Vox AC100 Mark 2, later 1965 - Emihus zener diodes
Some notes on the bias circuit of the AC100 mark 2, later 1965 through to 1968.
Detail from the circuit diagram for the AC100 mark 2.
As in the "100W Amplifier" of late summer 1965, the bias voltage was clamped by a pair of zener diodes - see this page. For the AC100 mark 2, JMI turned to "Emihus", a subsiduary of EMI based in Glenrothes. The "Hus" part of the name was the original owner - Hughes International (UK), part of the Hughes Aircraft Corporation.
The 20v diode across the width of the board was a "HS2200", the 15v diode across the two solder terminals a "HS2150".
Detail of AC100 serial number 1579.
Below, a detail from the "Emihus" specification sheet, the columns left to right being: part number; zener voltage; tolerance (in %); max. zener current (unspecified); dynamic resistance (in ohms); max. dissipation (in mW); type of connection (A1 = axial, flying leads).
Detail from the Emihus spec. sheet.