Hello everyone! I have a Cyrus one , issue 07, i had some caps replaced just as a hobby, then I was thinking to check and adjust the bias. I measured the stock one and had 24.1mV and 29.6mV after 15mins. (Nominal have to be 8-20mV) . I took out the r81 and R82 (130R) and replaced with 180 and 220R for a drop under 20mV. Now the amp it’s working, it seems that lost some low end but it is more precise. My problem is if i measure now across R107 i get 0,21-0,24mV on both cabanele, what have I done wrong?
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I put a trimmer pot today . With changed resistors it stays at 0,2mV , i put back the original resistors and the bias it’s rising slowly . What have I done wrong?
Hello,
I think there is a great mistake with the bias current in this amplifier. I have this amp and I made some tests. I don't know excactly the values that I messured but if You but Signal and load to it and after short time of heating then without Signal there is only perpaps 10 milliampere of biascurrent which shows that the powertransistors work in class B.
This is because the transistor of vbe multiplier is thermal direct coupled with the powertranies .
I think there is a great mistake with the bias current in this amplifier. I have this amp and I made some tests. I don't know excactly the values that I messured but if You but Signal and load to it and after short time of heating then without Signal there is only perpaps 10 milliampere of biascurrent which shows that the powertransistors work in class B.
This is because the transistor of vbe multiplier is thermal direct coupled with the powertranies .