BA283 AM Biasing Trimpot Issue?

lesabb

Member
2014-12-30 11:43 pm
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 can’t 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

Luc
 

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