MIL-PRF-1/1733A(NAVY)
TABLE I. Testing and inspection - Continued.
11/
This requirement shall be waived for manufacturers qualified to tube type 8932 (see 28/).
12/
Water system requirements. In order to minimize maintenance, it is recommended that the water cooling system be of the closed
type, utilizing water of acceptable quality as specified herein, to prevent excessive deposition, corrosion, and electrolysis.
Deposition of material not only restricts water flow, but also prevents proper transfer of heat from the tube elements to the cooling
water. Corrosion and electrolysis may destroy the tube elements, ducts, and fittings. Cooling water of acceptable quality shall
have a specific resistivity in excess of 1 megohm-cm.
13/
The water flow to the anode cooling connection shall be 10 gpm. The water flow to the filament, filament cathode, grid(1) and
grid(2) cooling connections, shall be 0.8 gpm. Pressure drops are measured at the tube terminals.
14/
The tube shall operate continuously under the specified test conditions.
15/
The grid(1) voltage (Ec1) is adjusted for class B operation. Class B operation is defined as a negative Ec1 voltage which is
between 20 percent and 12.5 percent of the ec2 voltage.
16/
Circuit adjustments are permissible. The rectified RF output pulse length (tp) and the pulse repetition rate (prr) shall be as
specified herein. Peak output power is calculated by dividing the average output power by the duty factor. Duty factor is defined
as the product of pulse duration and the repetition rate. The average output power is measured by a calorimetric method using a
dummy water load, RCA Model MI 19198-A, or equivalent. Minimum output circuit bandwidth as checked by cold probe
techniques shall be 12 MHz to the 3 dB points and 20 MHz to the 6 dB points.
17/
With the anode connected to the cathode and grid(2) connected to grid(1), apply a partial sinusoidal voltage of 200 v peak to the
grid(1). Emission current shall be read on an oscilloscope connected across a noninductive resistor in series with the grid(1)-
grid(2) cathode circuit or by means of a current transformer.
18/
The RF input power is measured using a calibrated directional coupler. This power is the difference between the incident and the
reflected power as sampled by the directional coupler. Coupler calibration is accomplished by the calorimetric method, RF
substitution method, or other approved methods. Power gain is calculated by dividing the RF output power by the RF input power.
The grid circuit shall be adjusted for lowest VSWR in the drive line. Specification readings cannot be taken unless reflected
power is less than 10 percent of the incident power.
With conditions as specified herein, grid(1) current (I1) shall be recorded after specified time. All voltages shall be removed
19/
except filament voltage and grid(1) voltage, and then grid(1) leakage current (I2) shall be recorded. Calculate Ic from the formula:
Ic = I1 - I2.
20/
The following procedure (or equivalent) shall be used for measuring input and output resonant frequency.
a.
Set up equipment as in figure 2. Be sure tube is making good contact with cavity.
b.
Adjust the frequency of RF generator to obtain a resonant peak on the standing-wave indicator.
c.
The resonant frequency as read on frequency meter shall be within limits specified herein. (The input cavity and output
cavity shall be as shown on figures 3 and 4.)
21/
Each element not under test shall be tied to ground. Two tubes per month shall be tested. Failure of one or more tubes will require
100-percent testing. Two tubes per month may be resumed after testing of 20 consecutive tubes without failure.
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