You might want to check the impedance of your Heathkit Cantenna. Early models did not have a coating on the resistive element and tend to change characteristics over time. I had one that doubled in resistance. Much more than that and you may be beyond the L7's ability to tune. 73, Bob AD3K From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Bill Dzurilla Sent: Wednesday, May 19, 2010 3:35 PM To: drakelist@zerobeat.net; w4...@aol.com Subject: Re: [Drakelist] Drake L-7 arc - plate capacitor issue? Now with video
Thanks, John. I noticed the black dot as well and it drove me crazy trying to figure it out. After many attempts to duplicate, it turned out to be the rotor on the Load cap. It disappears a moment before the arc because I was turning that control to the left at the time of the arc. That is what led me to believe, as explained by W8JI and others, that the arcing was being caused by inadequate loading. When I tried again and left the Load control on 5, there was no arcing. I had not noticed the difference between the 2 tubes until you mentioned it. Possibly just a result of the camera angle. If not, what could it mean? 73, Bill NZ5N --- On Wed, 5/19/10, w4...@aol.com <w4...@aol.com> wrote: From: w4...@aol.com <w4...@aol.com> Subject: Re: [Drakelist] Drake L-7 arc - plate capacitor issue? Now with video To: billdz....@yahoo.com, drakelist@zerobeat.net Date: Wednesday, May 19, 2010, 3:20 PM In a message dated 5/18/2010 10:38:27 P.M. Eastern Daylight Time, billdz....@yahoo.com writes: http://www.youtube.com/watch?v=iJRyNQnkEWA I notice 2 things: The tube nearest the transformer is displaying a red plate before the tube nearest the side panel and it appears to be more than the tube toward the panel side. I also notice what appears to be a small black dot near the first full turn of the plate coil. This is not on the ceramic as far as I can tell and is not one of the rivets holding the ceramic. It seems to disappear a split second before the arc is heard on the sound track. I don't have the cover off my L-7 so I can't duplicate what I am seeing bit that might be a clue to the problem. Good luck and please let us know what you find. 73, John, W4AWM
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