PCL200

The PCL200 combines a triode and a pentode in one ten-contact Dekal envelope. Telefunken presents it for video output stages and gated automatic gain control in television receivers; the Mazda-Belvu sheet calls it a video amplifier. The two distinct systems provide, within one envelope, an amplifying section and another able to deliver more current. The sheets do not, however, assign each section a single fixed task in every circuit: the receiver's schematic determines its use.

The heater is intended for a 300 mA series chain and operates at about 15.5 V. The Mazda-Belvu sheet refers readers to the ECL200 documentation for other characteristics, but the PCL200 heater rating remains the one specified here and must be checked before considering substitution. The two systems have separate cathodes and connections: in Telefunken's pinout the triode uses pins 1, 2 and 3 for plate, grid and cathode; the pentode uses pin 7 for its plate, 8 and 10 for its screen grid, 9 for its control grid and 4 for its cathode and suppressor grid. The heater is on pins 5 and 6. This layout prevents treating the tube as a generic common-cathode triode-pentode.

Telefunken's measurements portray the two sections without conflating them. At 200 V on its plate and −1.5 V on its grid, the triode has 8.5 mA plate current, an amplification factor of 55 and transconductance of 5.2 mA/V. The pentode, instead measured with 150 V on its plate, 220 V on its screen grid and −2.1 V on its control grid, has 40 mA plate current, 8 mA screen current and transconductance of 28 mA/V. These are separate measurement points; they do not by themselves state the actual voltages in a particular television receiver. The same sheet sets plate-dissipation limits of 1.7 W for the triode and 6 W for the pentode, with a 2.5 W maximum for the pentode screen grid.

A Telefunken mechanical note recommends, where necessary, preventing the tube from working loose in its socket: a simple but relevant detail in equipment exposed to heat and handling. The curves for both sections on the following pages help show how currents vary with voltage and bias, without turning one test point into a general rule. Documentary sources: Telefunken, PCL200 Triode/Pentode, tentative data May 1965, curves January 1966; Mazda-Belvu, PCL200 Triode Pentode, January 1968.