EM71

The EM71 is an electronic tuning indicator with fan-shaped fluorescent display. Lorenz’s documentation of 15 December 1953 calls it a magic fan and shows a shadow sector varying with control voltage. Photographs reveal a feature visible even unpowered: screen centre and electrode assembly are offset from the bulb axis. Indirect oxide-cathode heating requires 6.3 V, 0.3 A. The eight-contact Loctal-family base has a central guide; Lorenz calls it a continental keyed base. Brimar lists EM71 as a replacement type, separately from the noval EM85 on the same page.

Lorenz gives two points with 0.5 MΩ anode resistor and second grid at zero. Supply and target 250 V: control zero to −20 V, shadow angle 120° to zero, anode current 0.5 to 0.15 mA. At 200 V: zero to −14 V, 115° to zero, 0.4 to 0.1 mA. Zero-control target current is respectively 2.5 and 1.6 mA. Brimar confirms at 250 V the 0.5 MΩ resistor, 0.5 mA anode at maximum shadow, 2.5 mA target and −20 V for zero shadow. Sensitivity therefore belongs to the circuit and supply used.

Lorenz limits distinguish 300 V operating anode from 550 V cold; maximum anode dissipation 0.5 W. Target: maximum 250 V, minimum 150 V, cold 550 V; cathode maximum 6 mA, grid leak 3 MΩ, heater–cathode 100 V DC or AC RMS. Heater deviation ±10% from 6.3 V is allowed. Lorenz specifies the contact beside h1 for target supply and suggests securing the bulb dome with a movable socket. Drawing: maximum overall length 69 mm, bulb diameter 29 mm ±0.4 mm. Mounting and fan orientation are part of correct application.