Схемы металлоискателей MD4U

Hello all and thank you for the wonderful job you're doing, i have built sniffer xr71 and it did not output any sound except for when i put a speaker in the coil plug and the trimpot inside the board in the bottom left seems to control just fine also another potentiometer in the front panel, what i did so far is replace the mc14538 with cd4538 and mc14066 with hcf4066 and hef4066، no apparent shorts or lines that are cut, juice is 6 x lithium and 6s bms and stepdown converter to 12v.
Any help debugging and fixing the machine will be much appreciated and have a good day
- attached pdfs of the version i've worked on.
​PS: I have copy pasted this exact post in other forums still waiting for help.