If the circuit draws 20 mA, you’ll want a higher rated fuse. Probably something like 100 mA. Might wait until everything is laid out and measure actual current draw before deciding on a fuse. Be careful testing low current fuses with a multimeter. The meter may produce enough current to blow them unless you use a series resistor.
I won’t comment on other components without seeing a schematic and might not then.
Mike
please check suggested schematic.
I could add the fuse later, probably best suited after the rectifier.
the main ac input feeds the bridge rectifier, then with resistor voltage divider it delivers 9-22v dc to LDO. LDO easily delivers 3.3v and with limiting resistor it ensures small current to the SSR which has 1.2v drop at the internal LED. Then it delivers the AC_L power line to the target circuit while AC_R line is connected to it directly.
this is what I have suggested.
these panasonic relays are interchangeable so that if one is not available at lcsc i can get another one from digikey or so. the smallest one of 300 mA is enough since PS1 is rated at 10W (or 17W in some extreme cases). this makes 100v AC at 17W requires 170 mA, most cases will be a lot less than this.
I wished for slightly cheaper solution but can't figure it out now.
You can use something like that https://www.boospa.net/en/tbs106a-pneumatic-switch.html for your main power switch.
please check the image attached.
the image is the power supply i want to create a substitute for. it has to have the showed button in that exact place and exact form in order to fit and work properly.
I could not find such buttons to be rated for higher voltage till now, except in LCSC which I don't know if I can trust it xD... but this one for example can work in the activation circuit since it won't need much current:
https://www.lcsc.com/product-detail/Push-Switches_XKB-Connection-XKB8080-Z_C318860.htmlthe original thought was to get one which can directly switch the ac power, that one requires say 200mA in the same formfactor as seen in picture below. i could not find one.
and my requirement is to have the entire circuit totally powered off when the button is not pressed... so i can't for example have the bridge rectifier + LDO before the switch in order to use low voltage switch. this way they will be active all the time.