Chosen Solution
When powered on, the unit emits high pitched whooping sounds (see video). I opened it up, hoping to see something obvious, but everything seems fine for a 25yo device. It does this both on battery and on Wall plug. Suggestions? I don’t have access to an oscilloscope, just a soldering iron, multimeter and limited understanding.
@okeribok that does not sound like interference. It sounds like a bad power supply (MOSFET) or bad power amp. We’ll have to see the boards etc. to help you further. Attach some good pictures of your board to your question. Adding images to an existing question
