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Will a magnetron draw 480 Watts without radiating energy?

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chris_leyson:
^^^ SeanB and Gyro are correct. Magnetrons used in microwave ovens DO NOT use BeO anode coupler insulators, if they did it would be clearly stated in the magnetron data sheet and there would be a mandatory warning lable stuck on the anode box, but too many people are lazy and don't check data sheets. Besides there is no reason to cool the anode coupling electrode. The anode block has press fit cooling fins which remove a few hundred watts of heat by forced air cooling. Also you can't go by color. BeO used in RF power transistors or for anode cooling blocks that were at one time used for some of the larger 4CXxxx transmitter tunes, for example, is white. Anode couplers will sometimes arc to the cavity due to a miss match and then it's usually game over at that stage. Low heater emission or hot spots on cathodes caused by "back heating" of the cathode can cause a drop in RF output power. An incorrect operating current or magnetic field strength can cause a drop in output power as will a damaged coupling loop.
Eimac 8873 was designed for conduction cooling and uses SK-1920 BeO "thermal link". BeO Cooling blocks were also available for 4CX250, but can't find data sheet. Eimac Y-799 or Y-808 may be the conduction cooled versions of the 4CX250s.

Gyro:

--- Quote from: chris_leyson on August 30, 2020, 10:41:58 am ---...
Anode couplers will sometimes arc to the cavity due to a miss match and then it's usually game over at that stage.
...

--- End quote ---

Apparently not... Replacements freely available. 5pcs sounds a bit optimistic though! ;D

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=magnetron+cap&_sacat=0

Quite what state the internals of the Magnetron look like by that stage of coupler damage is another matter, but the Anode coupler is a push-fit cap that doesn't interfere with the thick copper vacuum sealing pinch underneath it (just visible in the photo).




P.S. The coupler on my melted Panasonic Magnetron was still in perfect condition.

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