This video explains how to adjust the offset and bias of transistor audio amplifiers and why you might want to perform these adjustments. To explain this, we go through the simplified schematic of a class AB amplifier.
00:00 Intro
00:25 Basic class B amplifier
02:22 Class AB amplifier
03:43 Thermal instability
05:02 Bias adjustment
06:18 Closed loop class B amplifier
07:20 Understanding the offset voltage
08:06 Offset adjustment
08:35 Identifying the trimpots on the PCB
09:42 How to adjust the bias
10:55 How to adjust the offset
12:19 Looking at crossover distorsion using the oscilloscope
13:53 Outro
How I built the dummy load used in this video:
https://www.youtube.com/watch?v=RCi1dMlmi9ASansui G-5700 service manual:
https://elektrotanya.com/sansui_g-5700_g-6700_g-7700_sm.pdf/download.html