Technics SL-d30 Ground Wire Installation
After building an amp for our house record player, you could only play-back record with an annoyingly loud hum; a grounding problem, in that it wasn't grounded from the player to the amp.
A quick search online found someone else who'd had the exact same problem;
https://audio44.wordpress.com/2014/03/10/ground-wire-for-technics-turntable/
It was also a good time to clean out some of the 30 year old dust that had accumulated.
Electronics DIY stuff