Tortoise switch machine power supply problems - Model Railroader Magazine

   Hard to say.  Your total tortoise load is somewhere between 320 and 400 mA which is less than the 500 mA rating of the power supply.  You might try looking for a beefier power supply, just on general principles.  Or it could just be bad luck.  If it's going to fail, electronic stuff tend to fail when young as defective parts let go under load.  After running for a couple months, it will most likely run for years and years.  How long had your power packs been in service before they croaked?  couple a weeks? couple a months? couple a years. 

   Could be a lightning hit.  I lost the 12V 500 mA power supply for my router in an electrical storm.  

   The bulge in the case suggests a part, perhaps an electrolytic capacitor, blew up but the bang was contained by the casework and potting compound.   Manufacture of electrolytics is not well under stood, the industry has suffered from batches of bad electrolytics for years.  The first one I heard of was the GE CL65's on the antiballistic missle program back in the early 1970's.  Last one was a bunch of tantalum jobs going bad at Teradyne in 2003.  Were both failed units from the same maker?  If so, the maker could have had the bad luck to put a batch of bad capacitors into his entire production run before noticing the problem.  

    You might check the voltage out of the wall socket.  Should be between 115 and 125 VAC. Every so often bad things happen to house wiring and voltage goes way out of limits.