- -. ~ ~ ~ X3500~~~~ 8321 4CX350A Er. ' VICCUiLOQUGt;H, N ic. 4CX350F RADIAL-BEAM POWER TETRODES The Elmac 8321/4CX350A and 8322/4CX350F are compact radial beam tetrodes with maximum plate dissipation of 350 watts and are intended for Class-AB, audic or rf amplifier service. These tubes are externally identical to the 4CX250B but contain rugged internal construction features. Amplification factor and cathode area have been increased over the 4CX250B to give higher transconductance and figure or merit. The 8321/4CX350A and 8322/4CX350F differ only in heater voltage and current; the 8321/4CX350A is used at 6.0 volts while the 8322/4CX350F its rated at 26.5 volts. Both types are of ceramic and metal construction and are recommended for new equipment design. ELECTRICAL GENERAL CHARACTERISTICS Cathode: Oxide-Coated, Unipotential Min Nom. Max. Heating Time - ------ 30 60 secs Cathode-to-Heater Potential --- -±150 - fl volts Heater: 4CX350A Voltage - ------- 6.0 volta 4CX350A Current - ----- 2.9 3.6 amps 4CX3SOF Voltage - ------- 26.5 volts 4CX350F Current -0.66 0.81 amps Amplification Factor (Grid-to-Screen)--13 Mmn. Nom. Max. Transconductance ( 1 b -150 ma)-''''''--------22,000 umhos Direct Iriterelectrode Capacitances, Groumnded Cathode: Input -22.2 26.2 uuf Output -5.0 6.0 uuf Feedback-05 uu Direct Interelectrode Capacitances, Grounded Grid and Screen: Input -------,, 17.9 21.9 uuf Output -5.0 6.0 uuf Feedback-01 uu Frequency for Maximum Ratings -- 500 MECHANICAL Base-~~~~~~~~~~~~~~~~~~~~Special 9-pin Maximum Operating Tremperatures: Ceramic-to-Metal Seals-20C Anode Core-20 Recommended Socket-~~~~~~~~~~~Eimac SK-600 Series Operating Pomition-n Maximum Dimensions: Height - 2.464 inch Seated Height-1.910 inch Diameter-~~~~~~~~~~~~~~~1.640 inch Cooling Forced air Net Weight-4 ounces Shipping Weight (approximate)-1.6 pounds (Effective 10-12.62) Copyrlght 1962 hy EitoI-McCullougli, Inc.
-- ~ 4CX350A/4CX350F AUDIO-FREQUENCY OR MODULATOR AMPLIFIER CssA 1 TYPICAL OPERATION (Sinusoidal wave, two tubes unless noted) MAXIMUM RATINGS (Per tube) DC PLATE VOLTAGE -2000 MAX. VOLTS DC Plate Voltage- -1000 1500 2000 volts DC SCREEN VOLTAGE - 400 MAX. VOLTS DC Screen Voltage -- - - 400 400 400 volts DC PLATE CURRENT - 300 MAX. MA DC Grid Voltag~e 1 - - - -- 24-24 -24 volts PLATE DISSIPATION - 350 MAX. WATTS Zero-Signal DC Plate Current 200 200 200 ma SCREEN DISSIPATION - 8 MAX. WATTS Max-Signal DC Plate Current 520 530 540 m GRID CURRENT - - - 2 MAX. MA Max-Signal DC Screen Current - - Effective Load, Plate to Plate - -10-10 ma - -- 2600 5000 7500 ohms * Approximate values Peak AF Grid Input Voltage (per tube) 8 21 21 21 volts 1Adjust grdba ooti ltdrr-il Driving Power-0 0 0 watts gri obainlised bis t erosigal Max-Signal Plate Input Power - -- 560 800 1080 watts plate current. Max-Signal Plate Output Power - - 190 400 600 watts RADIO-FREQUENCY LINEAR AMPLIFIER Class-AB 1 (Single-Sideband Suppressed-Carrier Operation) TYPICAL OPERATION (Frequencies up to 175 Mc, peak-envelope conditions except where noted) MAXIMUM RATINGS VOLTAG - 200 MAX.VOLTSDC Plate Voltage - ---- 1090 1500 2000 volta DC PLATE ~~~~DC Screen Voltage -400 400 400 volts DC SCREEN VOLTAGE - 400 MAX. VOLTS DC Grid Voltage 1- - - -24-24 -24 volts DC PLATE CURRENT - 300 MAX. WATTS Zero-Signal DC Plate Current 100 100 100 PLATE DISSIPATION - 350 MAX. WATTS Peak RF Grid Voltage* - 21 21 21 volts SCREEN DISSIPATION - 8 MAX. WATTS DC Plate Current - - - - 260 265 2710 ma GRID CURRENT - - - 2 MAX. MA DC Screen Current, * -- 4 45 45 m Plate Input Power - ---- 260 400 540 watts * Approximate values. Plate Output Power -9--- 5 200 300 watts 1Adjust grdba ooti itdzr-inl Two-Tone Average DC Plate Current 100 100 105 ma gri o otan bis lstd zrosigal Two-Tone Average DC Screen Current 8-7 -8-8 ma plate current. Resonant load Impedance - - - - 1300 2500 3750 ohms NOTE: "TYPICAL OPERATION" data are obtained by calculation from published characteristic curves. No allowance is made for circuit losses of any kind. Adjustment of the rf grid drive to obtain the specified plate current at the specified grid bias, screen voltage, and plate voltage is assumed. If this procedure is followed, there will be little variation in output power when tubes are changed, even though there may be some variations in grid and screen currents. The grid and screen currents which result when the desired plate current is obtained are incidental and vary from tube to tube. These current variations cause no