I'm just going to think out loud a little bit. How about a switch like this:
https://no.mouser.com/ProductDetail...MAyF9RBguZAyGKGYIat%2bCQnNZ8Ptq/2NdKqHxz1yw==
Thru one set of momentary contacts we run the AC line to the supplies, so when you push the switch they turn on, when you release it they would turn off, except we will wire a relay across the contacts.
https://www.mouser.com/ds/2/418/NG_DS_ORWH_series_relay_data_sheet_E_0411-124938.pdf
The relay turns on if the voltage is above 18 volts (your comparator idea) and keeps them on. If the voltage is not above 18 volts they will turn back off when you release the switch. To turn it off you press the switch in the opposite direction and it turns the relay off. I think we could power the comparators from the big supplies. Maybe we could light a red light if you press the button and both supplies don't come on and a green one if they do so there would be an indication of power on and of a fault.
https://no.mouser.com/ProductDetail...MAyF9RBguZAyGKGYIat%2bCQnNZ8Ptq/2NdKqHxz1yw==
Thru one set of momentary contacts we run the AC line to the supplies, so when you push the switch they turn on, when you release it they would turn off, except we will wire a relay across the contacts.
https://www.mouser.com/ds/2/418/NG_DS_ORWH_series_relay_data_sheet_E_0411-124938.pdf
The relay turns on if the voltage is above 18 volts (your comparator idea) and keeps them on. If the voltage is not above 18 volts they will turn back off when you release the switch. To turn it off you press the switch in the opposite direction and it turns the relay off. I think we could power the comparators from the big supplies. Maybe we could light a red light if you press the button and both supplies don't come on and a green one if they do so there would be an indication of power on and of a fault.