Bounty Hunter Land Star Threshold

[SVEN1]

I picked up one of these older detectors in working condition. I don't have and cannot find a schematic for the Land Star.
There are 4 trimpots on the PCB, wondering if one is a threshold adjustment and if so which one?

[SVEN1]

Found 4 trimpots on the PCB after opening the detector up.

[kt315]

maybe Melbeta will give a light? her file.

[Carl-NC]

R53 is the only possibility I can see for a threshold adjust. "ARM" feeds the micro, which then drives the speaker.

[SVEN1]

Thank you!!