difficulty so long as the circuit maintains the correct voltage in the presence of the variations in current. If grid bias is obtained principally by means of a grid resistor, the resistor must be adjustable to obtain the required bias voltage when the correct rf driving voltage is applied. APPLI CAT ION MECHANICAL MOUNTING - The 4CX350A and 4CX350F may be SK-600 or SK-elO socket is used with the SK-606 operated in any position. An Elinac Air-System chimney and air-flow in the base-to-anode direction. Socket, SK-800 series, or a socket having equivalent characteristics, is required. Sockets are available with or without built-in screen by-pass capacitors and At 500 mc or below, base-cooling air requirements may be obtained with either grounded or ungrounded are satisfied automatically when the tube is operated cathode terminals, in an Elmac Air-System Socket and the recommended air-flow rates are used. Experience has shown that if COOLING - Sufficient cooling must be provided for reliable long-life operation is to be obtained, the the anode, base seals and body seals to maintain cooling air flow must be maintained during standby operating temperatures below the rated maximum periods when only the heater voltage is applied to the values. Air requirements to maintain seal tempera- tube. The anode cooler should be inspected periodictures at 2250C in 50 0 C ambient air are tabulated on ally and cleaned when necessary to remove any dirt, page 3. These requirements apply when the Eirnac which might interfere with effective cooling.
The blower selected in a given application must be if cooling methods other than forced air are used, if capable of supplying the desired air flow at a back the recommended air-flow rates are not supplied or if pressure equal to the pressure drop shown below, there is any doubt that the cooling plus is adequate. any drop it encountered in ducts and filters. The should be borne in mind that operating temperature blower must be designed to deliver the air at the Is the sole criterion of cooling effectiveness. One desired altitude, method of measuring the surface temperatures is by the use of a temperature-sensitive lacquer. When MINIhMUM COOLING AIR-FLOW REQUIREMENTS temperature-sensitive materials are used, extremely SEA LEVEL 10,000 FEET thin applications must be used to avoid with interference the transfer of heat from the tube to the air Plate Ai-lw Pressure Pressure stream, which would cause inaccurate indications. DisiatonDrp inhe AirFlo rp Ice VIBRATION - These tubes are capable of satisfact- (Wrttr) ~~of water) of water) onily withstanding ordinary shock and vibration, such 250 5.s 0.6 7.7 0.85 as encountered in shipment and normal handling. 300 The 6.5 0.9 9.5 1.25 tubes will function well in automobile and truck mobile 350 7.81.2 1.2 1.9 ~~~~installations and similar environments. ELECT RI CAL HEATER - The rated heater voltages for the 4CX350A When signal voltages appear between screen and cathand 4CX350F are 8.0 volts and 26.5 volts respective- ode, as in the case of screen-modulated amplifiers or ly and these voltages should be maintained as closely cathode-driven tetrode amplifiers, the peak screenas practicable. Short-time variations of the voltage of to-cathode voltage is the sum of the d-c screen voltage ± 10% of the rated value will not damage the tube, but and the peak ac or rf signal voltage applied to variations in performance must be expected. The screen or cathode. heater voltage should be maintained within ±5%~ of its rated value to minimize variations in performance Protection for the screen can be provided by an overand to obtain maximum tube life, current relay and by interlocking the screen supply so that the plate voltage must be applied before screen CATHODE OPERATION - The cathode is internally voltage can be applied. connected to the four even-numbered base pins, and all four of the corresponding socket terminals should The screen current may reverse under certain conbe used to make connection to the external circuits. ditions, and produce negative current indications on the At radio frequencies it is important to keep the cathode screen milliameter. This is a normal characteristic leads short and direct and to use conductors with of most tetrodes. The screen power supply should be large areas to minimize the inductive reactances in designed with this characteristic in mind, so that the series with the cathode leads, correct operating voltage will be maintained