'Soft' On/Off Power Switch

[flotulopex]

I do have difficulties to make this circuit switch-ON.

Problem description: if I switch-off my power-supply for about 2 to 3 minutes and switch it on back again, the soft-switch won't function and power the PIC. But once the PIC has been "successfully" powered, it works any time (as long as I don't switch-off the supply again).

For Q1, I implemented a 2N3906, then aBC307, then BC557; no way to make it work. Finally an old (metal case) 2n2905.

By "chance", I got it to work by making a false-contact between the 2n2905's (Collector is connected to case) and R1 (any pole) on the breadboard.

Once the contact has shortly happened and as long as the power-supply is not disconnected, the soft-switch will work perfectly (!?).

What shall I do to correct this?
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=2705&stc=1&d=121475975 5">
NB: I didn't implement D2 + R3 since the program shuts-off the circuit by program (RA1 = 0).