The circumstances are as follows:
-I saw both locomotives operating correctly under DC control with blanking plates fitted.
-When I got the locos home took out the blanking plates and put in the Bachmann chips, both locos "ran away" as soon as placed on the DCC programming track.
-I attempted to reset the chips by placing the locos on a rolling road.
-Both locos then became completely unoperable.
-After putting in replacement Dapol chips, both locos now cause the powercab to short out.
-i have stripped one loco down completely removing the bogies and motor and connected the circuit board to the progrqmming track, with the same resultant short circuit.
-I now have nearly £600 of inoperable train set

Really at a loss as to what to try now