This video demonstrates the unloaded amperage draw between a common 6 ohm Tomy SRT armature and an aftermarket 0.10 ohm (that’s one tenth of an ohm) armature. For the 0.10 armature, the power supply could not generate maximum 18 volts due the higher than 3 amps the armature was demanding. This is an extreme example but demonstrates what happens with more common 2.8 and 2.5 ohm armatures and cheap factory 1/2 amp power supplies. An armature can peg the amp draw to where the transformer can’t deliver voltage.
Youtube Link
