Found with components dating to no later than November 1960, it could be one of the earliest B-15N’s produced.
We’ve nicknamed it “Chassis 24” after the hand- numbered chassis.
More information is with the schematics below.
Photos from the bench as she undergoes some long overdue service.
The circuit remains the same but heavily drifted and failed components have been replaced. Most carbon comp resistors measured 25 to 50 percent over their marked values. Surprisingly, the red Astron capacitors were within tolerance reading only slightly high on the meter.