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During 2009 I purchased from Surplus Sales WW II vintage Raytheon 2J21 and 725A magnetrons each functioned as I had hoped. During the Fall months of 2010 I decided that I wanted another couple of working 50KW X band type magnetrons that I could use in my experimental electromagnet test setup. I purchased WW II Western Electric vintage magnetrons; three 2J50s and two 725A's. Only one of the 2J50s worked the remaining magnetrons outgassed significantly during their unused shelf life ( i.e. they all effectively shorted the HV pulse transformer output). The non functional 2J50's problem was observed when a bluish pink gas glow was seen inside the glass structure . Although I could not easily view any gas glow with the remaining magnetrons; it was obvious to me that they had outgassed causing HV breakdown between the cathode and anode for even a few kilovolts.

During Fall 2010 I purchased four Raytheon 2J55 magnetrons from ebay. Three vintage types from one source were sold at a very good price; two of these were black and appeared to be WW II or close to that period with old Navy markings; they looked like they were not used very much. Both worked very well when pulsed at 12KV at 12 amps; I was very happy about these. The third was manufactured in Japan ( blue in color); when I first tested it out it would only operate when pulse at about 6 amps at approximately 12KV with RF output. However, if I tried to increase the peak voltage even slightly the magnetron would become unstable and shift to a very high impedance mode without any RF output. I tested it out a day later; it would only operate in the unstable high impedance mode without any RF output. My guess at this point is the cathode electron emission may be low or some outgassing ( getter is black) is preventing an ample electron cloud formation but not sufficient outgassing to short the cathode to the anode. From the the 2J55 performance curve I estimate that it could only operate up to about 22 KW instead of 50KW at 12KV at 12 amps. Update: Recently after using the above gas clean up technique for diagnostic; the tube indeed indicated that it had outgassed. However I was not able to restore it operational.

I purchased a very new looking unused 2J55 (also blue), packaged in a styrofoam container, from another source; it also test good operating at 12KV at 12 amps; its RF output and operation was almost identical to the black vintage types described above.

I wanted a couple of pulsed X band magnetrons similar to the 6229. I decided to purchace three marine 4KW magnetrons from one source at ebay at a very good price. Its operating impedance is about the same as the 2J42 but at a little less peak voltage. The 2J42 pulse modulator worked very well for three of these marine magnetrons.

The three previously used types are: E5371 , MG5388 , and E5372 ; all operated producing RF output with the PFN tester ; the operating impedance for the first two seemed to be about where it should be , the RF output seemed stable ; the last was very unstable.

During 2011 I have purchased several more of these type X band 50 KW magnetrons from Ebay; one 2J49, two 730s, a Litton V91511-007, and another 725. All operated OK without any gas cleanup procedures except for the 725 which appears to also be outgassed beyond help. It seems that I have had better luck with the Raytheon type above magnetrons dating from the WW II vintage than the Western Electric.

Update:

Back when I purchased the outgassed tubes; magnetron ageing attempts were made, ie procedures used for sparking problems, without success; it was obvious that that they had outgassed much further than that associated with sparking. More drastic ion pumping was attempted using HV power supplies set for drawing only a few milliamps without success. They were then shelved as gone; beyond hope. However recently about a year later after much more agressive ion pump gas clean up experimentation I was able to get the 2J50 that glowed pink and one of the 725s to operate close to their intended operation (12KV @ 12A). However I have not been, yet, able to completely restore those tubes. After several days of non use they do out gas some; when first warmed up magnetron sparking occurs even at lower operating voltages. However using magnetron ageing techniques the gas cleans up in a few minutes and the magnetron seems to operates OK up to about 10 amps. At 12 amps sparking occurs along with mode shifting which probably means that the electron cloud build up is being interfered by the residual gas. The remaining above magnetrons appear to be outgassed beyond help.

Several months ago I purchased an old used magnetron book from Amazon.com ( see my review MIT series " Microwave Magnetrons") which describes magnetron construction procedures used during the WW II production. Preparations and procedures for pulling a vacuum, outgassing, bake out , and sealing off the tube is described. Only one of the five WW II vintage Western Electric magnetrons I purchased ( four of which were unused and still in the box) functioned and it functions very well! I don't know if outgassing is typical for the WW II vintage Western Electric magnetrons after 60 plus years or not; it maybe due to fabrication procedures, described in the book, were being rushed due to the war effort.

up to those of relatively recent manufacture. I also have had good luck with the X band 4KW marine type magnetrons.

During the early part of 2011 I purchased both the 2J22 and 2J29 S-band magnetrons from E bay. It was discovered that that they had outgassed much further than that associated with sparking as in the above case; they too were shelved as gone; beyond hope. However recently after using the much more agressive ion pump gas clean up experimental techniques, I was able to get the2J22 almost fully operational; the remaining 2J27 appears to be outgassed beyond help

During Fall of 2010 I purchased a vintage Sulvania 4J52 magnetron from E bay. Apparently during its shelf life it had outgassed to the point of the gas glowed purple; as in the above case they too were shelved as gone; beyond hope. However recently after using the much more agressive ion pump gas clean up experimental techniques. I was able to get the 4J52 amazingly very functional.

Mid 2012 Up Date:

This magnetron tends to outgas when not in use within a few days of non use. It takes me quite awhile to get it to operate close to its operational; after repeated gas cleanup the procedure has become more difficult. The only use I have for it now is for demonstrating it in cold cathode operation; however its pulse width is shortened considerably.