EZ12

The EZ12 is an indirectly heated full-wave rectifier with two plates and a common cathode for AC-mains power supplies. Telefunken and RFT show a centre-tapped secondary and input capacitor. Heater voltage is 6.3 V, but current differs: 0.85 A in Telefunken and 0.9 A in RFT. The eight-contact base has a central locating spigot; RFT cites the DIN 41509 socket. Dimension drawings describe different examples: Telefunken gives maximum diameter 37 mm and body height 93 mm, RFT maximum diameter 38 mm and overall height 112 mm. These measurements follow their respective drawings.

The sheets allow 100 mA DC at 2 × 500 V RMS secondary and 125 mA at 2 × 400 V or less. Between 400 and 500 V per secondary half, RFT requires 2 × Utr × I not to exceed 100,000 mW, using RMS volts and milliamperes; Telefunken prints the same relationship with a strictly-less-than sign. These are not guaranteed DC output voltages: Telefunken curves show output versus load and equivalent resistances of 300, 400 and 500 Ω, using a 16 µF capacitor. A curve of current in each plate versus applied voltage is also provided.

Maximum reservoir capacitance is 32 µF, minimum total series resistance 300 Ω and heater-to-cathode limit 550 V. Total resistance includes half-secondary resistance, primary resistance referred to the secondary and any added protective resistor; the minimum cannot therefore be compared only with measured secondary resistance. Restoration calls for checking these conditions together with load current and actual transformer voltage. An RFT edition dated June 1953 retains the designation; Telefunken sheets are catalogued as 1943. These are dates of consulted documents. Sources: Telefunken EZ12 sheet and curves; RFT, VEB Röhrenwerk Anna Seghers, EZ12, June 1953.