Similar full-wave rectifier with 4V heater but uses side-contact base (external anode connections) — different base type
AZ11
Similar full-wave rectifier with 4V heater but uses Rimlock/side-contact base — different base type and higher voltage drop
AZ4
Electrically identical but uses P-base (4-pin) instead of Y8A — different socket, not pin-compatible
Electrical Specifications
Absolute Maximum
Anode Voltage (max)Max Transformer Voltage (per half-winding RMS)500V
Rectifier
Peak Inverse VoltagePeak Inverse Voltage1,414V
Voltage Drop (typical)Voltage Drop (estimated from curves at 100 mA)20V
Max C-input Filter CapacitorLadekondensator60µF
Notes
Maximum DC output current depends on transformer voltage: 120 mA at 2x500V, 150 mA at 2x400V, 200 mA at 2x300V. The product 2 x UTr(Veff) x Idc(mA) must not exceed 120000.
Voltage drop (Vdrop) is not explicitly stated in the Telefunken datasheet. The value of ~20V at 100 mA per anode is estimated from the Ia=f(Ua) characteristic curve. The AZ12 has significantly lower internal resistance than the AZ1/AZ11 (~40V drop at 75 mA).
The AZ12 was Telefunken's steel-envelope successor to the glass-envelope AZ1 series, sharing the same Y8A base as other German steel tubes of the late 1930s. It was widely used in German radio receivers from 1938 through the 1950s.
Radiomuseum.org lists EZ81, GZ32, and GZ34 as successor types (from 1956 onwards), but these use different bases (Noval/Octal) and are not drop-in replacements.