Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Eddy -
The cathode is "almost" grounded at the socket by a 470 pF cap, (a little feedback for linearization,) then through the 15 ohm cathode resistor to equalize the current between the tubes, and then RF Ground by a 0.005 uF cap. Then it's off through an RF choke for keying and cathode current monitoring, etc., essentially a 3.3 ohm resistor to DC ground. In the T-4(any), G3 is DC grounded at the socket, but in the TR-4(any), G3 is bypassed to the "bottom" of the 15 ohm cathode resistors.
Bottom line is, the 6GJ5 works just fine in the T/TR-4(any) with the same caveats as the 6JB6, i.e., not ALL brands work well. The same reliable brands, (Sylvania, Zenith, RCA and GE ALWAYS work,) Westinghouse, Raytheon, Standard and a few of the late term "rebranders" sometimes work. The tube was designed to work at ~16kHz, and only Sylvania actually characterized and published data for use in linear service at 2-30 MHz.
73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B & C-Line Service Supplement CDs <www.k4oah.com> EP Swynar wrote:
"EP Swynar" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Hi Again John, Interesting...! I can't honestly say that I've had the bottom cover off of my "...new/old" T4X here yet, but the schematic in the manual, at least, definitely shows that pin #8 (suppressor grid) of each tube is directly grounded, whilst pin #3 for each is connected to resistors, capacitors, etc., i.e. NO direct ground connection... This merits further investigation on the part of yours truly, Hi. ~73~ Eddy VE3CUI - VE3XZ
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