yakusa wrote:
Here is a picture. The DC offset voltage can be measured by using voltmeter, one probe to the output point, and another probe to the ground. The signal ground and the power ground are the same. If there is a voltage, then adjust the trimmer to reduce the voltage. If the output DC is so low ( say below 5mv) then there is no need to adjust. For 'one by one' it really means connect the 0.22 ohm resistors one by one to ensure each LM3886 has the minimum offset before hook all three together.pin #3 is the output but when the 0.22 resistor is in place (again- one at a time) that should provide continuity all the way to the main output pad - which should be easier and safer to measure.
Remember, those adjustments are interactive between chips and may require readjusting as you work.
dear sir,
I just got the same pcb as yours, I am very beginner, I've tried as you picture, but I still do not understand how to adjust the dc offset, you say to disconnect the resistor 0.22ohm and then adjust the trimmer to reduce the voltage. And you say one probe to the output point, it's mean the probe touch to the output speakers ( + ), and another probe to the ground?? I've tried as you describe, but the lm3886 chip were getting hot.
Please help me, step by step, because i'm very blind for this, and sorry for my bad english, hope you can help my problem.
Thanks.