UY235 plate characteristics measured with a curve tracer

This is a plot of the plate characteristics of the "super-control" screen grid amplifier tube, measured with a Tektronix 577-177 curve tracer (577 is the display unit, 177 is the standard semiconductors test fixture).

As can be seen, negative-resistance section is clearly visible, when the plate voltage is between 20 and 70 volts, however, less than the 90 volts of the screen-grid voltage. 

This negative-resistance portion of the plate characteristic is used to realize a dynatron oscillator (refer to RCA patent #2067366). 

Graph was annotated with the curve tracer controls settings, as follows:

 - control grid step voltage: 2V per step
 - Y-axis: 2 mA per division
 - X-axis: 20V per division

Two external power supplies have been used to deliver power to the screen grid (90V) and the heater (2,5V).

It very important to adjust the current limiter into the screen grid, as in some conditions during the sweep, and when plate voltage is disabled, it is easy to exceed the maximum permissible power dissipation.

The following image shows the test setup:

The following graph is the same UY-235 connected as a triode, having the screen grid connected to the plate.

 

 

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