U22

The Mazda U22 is a half-wave vacuum rectifier for television cathode-ray-tube high-voltage supplies. The 1939 sheet presents it with the U21 and explains a deliberate feature of indirect heating: delayed high-voltage output lets television circuits start before the CRT receives its plate supply. The U22 heater requires 2 V and 2 A. Heater and cathode are internally joined at one end, which matters for circuit supply and insulation.

The documentation illustrates the starting sequence with a timebase supplied through a UD41 or similar tube: scan-stage tubes heat and receive high voltage first; the U22 then reaches operating temperature and supplies the CRT plate. The delay helps protect the cathode and prevents a stationary bright spot damaging the screen. Tables state that output at 35 seconds is about 15% of its final value, not that full voltage is reached in 35 seconds.

The October 1948 sheet explicitly supersedes Sheet 12/6. One rating set gives 5200 V RMS plate supply, 14,500 V peak inverse, 1 mA average plate current, 20 mA peak and at least 50 kΩ limiting resistance. A second column permits 5 mA average and 55 mA peak with 10,000 V maximum inverse and at least 30 kΩ; the highest figures from both columns must not be freely combined. Transformer-winding distributed resistance may supply the required resistance. The 1939 sheet instead gives 4500 V RMS and 12,500 V inverse, so the editions must remain distinct.

Typical 1948 conditions use a 0.1 µF reservoir capacitor and 0.25 mA DC load. At 4000 V RMS input, tabulated DC output is 5.45 kV; at 5150 V RMS it reaches 7 kV. Ripple is about 14 V RMS at 50 Hz. These figures describe that circuit and load, not maximum current available at any voltage. Plate-to-heater-plus-cathode capacitance is 2.2 pF. Comparison with U21 also shows that related function does not establish mechanical identity: the original document gives U21 a four-pin base and U22 a Mazda Octal base.

The 1948 sheet calls the base British Octal, code B04, viewed from below: pin 1 carries heater, cathode and shield, pin 8 the other heater end, and the top cap the plate. Pins 2, 4, 6 and 7 are omitted; 3 and 5 have no assigned function. Follow the Mazda drawing rather than automatically applying another Octal family's pinout. Maximum overall length is 96 mm, seated height 83 mm and base diameter 29.5 mm; net weight is about one ounce. The earlier sheet gives 28.5 mm as maximum U22 diameter without the same base qualification. Any mounting position is allowed.

Documentation consulted: Mazda U21 & U22 High Voltage Rectifiers, Ediswan Radio, Sheet 12/6, 1 May 1939; Mazda U22 High Voltage H.W. Rectifier, The Edison Swan Electric Company, Issue 1/2, October 1948.