jim bro

hello,
I am trying to remote control a stepper motor.For receiver i use a receiver module with a decoder HT648L(Holtek).Because my stepper is unipolar my driver has a translator(74ls157 as multiplexer and 74ls74) and 4 transistors tip110.I have a strange problem:Everything work fine,when a hi appears in decoder's out the translator works perfect and the driver with the transistors too.But everything works fine without the stepper motor.When i put the stepper in the driver output happens something that i cannot explain.When i give a hi from the transmitter at the receiver,at the decoder output appears a hi and the stepper starts working.But when i give low from the transmitter at the receiver there is again hi so the stepper keeps working.Can anybody explain it?