduce the voltage using the ZW handle, the engine shuts off below about 10-12 volts, and if I move the handle up and down, the motor reverses.  I noticed that sometimes it just runs at low speed, and then at other times it runs very fast and then slows down and runs at the constantly at the lower speed.

It's apparently starting in conventional mode, the fact that it reverses makes that likely.

You have some issue with signal reception, I'd check the antenna to see if it's shorted to anything or disconnected.  Also, you might try swapping the R2LC with a known working one.

I would pull the R2LC board and reseat it.  Pull the plugs out of the DCDS and replug them.  It has to be something simple.  Not knowing what engine you have, try this for steam.  Put the test leads from your meter on the locomotive handrail and ground if it is steam.  If you have continuity you have to find out what is touching ground.  John is right on the R2LC, it seems your locomotive is not seeing a signal and responding in conventional mode.  Again, throw out what your locomotive is.  Your flywheel encoder board might not be seeing 5VDC.  I received the above information in an email, but didn't see it on the forum page??  What am I missing?  The engine is a 4-6-2 Pacific that was part of the Blue Comet set made in 2001.  I bought it new in the box a few years ago, and just unpacked it.  It started up fine a few weeks ago.  I checked the hand rail and it all appears correct.  I couldn't do a continuity check because the rails are very well painted and don't conduct.  Regarding the suggestions, I'm not sure how to take the locomotive apart to get to the inside, which I'm happy to do if I knew the routine. Thank you and Happy New Year.

Franz, I have that engine also.  Scrape a bit of the paint under the handrail to get clean metal and then check continuity with ground.  If you have continuity, you are at the cause of your problem.  After you do this check, touch up the spot with a black magic marker.  Next pull the body and look for a loose R2LC board.  That is not uncommon.  Like John pointed out if you are starting in conventional your locomotive is not seeing a signal.  Please do these two things and get back to us.  While at the R2LC, replace it with a known good one for testing.

One more thing to check, with the body off the locomotive, check the antenna and pin number 23 on the R2LC board for continuity.  At this check, you do want continuity.  If you do not have continuity, let us know.  Pin 23 is on the bottom row on the far left looking at the board from the back side.

Rechecked, and the handrails are not grounded.  I don't see any obvious way to remove the body and am nervous about damaging unit.  It's pristine at the moment.  Can anyone point me to an instruction on removing body?  Thank you.

My loco is packed away.  I am sure someone has one they can send you a photo of. 

Do you have an actual model number?

72-8066-250

Looks like there are two cab screws in the rear and a single one in the front.  This is from the User's Manual for the locomotive.

I normally remove the pilots when I take the cab off, makes it easier to work on it, at least for me.