As the cap charges there will be current through the resistors thus base current. As the voltage of the cap increases the current through the resistors will decrease to zero. When the cap is fully charged there will be no base current. So this circuit will produce a pulse low at the drain until the base current goes away.
So yes you have some base drive as the cap charges.
Why not just turn on power to the sequencer before everything else.
I have a mental defect, adding parts to sequencers and interlocks adds more failure modes.
Oh yes !! That is exactly what it is supposed to do. Just hold the circuit in a forced-off state long enough for the rest of the circuit to complete its power up - set/reset cycle. I'm assuming that's what Jon originally asked for. I think (and I might have misunderstood) that the goal was to have the circuit otherwise fully functional, and just disable the "self test" feature. So, we only need (I'm supposing) about a second or so to allow the remainder of the circuit to do the self test, and then return to the off state, internally. Externally, nothing will happen because the transistor will prevent the relays from firing during the self test.
And, adding more parts definitely adds more failure modes, but what the heck
4 more components - what are the chances? And, we're not exactly controlling the space shuttle here
But, the point is well taken.
Regards,
Steve
