range values for equipment design the eimac 4cx250b/m is a ceramic/metal, forced-air cooled external-anode tetrode with a maximum anode dissipation rating of 250 watts. the 4cx250b/m is intended for use in applica - tions where tight control of electrical specifca - tions is required and replaces the 4cx250b in all applications. this tube utilizes a ruggedized internal structure and utilizes a welded anode cap for improved reliability. radial beam power tetrode cpi | 4cw50,000j for information on this and other cpi products, visit our website at: www.cpii.com , or contact: cpi mpp, eimac operation, 607 hansen way, palo alto, ca 94303 telephone : 1(800) 414-8823. fax : (650) 592-9988 | email : powergrid@cpii.com july 2011 the values listed above represent specifed limits for the product and are subject to change. the data should be used for basic information only. formal, controlled specifcations may be obtained from cpi for use in equipment design. ch aracteristics 1 electrical cathode: oxide coated, unipotential filament voltage 6.0 0.3 v current at 6.0 volts 2.6 a direct interelectrode capacitances (grounded cathode) 2 cin 15.7 pf cout 4.5 pf cgp 0.04 pf amplifcation factor, average (screen-grid) 5 frequency of maximum ratings (cw) 500 mhz mechanical: overall dimensions: length 2.46 in; 62.5 mm diameter 1.64 in; 41.7 mm weight (approx.) 4 oz; 113 gm operating postition any maximum operating temperature: ceramic/metal seals & envelope 250 c anode core 250 c cooling forced air base special, 9-pin jedec-b8-236 recommended air system socket sk-600 series recommended air chimney sk-606 4cx250b/m 1 characteristics and operating values are based upon performance tests. these fgures may change without notice as the result of additional data or product refnement. cpi mpp, eimac operation should be consulted before using this information for fnal equipment design. 2 capacitance values are for a cold tube as measured in a special shielded fxture in accordance with electronic industries association standard rs-191. min. nom. max. filament current @ 6.0 volts 2.3 -- 2.9 amperes cathode warm-up time 30 60 -- seconds interelectrode capacitance 1 (grounded cathode circuit) cin 14.2 -- 17.2 pf cout 4.0 -- 5.0 pf cgp -- -- 0.06 pf interelectrode capacitance 1 (grounded grid circuit) cin -- 13.0 -- pf cout 4.0 -- 5.0 pf cpk -- 0.01 -- pf 1 capacitance values are for a cold tube as measured in a shielded fxture in accordance with electronic industries assocation standard rs-191. 1 cpi | radial beam power tetrode 4cx250b/m / 7203a 7203a
absolute maximum ratings: anode voltage 2000 vdc screen voltage 300 vdc anode current 0.250 adc plate dissipation 250 watts screen dissipation 12 watts grid dissipation 2 watts heater-to-grid voltage 150 volts note: typical operation data are obtained from direct measurement or by calculation from published characteristic curves. adjustment of the rf grid voltage (feedback) to obtain the specifed anode current at the specifed bias and anode voltages is assumed. if this procedure is followed, there will be little variation in output power when the tube is changed. radio frequency amplifier class c, cw operation typical operation measured values, grid-driven anode voltage 500 1000 1500 2000 vdc screen voltage 250 250 250 250 vdc grid voltage -90 -90 -90 -90 vdc anode current 250 250 250 250 madc screen current 45 38 21 19 madc grid current 1 35 31 28 26 madc driving power 2 4.0 3.5 3.2 2.9 watts useful output 3,4 70 190 280 390 watts 1 approximate values 2 approximate, measured in vhf service 3 approximate, delivered to the load 4 for measured case; may vary from tube to tube cpi | radial beam power tetrode 4cx250b/m / 7203a 2 radial beam power tetrode 4cx250b/m application mec h anical mounting - the 4cx250b/m may be mounted in any position. socketing - the eimac sk-600 series air system sockets or a socket having equivalent characteristics is required. sockets are available with or without built-in screen capacitors and may be obtained with either grounded or ungrounded cathode terminals. cooling C suffcient forced-air cooling must be provided for the anode, base seals, and body seals to maintain operating tem - peratures below the rated maximum values. air requirements to maintain anode core temperatures at 200 c with an inlet air tem - perature of 50 c are tabulated below. these requirements apply when a socket of the eimac sk-600 series and an eimac sk-606 chimney are used with an air fow in the base-to-anode direction. tube life is prolonged if the anode temperature is maintained at values lower than the maximum rating. the blower selected in a given application must be capable of supplying the desired airfow at a back pressure equal to the pressure drop shown in the chart plus any drop encountered in ducts and flters. the blower must be designed to deliver neces - sary airfow at the desired altitude. sea level 10,000 feet anode dissipation air flow pressure air flow pressure (watts) (cfm) drop (cfm) drop (in. of water) (in. of water) 200 5.0 0.52 7.3 0.76 250 6.4 0.82 9.3 1.20 at 500 mhz or below base cooling air requirements are satisfed automatically when the tube is used in an eimac air-system socket and the recommended air fow rates are used. experience has shown that if reliable long life operation is to be obtained, the cooling air fow must be maintained during standby periods when only the heater voltage is applied to the tube. the anode cooler should be inspected periodically and cleaned when necessary to remove any dirt which might interfere with effective cooling. vibration C the 4cx250b/m is capable of withstanding shock and vibration, such as encountered in shipment and normal han - dling. the tubes will function well in environments where shock and vibration are anticipated. 7203a
