{"product_id":"4cx20000a-8990-ceramic-metal-power-tetrode-tube","title":"4CX20000A \/ 8990","description":"\u003ch2 style=\"font-size: 32px; margin-top: 15px;\"\u003e4CX20000A tube specs\u003c\/h2\u003e\n\u003cp\u003eThe table below gives a general overview of the 4CX20000A so you can quickly confirm the main characteristics. For full operating limits, curves, cooling tables, and dimensional detail, use the data sheet download below.\u003c\/p\u003e\n\u003cp\u003e4CX20000A general specifications\u003c\/p\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; border: 2px solid #000;\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth style=\"border: 1px solid #000; padding: 10px; text-align: left;\"\u003eSpecification\u003c\/th\u003e\n\u003cth style=\"border: 1px solid #000; padding: 10px; text-align: left;\"\u003eDetails\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eTube type\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eCeramic\/metal power tetrode (4CX20,000A \/ 8990)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003ePlate dissipation (max)\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e20,000 W\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eScreen dissipation (max)\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e450 W\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eControl grid dissipation (max)\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e200 W\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eMaximum frequency for full ratings (CW)\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e110 MHz\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eAmplification factor (Mu)\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e6.7\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eFilament\/cathode type\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eThoriated tungsten mesh\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eFilament voltage\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e10.0 V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eFilament current\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e140 A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eInterelectrode capacitance (grounded cathode): input\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e190 pF\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eInterelectrode capacitance (grounded cathode): output\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e23.5 pF\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eInterelectrode capacitance (grounded cathode): feedthrough\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e1.5 pF\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eInterelectrode capacitance (grounded grid): input\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e83 pF\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eInterelectrode capacitance (grounded grid): output\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e24.5 pF\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eInterelectrode capacitance (grounded grid): feedthrough\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e0.2 pF\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eCooling method\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eForced air\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eBase type\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eCoaxial\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eSocket\/chimney note\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eConfirm against the installed hardware and data sheet before ordering; published references for this tube family include HF\/coaxial socket use and SK-320 \/ SK-326 air-system hardware references\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eOverall length\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e9.84 in (250 mm max)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eOverall diameter\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e8.80 in (22.4 cm)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eWeight\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003e14.0 lb (6.35 kg net)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eOperating position\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #000; padding: 10px;\"\u003eAxis vertical, base up or down\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3 style=\"font-size: 32px; margin-top: 15px;\"\u003e4CX20000A tube data sheet download\u003c\/h3\u003e\n\u003cp\u003eDownload the 4CX20000A data sheet to review detailed ratings, characteristic curves, airflow requirements, and dimensional information before purchase.\u003c\/p\u003e\n\u003ch3 style=\"font-size: 32px; margin-top: 15px;\"\u003e4CX20000A tube substitute \u0026amp; equivalent information\u003c\/h3\u003e\n\u003cp\u003eThe 4CX20000A is commonly identified with the 8990 designation, so that is the first cross-reference to check when replacing an installed tube. In practical buying terms, the most useful 4CX20000A tube equivalent is usually another 4CX20,000A \/ 8990 built to the same operating class and matched to the same mechanical and cooling setup. Published equivalent-product literature also describes this family as a direct replacement for U.S.-manufactured 4CX20,000A \/ 8990 tubes. :contentReference[oaicite:1]{index=1}\u003c\/p\u003e\n\u003cp\u003eFor replacement work, do not rely on the number alone. Confirm the marking on the tube being removed, then verify socket style, chimney or airflow path, mounting orientation, and the operating conditions in the transmitter or amplifier. That extra check matters because published references for this tube family do not all describe the accessory hardware the same way, even though they agree on the core electrical characteristics.\u003c\/p\u003e\n\u003cp\u003eThe Penta Laboratories 4CX20000A can be used as a direct replacement for a 4CX20000A \u003ca href=\"https:\/\/pentalabs.com\/collections\/eimac-replacement-parts\"\u003eEimac tube\u003c\/a\u003e where the installed tube designation and operating requirements align. Penta also offers related options for other applications, including \u003ca href=\"https:\/\/pentalabs.com\/collections\/hi-fi-audio-amplification\"\u003eHiFi tubes\u003c\/a\u003e, \u003ca href=\"https:\/\/pentalabs.com\/collections\/tetrodes\"\u003etetrode\u003c\/a\u003e products, and a broader \u003ca href=\"https:\/\/pentalabs.com\/collections\/ham-radio\"\u003eham radio tube\u003c\/a\u003e range.\u003c\/p\u003e\n\u003cp\u003eIf you want to validate fit before ordering, contact Penta Laboratories with the details from the tube being replaced and the equipment it is installed in. As an established \u003ca href=\"https:\/\/pentalabs.com\/\"\u003evacuum tubes producer\u003c\/a\u003e, Penta can help confirm whether the 4CX20000A replacement you are considering matches your application.\u003c\/p\u003e","brand":"My Store","offers":[{"title":"Default Title","offer_id":45638812205300,"sku":"","price":0.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0707\/6996\/7348\/files\/4CX20000.png?v=1721368142","url":"https:\/\/pentalabs.com\/products\/4cx20000a-8990-ceramic-metal-power-tetrode-tube","provider":"Penta Laboratories","version":"1.0","type":"link"}