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BA283 AM Biasing Trimpot Issue?
BA283 AM Biasing Trimpot Issue?
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Old 29th February 2016, 02:34 PM   #1
lesabb is offline lesabb
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Join Date: Dec 2014
Default BA283 AM Biasing Trimpot Issue?

I am newbie and trying to build the pre-amp section of the Neve 1073. I decided to bread board the BA283AM ONLY as per the attached schematics. I think there is a problem but i canít seem to find it. The collector voltage on the 2N6248 is 20.6V. Shouldn't it be higher? When I turn the trimpot nothing happens. The Base voltage is ~10.6V and the E is at ~ 10V, which I think is OK but a bit higher than previously reported (~3V). Consequently, the C voltage of Q1 is at ~10.6V (much higher than the reported 3.6V). The transformer is connected to the 24V PSU and to the output of the BA283AM as per the schematics.Any troubleshooting ideas? Thanks

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Old 29th February 2016, 03:34 PM   #2
Cortez is offline Cortez  Hungary
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Join Date: Dec 2002
Location: Hungary
Try to simulate this cct. Then you will know how it works and then you can compare the reality to the values in the sim.
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