EOB fails in reverse-Problem(s) Found

Assuming that the engine has no mechanical binding when turned in reverse, I would think that something is wrong on the motor driver board.  Not completely familiar with TAS.  Is this an AC motor or DC motor engine?  G

G, All 3rd Rail engines use DC motors. TAS uses unique motor driver boards. I am hoping the continuous whistle after stopping in reverse is a clue to pinpointing the problem so I can avoid ether replacing the EOB board or opening the engine if I don't have to. I have done both but its a chore I don't look forward to.

The engine does move in reverse but only for a few inches so I suspect the board is not completely dead. Turning the power off and then back on and addressing the engine I can move it back a few more inches so I don't think its a mechanical problem but can't rule it out yet.

Pete

One I had with a continious whistle meant defective and had to send it back.  Tas is junk, I have one engine a shelf queen because two tas units went out and no more warranty. 

Top suspect here would be bad drivers, however that will not only require opening up the unit, but also some interesting surgery on the TAS board.  I've done a couple of these, and it's a bit of work.  You end up replacing all the drivers, as you have to cut them away to remove the heatsink from the PCB to access them in the first place!

The TAS stuff was not made easy to work on...

John, BTDT. I agree the power devices were not meant to be easily serviced. I have spare boards but the engine appears to have little or no run time based on driver and roller marks (none). All of the electronics are in the tender (save speed sensor) and I've had that apart already to replace the R2LC only to rule that out as the problem. Swapping boards is still a PITA though and I am still hoping to avoid that.

Pete

Well, if it's not the R2LC, and it's not the motor or mechanical issues, you're not left with much.   Since I've had two of these TAS boards eat the drivers, they're usually my top suspect.  It could be some other component on the TAS board, but since that's the whole motor drive exclusive of the R2LC, you're still looking at the same component.

One thing I'll mention.  I've seen an encoder have a problem with one direction of rotation, even though that seems not to make sense.  That might be a possibility. 

I believe the whistle blowing is the tach sensor alignment;  Maybe worth a look to see if this sensor has moved; with the motor thrust, it is possible to be out of alignment in one direction.

If you have excessive thrust movement in the flywheel when changing directions, this could cause enough sensor misalignment to lose feedback/control. Might be worth looking at. I had this happen with something, can't remember what...it's been a while...

Edit: I just read what Jon wrote..

Acronym translations for us uninformed observers:

TAS: Train America Studios

A recent addition to our 3rd Rail models is E.O.B. “Engineer On Board”, Cruise Control.

from  http://www.3rdrail.com/images/cat0908.pdf

Thanks everyone for all the ideas. I'll pull the shell off tonight and check the tach sensor and flywheel.

Pete

The sensor should be easier to fix than the drivers.

I overlooked the whistle blowing comment in your first post.

Ok, I took the J3a Hudson apart. I found two issues that could have contributed to the stalling. The first and most likely was a misaligned tach sensor. The sensor is mounted to a metal bracket that is screwed to the frame. The holes in the bracket are threaded to accept the screws but I also found the frame holes that the screws passed through were threaded??

The fix was to drill out the threads in the frame so the screws could tighten the bracket to it. I also found one of the valve gear rods was bent fairly severely which caused the wheels to bind. Luckily the metal was soft and I was able to get it close to straight but not perfect.

I had to resolder some piping as well. I think some previous owner had tried to repair the engine and was a little ham fisted in the attempt.

Anyway all's well that ends well. No complaints as it was still a bargain.

Pete

That sounds cheaper than ripping the boards apart.   I'll have to remember that horn clue, that was mentioned a long time ago and I forgot all about it.

I would be interested in why the whistle is linked to tach sensor for these?  G

I can only speculate that some of the error codes are expressed that way, not unlike blinking cab lights in Legacy. Maybe Mike R or Ernie could fill us in on any other audible indications of errors.

Pete

I suspect it was just annunciation of the tach error.  They could have blinked the lights, but that's already taken for indicating weak TMCC signal.