on the screen It is recommended under all conditions. that rated heater A current voltage path be from applied screen to cathode must be provided by a bleeder refor a minimum of 30 seconds before other operating sistor or shunt regulator connected between screen voltages are applied. Where the circuit design requires and cathode and arranged to pass approximately 15 the cathode and heater to be operated at different milliamperes per connected screen. An electron tube potentials, the rated maximum heater-to-cathode series regulator can be used only when an adequate voltage is 150 volta regardless of polarity, bleeder resistor is provided. CONTROL-GRID OPERATION - The grid dissipation rating of the 4CX350A and 4CX350F is zero watt. The PLATE OPERATION - The maximum rated platedesign features which make the tubes capableof maxi- dissipation power is 350 watts. The maximum dissimum power operation without driving the grid into the pation rating may be exceeded for brief periods during positive region also make it necessary to avoid posi- circuit adjustment without damage to the tube. tive grid operation. The grid current rating of 2.0 At frequencies up to approximately 30 megacycles the milliamperes allows the flow of positive grid current top cap on the anode cooler may be used for a plate for peak-signal monitoring purposes. terminal. At higher frequencies a circular clamp or spring-finger collect encircling the cylindrical outer SCREENGRID OERATIO - Themaximu rated surface of the anode cooler should be used. power dissipation for the screen grid is 8 watts, and the screen input power should be kept below that MUTPEORAIN- ubsoeaignarlevel. The product of the peak screen voltage and the Idl or push-pull must share the load equally. It is indicated dc screen current approximates the screen input power except when the screen current indication good engineering practice to provide for individual is near zero or negative. metering and individual adjustment of the bias or screen voltage to equalize the inputs. in the usual tetrode amplifier, where no signal voltage Wher~e overload protection is provided, it should be appears between cathode and screen, the peak screen capable of protecting the surviving tube/s in the event voltage is equal to the dc screen voltage, that one tube should fail.
UHF OPERATION - The 4CX350A and 4CX350F are Some of the added circuit loss observed in UHF operauseful in the UHF region. UHF operation should be tion is in the base insulator of the tube. It is someconducted with heavy plate loading, minimum bias times necessary to use more than the recommended and the lowest driving power consistent with satis- minimum air-flow rates to maintain safe operating factory performance. It is often preferable to operate base temperatures at UHF. at a sacrifice in efficiency to obtain increased tube life. These tubes may be used in frequency multiplier At frequencies above approximately 300 mega- applications. Such operation results in low plate cycles, transit-time effects begin to influence the efficiency and requires high driving voltages. If the cathode temperature. The amount of driving power frequency multiplier is used as an output power stage, diverted to heating the cathode by back-bombardment it is preferable to operate the final tube as a freqwill depend upon frequency, plate current, and driving uency doubler rather than a frequency tripler. power. When the tube is driven to maximum input, the heater voltage should be reduced according to the table below: Frequency, Mc 4CX350A 4CX350F SPECIAL APPLICATIONS - these tubes under conditions If It is desired widely to different operate 300 and from lower 6.00 volts 26.5 volts those given here, write to Application Engineering 301 to 400 5.75 volts 25.5 volts Department, Eltel-McCullough, Inc., San Carlos, Cal- 401 to 500 5.50 volts 24.3 volts ifornia for information and recommendations. PIN NO. I. SCREEN GRID I*IOY * YCI DIMUNUIONAL OAl~h PIN NO. 2. CATHODE *. i. MAX, NOM. PINY NO.'. HEATER Ar 2~~:.3Z4 246 PIN( Nu.4. CATHODE 6 1.610 1.640 PIN NO.5. I.C. DO NOT USE FOR C 1.810 1.910' EXTERNAL CONNECTION0.70 80 PINr NOr.6. E 7110 CA;THODE.730.0 PIN NO.?7. HEATER G 18 PINJ NO.8. CATHODE HyAE b-b.ijedec DESIGNA\TIONI CENTER PIN- :untrol. GRID j.s K.2401.260 K~~ _ ~ _ ~~~~ (ni~i~d n_.~_ ANODE SONEEN GRID (CONTACT OUTER I CILINDIIIC*) F qo~~ ~ L DIMENSION5J IN INCHES a~~~~~~~ CONTACT SURFACE
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