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MP573 Microphone preamplifier / Re: Output transistor bias issue?

« on: May 14, 2022, 05:05:17 PM »

Ok I dont know what happened but when I went through measuring all of those points, I found the bias voltage was down around 1v and was able to adjust it up to 3v.  So it seems to be fixed.  Perhaps I was measuring the wrong point the first time around.  
Thanks for your help.

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MP573 Microphone preamplifier / Output transistor bias issue?

« on: May 10, 2022, 03:59:13 PM »

Hi,

Just built a 573, all is working and the unit seems to sound good.

However, when I adjusted the bias of the output transistor, I couldnt get TP4 to go below 3.8v.  It started off around 5v, but wont adjust lower than 3.8v.
Is this a problem or within tolerance?