electrical heater operation - the rated heater voltage for the 4cx250b/m, 6.0 volts as measured at the socket, should be maintained at this value to obtain optimum performance and maximum tube life. in no case should the voltage be allowed to deviate from 6.0 volts by more than plus or minus fve percent (5%). short-time changes of +/- 10% will not damage the tube, but variations in performance must be expected. the heater voltage must be maintained within +/- 5% to minimize these variations and to obtain maximum tube life. at frequencies above approx. 300 mhz transit-time effects be - gin to infuence the cathode temperature. the amount of driving power diverted to heating the cathode by back-bombardment will depend upon frequency, anode current, and driving power. when the tube is driven to maximum input as a class-c ampli - fer, the heater voltage should be reduced according to the table below: frequency m h z h eater voltage 300 and lower 6.00 volts 301 to 400 5.76 volts 401 to 500 5.50 volts cathode operation - the oxide coated unipotential cathode must be protected against excessively high emission currents. the maximum rated dc input current is 200 ma for plate modu - lated operation and 250 ma for all other types of operation with the exception of pulsed applications. the cathode is connected internally to four pins and all four should be used to make connection to external circuits to low - er inductance. at radio frequencies it is important to keep the cathode leads short and direct and to use conductors with large areas to minimize the inductive reactances in series with the cathode leads. it is recommended that the rated nominal heater voltage be ap - plied for a minimum of 30 seconds before other operating volt - ages are applied. where the circuit design requires the cathode and heater to be operated at different potentials, the rated maximum heater-to-cathode voltage of 150 voltage should be observed, regardless of polarity. grid operation - the maximum rated dc grid bias voltage is -250 volts and the maximum grid dissipation rating is 2.0 watts. in ordinary audio and rf amplifers the grid dissipation usually will not approach the maximum rating. at operating frequen - cies above the 100 mhz region, driving power requirements for amplifers increase noticeably. at 500 mhz as much as 20 watts of driving power may have to be supplied. however, most of the driving power is absorbed in circuit losses other than grid dis - sipation, so that grid dissipation is only increased slightly. sat - isfactory 500 mhz operation of the tube in a stable amplifer is 3 radial beam power tetrode 4cx250b/m cpi | radial beam power tetrode 4cx250b/m / 7203a indicated by grid-current values below approx. 15 ma. the maximum permissible grid-circuit resistance per tube is 100k ohms. screen operation - the maximum rated dissipation for the screen grid is 12 watts and the screen input power must be kept below that level. the product of peak screen current and peak screen voltage approximates the screen input power when amplitude modulation is used. in some cases screen cur - rent may tend to be negative. the 4cx250b/m shows reduced screen current, compared to the 4cx250b, and is therefore preferred for use in amplifers where screen supply voltage regulation is poor or where an increase in screen current above the normal value will cause a signifcant reduction in voltage. at uhf increased output (cavity) loading is recommended to reduce screen current even if the overall tube effciency is re - duced somewhat. fault protection - all power tubes operate at voltages which can cause severe damage in the event of an internal arc, especially in those cases where large amounts of stored en - ergy or follow-on current are involved. some means of protec - tion is advised in all cases, and it is recommended that a series resistor be used in the anode circuit (20 to 50 ohms) to limit peak current and provide a means of dissipating the energy in the event of a tube or circuit arc. for an oxide-cathode tube such as the 4cx250b/m a maximum of 4 joules total energy may be permitted to be dumped into an internal arc. amounts in excess of this may permanently damage the cathode or the tube grids. additional information is found eimacs application bulletin #17 titled fault protection, available