Capacitor is not fully charging to trigger SCR

[DDT]

There is a problem with this circuit. The original document specified 3V for power supply. However, the capacitor 13 is only charges to around 0.6v and then stops when I used 3V, and it doesn't trigger SCR 7. I tried 9v and it works sometimes with this voltage. When I disconnect the gate of SCR 7, it seems to be charging fully. I am using TICP106D SCR. In the original document the SCR was BRY55. Both are sensitive gate SCR as far as know, so they should be interchangeable. Both have max Igt 200uA. I don't understand why the current is leaking this much through the gate. Do you have any suggestion? Disregard the rest of the circuit as they have no effect on capacitor 13. I am making this on a breadboard. Thank you.

[Andy Watson]

Has this ever worked? The schematic looks wrong.
With only 3V available and 4M7 (R 12) there will less than 1µA available for the gate current. If SCR 7 did trigger it would not latch because of R 8 - this would limit the current to about 100µA - the SCR requires mA (usually tens of mA) to hold-on.

How is the other SCR triggered? Its gate voltage is limited to about 1/3 of the base-emitter voltage transistor 22.

[DDT]

Thank you Andy. I believe the current required for triggering the SCR is coming from capacitor 13 when it's fully charged. Then it goes through resistor 8 etc. This is the arming delay period for alarm. It actually works with 9V. Holding current for sensitive SCRs is low. The other SCR also works, it conducts when break wire 10 (or NC switch) is broken. While charging, lamp 18 is on then goes off when capacitor charged. Transistor 22 won't let capacitor charge by conducting to ground if beak wire 10 is faulty when the arming button 15 is opened, which also cut off lamp 18. This let you know that break wire is faulty,