I recently acquired a set of these boards and have read that there are issues with them. It relates to the bias and output transistors. I made the check of the bias as was mentioned in a previous forum and I get nowhere near the mv mentioned.
You are supposed to measure between the output with no input on and the middle leg of any output transistor, and you should get around 22 mv ideally. I am getting 1.4 mv. The DC offset is 10.4 mv and the ac ripple is near zero.
I ran the scope on the boards, and they do not put out the watts stated, only about 80 watts @ 8 ohms and just under 170 @ 4 ohms. The sine wave is clean with no ripples I can see, as I am worried about HF oscillations on this board.
Anyone has any thoughts on this, I was advised to change the 1k resistor to 910 ohms to have an ideal bias of around 22 mv.
Thanks Cheers Wayne
You are supposed to measure between the output with no input on and the middle leg of any output transistor, and you should get around 22 mv ideally. I am getting 1.4 mv. The DC offset is 10.4 mv and the ac ripple is near zero.
I ran the scope on the boards, and they do not put out the watts stated, only about 80 watts @ 8 ohms and just under 170 @ 4 ohms. The sine wave is clean with no ripples I can see, as I am worried about HF oscillations on this board.
Anyone has any thoughts on this, I was advised to change the 1k resistor to 910 ohms to have an ideal bias of around 22 mv.
Thanks Cheers Wayne