on request. rf radiation - avoid exposure to strong rf felds even at rela - tively low frequency. absorption of rf energy by human tissue is dependent on frequency. under 300 mhz most of the en - ergy will pass completely through the human body with little attenuation or heating affect. public health agencies are con - cerned with hazard even at these frequencies. osha (occu - pational safety and health administration) recommends that prolonged exposure to rf radiation should be limited to 10 mil - liwatts per square centimeter. interelectrode capacitance - the actual internal inter - electrode capacitance of a tube is infuenced by many variables in most applications, such as stray capacitance to the chassis, capacitance added by the socket used, stray capacitance be - tween tube terminals, and wiring effects. to control the actual capacitance values within the tube, as the key component involved, the industry and the military services use a standard test procedure as described in electronic industries associa - tion standard rs-191. this requires the use of specially con - structed test fxtures which effectively shield all external tube leads from each other and eliminates any capacitance reading to ground. the test is performed on a cold tube. other fac - tors being equal, controlling internal tube capacitance in this way normally assures good interchangeability of tubes over a 7203a
4 radial beam power tetrode 4cx250b/m cpi | radial beam power tetrode 4cx250b/m / 7203a period of time, even when the tube may be made by different manu-facturers. the capacitance values shown in the manu - facturers technical data, or test specifcations, normally are taken in accordance with standard rs-191. the equipment designer is therefore cautioned to make allow - ance for the actual capacitance values which will exist in any normal application. measurements should be taken with the socket and mounting which represent approximate fnal layout if capacitance values are highly signifcant in the design. hot surfaces - air-cooled surfaces and other parts of tubes can reach temperatures of several hundred degrees c and cause serious burns if touched for several minutes after all power is removed. high voltage - the 4cx250b/m operates at voltages which can be deadly, and the equipment must be designed properly and operating precautions must be followed. equipment must be designed so that no one can come in contact with high volt - ages. all equipment must include safety enclosures for high- voltage circuits and terminals, with interlock switches to open the primary circuits of the power supplies and to discharge high-voltage condensers whenever access doors are opened. interlock switches must not be bypassed or cheated to allow operation with access doors open. always remember that high voltage can kill. special applications - if it is desired to operate this tube un der conditions widely different from those given here, contact the application engineering dept., cpi mpp eimac operation, palo alto, calif. 94304 for information and recommendations. operating hazards proper use and safe operating practices with respect to power tubes are the responsibility of equipment manufacturers and users of such tubes. all persons who work with and are exposed to power tubes, or equipment that utilizes such tubes, must take precau - tions to protect themselves against possible serious bodily injury. do not be careless around such products. the operation of this tube may involve the following hazards, any one of which, in the absence of safe operating practices and pre - cautions, could result in serious harm to personnel. high voltage C normal operating voltages can be deadly. remember the high voltage can kill. low-voltage high-current circuits - personal jewelry, such as rings, should not be worn when working with flament contacts or connectors as a short circuit can produce very high current and melting, resulting in severe burns. rf radiation C exposure to strong rf felds should be avoided, even at relatively low frequencies. cardiac pacemakers may be affected. hot surfaces C surfaces of tubes can reach temperatures of several hundred c and cause serious burns if touched for several minutes after all power is removed. material compliance - this product and package conforms to the conditions and limitations specifed in 49cfr 173.424 for radioactive material, excepted package-instruments or articles, un2910. in addition, this product and package contains no beryllium oxide (beo). please review the detailed operating hazards sheet enclosed with each tube, or request a copy from cpi mpp, eimac opera - tion application engineering at 1-650-592-1221. 7203a
cpi | 4cw50,000j 5 radial beam power tetrode 4cx250b/m cpi | radial beam power tetrode 4cx250b/m / 7203a 7203a
6 radial beam power tetrode 4cx250b/m cpi | radial beam power tetrode 4cx250b/m / 7203a 7203a
7 radial beam power tetrode 4cx250b/m cpi | radial beam power tetrode 4cx250b/m / 7203a cpi 072011 7203a
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