MIL-PRF-1/1314D
TABLE I. Testing and inspection - Continued.
1/
Airflow through the radiators required for cooling at sea level shall meet the following:
Anode dissipation ............................................................................................................... 500 W
Airflow................................................................................................................................. 17 cfm (min)
Static pressure.................................................................................................................... 0.90 Inch (H2O) (approximate)
Heater-cathode seals ......................................................................................................... 1.0 cfm (min)
Screen-grid control-grid seals............................................................................................. 1.0 cfm (min)
Incoming air temperature.................................................................................................... 45°C (max)
Radiator hub temperature (at fin adjacent to anode seal) .................................................. 250°C (max)
Tube temperature (at any point) ......................................................................................... 200°C (max)
Cooling shall be applied prior to and during application of any voltages and shall be maintained for 1 minute after the removal
of all voltages. Provision shall be made for unobstructed passage of cooling air between radiator fins and between the anode
terminal and adjacent radiator fin. The volume of cooling air indicated for various seals is only approximate. Distribution of
cooling air may vary with the cavity configuration about the tube. For most satisfactory operation, the maximum temperature
at any point on the tube shall be below 200°C.
2/
The cathode of the tube, because of transit time effects which raise the temperature of the cathode is subject to considerable
back bombardment in ultra-high frequency service. The amount of heating due to bombardment is a function of the operating
conditions and frequency, and must be compensated for by a reduction of the heater input to prevent over heating of the
cathode with resulting short life. For long life, tube type 6283 and 8500 should be put in operation with rated heater voltage.
After the circuit has been adjusted for proper tube operation, the heater voltage should be reduced to a value slightly above
that at which circuit performance is affected. In any case, it is important from a tube life standpoint to keep the filament
voltage at as low a level as possible consistent with required performance. However, the filament voltage should not be
reduced below 5.5 volts. At a frequency of 900 MHz and with typical operating conditions, the heater voltage can be reduced
to approximately 5.5 volts. At lower frequencies, the reduction will be less. Minor circuit readjustment may be necessary after
this adjustment. The procedure for determining proper heater power should be repeated periodically.
Applied voltage shall be approximately sinusoidal. The pulse duration 2 to 3.5 µs, prr = 60. Also, ec1 = ec2 = eb = 750 volts
3/
and tk = 90.
4/
Any frequency within the specified range may be used.
5/
This test shall be for screen grid to control-grid amplification factor and shall be calculated by dividing the difference in Ec2 (50
V) by the difference in Ec1 as read from the electrode voltage (1) (grid) and electrode voltage (2) (grid) tests.
6/
This test shall be calculated by dividing 50,000 by the difference in Ec1 as read from the electrode voltage (1) and the
electrode voltage (3) (grid) tests.
7/
This test is to be the first test performed at the conclusion of the holding period (t = 72 hours).
8/
With qualifying activity (DSCC-VQE, vqe.chief@dla.mil) approval both qualification and conformance inspection, part 3 life test
requirements for tube type 6283 may be satisfied using alternate life test conditions specified as follows:
F = 427.5 ± 22.5 MHz;
t = 500 hours min;
Ec2 = 1000 v;
po = 12.0 kw
(see 4/)
Ec1 = -50 V dc;
Pd = 2.2 kw
Ef = 6.3 V;
Du = 0.01
tp = 15 - 17 µs
Eb = 5000 V dc;
Manufacturers using the alternate life test requirements shall provide service-life guarantee (see 9/) with all tubes delivered
and tubes shall be marked accordingly. Life test end points specified shall apply to alternate life test qualification and
conformance inspection part 3 as well as to originally specified life-test qualification and inspection 3.
9/ Service-life guarantee (MIL-PRF-1): Type 6283 tubes manufactured using processes qualified and conformance inspected
(part 3) in accordance with alternate life test (see 8/) shall provide service-life guarantee with guaranteed service system-
deployed, accumulated tube operating time of 500 hours minimum. Type 6283 tubes sold under service-life guarantee shall
be marked with the following pertinent information: JAN-6283, manufactured date code and serial number.
10/ This specification sheet uses accept on zero defect sampling in accordance with MIL-PRF-1, table III.
11/ Output capacitance measured between anode and screen grid. Control grid connected directly to screen grid.
12/ Input capacitances measured between control grid (G1) and cathode. Control grid tied directly to screen grid (G2).
5
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