Runaway PS2 engine

You're gut is pretty much correct.  That's usually the tape or sensor, loose connection to the sensor, or the amplifier on the PS/3 boards.  Is this a 3V or 5V board set?  The 3V board set has an easily accessible chip that sometimes fails and can be replaced.

If GRJ's suggestion doesn't work, try a feature reset, and if that doesn't work, a factory reset.  I had one older (2001) PS2 (5-volt board) that occasionally would do what yours done.  A reset would cure the problem for a time.  After several occurrences I installed a 3-volt board.

Another cause could be a loose flywheel.

Thank you for the thoughts. 

It is a newer (3 volt?) board. The tape on the flywheel appears to be in perfect shape and I have already done a factory reset. I tried pressing the connections into the board to insure good connections there. 

I am making a trek to the Trainz offices today to pick up a recent purchase. I'll let their tech have a look. He has replaced some capacitors for me in the past saving a 5 volt board. If gunrunnerjohn's idea about a bad component on the board is correct than maybe it can be repaired. 

Quick follow up question: since I have had a few experiences like this already, what do you folks use as a circuit breaker between MTH DCS or Lionel TMCC/Legacy systems and the track. I believe derailment shorts are triggering all my board issues. 

Best, Scott

Scott, the old 5-volt boards are failing.  Posts indicate that there were bad capacitors being produced overseas about the time they were issued.  Probably has nothing to do with derailment shorts.

I use 5 and 7.5 amp breakers between transformers and TIUs.  I get them from marine supply houses, for about $6 each.

I use the Lionel Powerhouse 180 transformers, they have a really excellent electronic circuit breaker that is very fast acting.  The TIU also has a TVS across each output for spike protection.

Could the gap between the tape and reader be excessive and cause the runaway problem?

Yes,  also the tach reader can just fail.  For steam the harness having an open on the tach circuit is also a likely culprit.   G

Howdy friends!

I have a Premier Dreyfus Hudson (3 volt board) with the same problem. Already tried a new tach reader. All your input is very welcome.

Merry Christmas to ALL !

doc

Doc, if you've CAREFULLY checked the wiring all the way back to the PS/2 boards, the likely suspect is the amp on the power supply board.  I stock those and it's a fairly quick fix.

Before assuming it's the PS2 boards, pull the 12-pin connector and ring the wires out through the tether right from the tach reader to the 12-pin connector and see if they're all present and accounted for.

Take both shells off, place on bench with tether connected.  Check continutity between tach reader gray and either 4 pin gray or 7 pin gray, orange to 7 pin orange, blue to 7pin or 12 pin blue.

If this has MUX board it gets more complex but you need to trace wires to make sure good continuity.  Especially through the harness.  If that is all good, the Power SUpplu board needs to be test.  You can swap another in, or send to tech.

If that is good, and gap is good on tach read, change it again.  I have seen a new one not work on occasion.   G

The tech at Trainz determined it was a blown op amp as GunrunnerJohn had suspected.  Nice call!

Yep, That is the Power Supply board.  Did he fix it or replace with new power supply?  The fix is much cheaper.  G

The technician replaced the failed component on the board.  I brought the engine home last night and gave it a test run.  The engine ran fine at first, but before it made a complete loop around the track, the problem resurfaced.  Darn!  

The repair wasn't inexpensive (approx $100), and I fear the problem may have another root cause.

I use Lionel FasTrack and the only "unusual" features of the area where the problem occurred are a track powered O36 Powered Remote Switch which connects this end of the layout's dogbone loop and a KLine by Lionel SuperStreets Fastrack grade crossing.  I examined both and I see no obvious problems.  The Superstreets loop is also a dogbone and it is powered by a Lionel 40 watt transformer.  Although power was applied to the SuperStreets loop, no cars were running at the time.  The railroad is powered by an MTH Z4000.  Both are plugged into the same powerstrip so I believe continuity is not a problem. 

Anyone have a thought?

Wow,  First a new Power Supply is only $80 MSRP.  My component repairs are much less for a Power supply board.

Either a leg or 2 on the chip is not soldered fully (cold joint), or you may have a wire harness issue. Would explain come and go for the issue.

I am sure TZ will take care of it under warranty.   G

By all means, send it back to TrainZ, obviously something else is happening.  $100 isn't cheap for that repair FWIW, or I don't charge nearly enough!

But are the transformer correctly phased?

 Both are plugged into the same powerstrip

RJR,

I will check (assuming I know how!). I will most likely switch both systems to the same transformer to make sure they are in phase. Idiotproof is always a good plan for anything I am involved in.

A couple of questions:

Since the the plugs of both transformers are polarized, how likely is it the the Lionel and MTH transformers are out of phase since they are plugged into the same outlet and powerstrip?

Assuming they are out of phase, how do I correct this since the polarized plugs will prevent me from turning one around?

Thank you all for your input!

Connect the commons of the two transformers together, set them to half throttle, and connect an 18V bulb between the "hot" terminals.  If the bulb is bright, they're out of phase, if it's dim, they're fine.

In answer to your question, Longhor, you could (1) get a cheater plug into which your current plug fits; (2) install a new plug on the end of your current cord, with polarioty reversed (before doing this, I'd use an ohmmeter to make sure neither prong has any connection to any metal on the transformer; if it does, I'd not use that transformer at all); (3) open the transformer and reverse the cord; (4) use one transformer.