TAS Engineer On Board Problems

Hi, I had a question about the TAS Engineer On Board cruise control. I had installed the system several years ago on a K Line FM Train Master. It ran smoothly in 128 step, 32 step and non cruise modes. I recently got it out after some years of not running and now in cruise mode it goes instantly to fast speed. In non cruise mode it still runs smooth. I read the manual again and some forum posts here and both lead to the optic not reading the tach tape correctly. I replaced the tach tape using the pdf available on this forum (Thanks gunrunnerjohn). As best as I can tell I have lined up the black ends evenly & the optic is triggering at every bar. The engine started slowly the first time, then took off for a short distance and the horn sounds continuously. It still runs fine in non cruise mode. Not sure where to look from here.

Original Post

The symptoms suggest the board is indeed going south.  I have fixed several of mine, but they're getting long in the tooth, and it gets harder to justify keeping them running.

He stated that the LED is blinking for each stripe on the flywheel when he rotates it, so I suspect it's probably close enough.

"As best as I can tell I have lined up the black ends evenly & the optic is triggering at every bar."

Thanks for the quick replys. I'll try setting the sensor gap again.  I have couple questions still.

First: does the sensor see the white or black or does it really matter?  Looks to me like the red LED is actually turning on, on when the white part passes (gets its reflection). I imagine the EOB only cares about regular pulses from the sensor board.

Second: is it usually the sensor board that fails or the main board?

The sensor just converts black and white to ones and zeros. This is a reflective sensor so white reflects the light back and turns on the photo device (transistor, diode?? doesn't really matter) on. I assume you are seeing the red LED with the shell off. If you run it at speed is it still blinking at a regular rate or does it stay off or stay on?

All the failed EOB boards I have seen fail around the power devices including vaporized circuit traces. Never had a problem with the tach circuitry other than adjustment.


I've actually had several that ate their uP, which is a show stopper.  However, the triacs and the power traces are the more common failure.  Those are not that difficult to fix, but it's a PITA to fix the triacs, you have to pull the whole works off to get to them.

Norton:  At a crawl in cruise off mode the red LED appears to be blinking consistently anything faster and I can't tell.. might be because the motor is turning too fast for my eye. 

Gunrunnerjohn: Do the triacs stick on? Is that why the engine takes off at full speed?  The engine runs fine in cruise off mode - no full speed take offs. 

First off, check the wiring between the tach reader and the EOB motherboard VERY CLOSELY!  I've seen a number of them that have a broken wire between the two units, if the signal wire is broken, you'll get the rocket effect.

The fact that conventional works is simple to explain, you're just passing the variable voltage through, even if the triacs were shorted, it would still run that way.

Usually, only one set of triacs is bad, though I replace all of them if I have to remove the heatsink.  That being the case, the locomotive will frequently run properly in one direction, but take off in the other.

The Horn and intermittent running suggests a control circuit issue.  I'd remove and replace the PIC processor in it's socket to make sure it has good contact, and I'd try a different R2LC. 

It has been runing fine in command mode cruise off. I reseated the PIC, don't have another R2LC around to test right now.  After I reseated the PIC, I noticed the tail of the tach tape had lifted, so I glued it down. After that I ran it forwards and backwards for about 20 min each direction in the first speed step. I need to  run it more and at faster speeds to see if it stays good. 

Reseating the PIC was probably the silver bullet, after some years, the contacts tend to oxidize and cause issues.  The same thing happens to Lionel RailSounds audio boards, reseating the two chips fixes a lot of these.

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