RadioShack 6V 1800mA Adapter Won't Start DC Motor With Wall Timer—Why?

I built a very simple circuit: a digital AC wall timer that I plugged in a RadioShack 6V 1800mah transformer/adapter, then the adapter DC wires connect to a 6V DC motor.

Simple, right?

BUT. When the wall timer switches on the motor won't start. If I open the circuit (ie disconnect a wire), then close it (reconnect the wire), then the DC motor starts.

I've switched in a different transformer and the problem does not occur, so clearly it's the RadioShack transformer.

BUT WHY would this happen? Is it some kind of capacitor type or relay issue in the transformer? It makes no sense to me, just a simple, humble, mechanical engineer 

The reason I strongly prefer the RadioShack transformer is it is 50% smaller than any transformer I've found for sale stock off theshelf. So if there is an easy fix to correct this non-start open/close circuit issue so I canuse the RadioShack transformer that would be ideal.

Thanks for any help or advice!

Hi Garrett wilson,

I think it may be due to the lack of switching pulses for the switching transistor

change base resistor , cap coming in the base ckt blindly change it it may show good

in the meter but may not work. or check for any dry soldering. check the blue cap

Good luck.

yeah,
that is what I thought also

This appears to be a switch mode power supply, it's the only way that the transformer can be that small for the power output. In that case there is an awful lot that can go wrong on that PCB. Unless there is a visible problem, as Samath suggested, a cold soldered joint, or discolouration of the board or component, without a scope it may be difficult to track the problem down.
What is the running current of the DC motor. The starting current of a motor can be 5-10 times higher than the running current, since the motor looks more like a short circuit until the back emf sets itself up. Some switch mode supplies may struggle with the high initial peak current.
Cheers,
Richard