I'm not a pedal builder, but I'm trying to fix my Rocktron The Hush noise gate.
Unfortunately applying contact cleaner and checking for bad connections did not solve the issue lol
it doesn't matter if I use it with a battery or power supply, or if it's by itself or connected with other pedals. this noise always happens when it's engaged, but it does go away if the threshold knob is at 1/4 or more.
also it generates white noise when activated.
Please check the video in the link to listen to this issue: https://www.reddit.com/r/guitarpedals/comments/lbb5p0/noise_gate_making_heartbeat_sound_when_engaged_why/