Spectacular TMCC Base Blow-ups

Dale did those units come from a place that gets a lot of lighting?

LOL, You would be surprised to find how much 120 V AC is under the layout and gets plugged into the wrong spot!

I have seen a QSI board that the engine had 120 place on the track.  Interesting enough I cleaned off all the slag and the board still functioned!  G

Rensselaer, NY

The bases were connected to two separate display layouts, which probably means the problem wasn't caused by a goof on the layout, but rather something systemic with the power or lightning.

I believe the Lionel output capacitor is only a 50 volt part.  Seems like a 200 volt part would be better insurance against any problems with 120V AC on the track, but that would take more space and cost more money.  The impedance of that .1 uF capacitor is 26Kohms at 60 Hz, probably high enough to not have huge currents (6mA at the peak of the 120V sinewave) if the capacitor dielectric doesn't rupture.

None of this seems to explain how they became so damaged on the output side.  Clearly it required high current for the type of damage on the regulator, no?

Dale,

It almost sounds like a transient surge in the outlet (s), was there any surge protection on the power supply? A lot of these issues I read here seems like it's caused by a flux in the household power. Any thoughts and would you recommend surge protection? I am surprised that no one ( in many issues related to sensitive electronics) mentions this possibility.

I have whole house surge suppressors in each of my 200A panels to stop most of these things at the door.  Not perfect protection, but at least it's an attempt.

I did get a bit of additional information:

The two Bases were on two modest sized layouts in a basement. 

Each layout is powered from a plug strip that was OFF.

One layout also has a DCS TIU that was not damaged.

There was no other damage to any household electronic devices.

The raw power to the layouts comes from MRC transformers.

I am still scratching my head.  I can visualize a spike coming in on the "U" thumbscrew terminal, zapping the coupling capacitor, frying the track signal output transistor, and then spiking the power supply bus to kill the regulator chip.  The earth ground connection through the wallwart would still be in place even with the plug strip turned OFF.

I have a hard time seeing a pulse from inside the Base that would be big enough to fry the output capacitor, especially with the power strip turned OFF.

I've had a lightning strike that took out all sorts of stuff all over the place, including appliances and electronic equipment that was turned off by a power strip.  Electricity is funny like that.

You would think a lightning strike we be noticable to the owner.  Even if not at home, other items effected.  Funny that you have 2 devices from 2 different folks that are identical in damage though.  G

They are both from the same fellow.  Both layouts are in his basement.

Could it have been from power that somehow came in via the "ground" circuit?  Backward so to speak, thereby avoiding the spike suppressors on the inbound leg?

One thing is for certain, there was power involved!