FNIRSI DMT-99 Digital Multimeter

Analyzing a faulty fast 120W GaN USB charger from Novoo with 2x USB-C and 1x USB-A ports. A diagnosis and a temporary fix. Explaining how it works. A lot of measurements and oscilloscope waveforms. A simplified reverse engineered schematic. An active PFC, a flyback power supply with a synchronous rectifier and synchronous buck regulators. Switching transformer autopsy. The DMT-99 multimeter: https://www.fnirsi.com/products/dmt-99?sca_ref=9216013.ntkg5GeG0R&utm_source=af&utm_medium=ref&utm_campaign=9216013 The FNB58 USB tester: https://www.fnirsi.com/products/fnb58?sca_ref=9216013.ntkg5GeG0R&utm_source=af&utm_medium=ref&utm_campaign=9216013 The HRM-10 internal resistance tester: https://www.fnirsi.com/products/hrm-10?sca_ref=9216013.ntkg5GeG0R&utm_source=af&utm_medium=ref&utm_campaign=9216013 The 2-channel 180MHz oscilloscope: https://www.fnirsi.com/products/dpox180h?sca_ref=9216013.ntkg5GeG0R&utm_source=af&utm_medium=ref&utm_campaign=9216013 My DIY test load: https://danyk.cz/zatez2_en.html My DIY in-circuit ring tester: https://danyk.cz/avr_ring2_en.html My component marking calculator: https://kiloohm.info My CATculator: https://ohmslaw.eu Please support my channel on Patreon: https://www.patreon.com/DiodeGoneWild Instagram: https://www.instagram.com/savage_danyk/