[ohohyodafarted]

AFter several weeks of preliminary preparation, I embarked on another phase of the 15GP22 project.

AFter doing some groundwork to find a skilled welder with the proper TIG welding equipment, I located Dave the welder. Dave has a very high tech and up to date shop with the latest in welding technology.

I brought Dave a Kovar ring from a broken 15G for him to practice on and the tig welds he made on the test ring looked wonderful.

So this Saturday I took a 15GP22 and a 21AXP22 To dave to be welded. We had previously tested these tubes with a Helium leak detector at the lab at MSU, and located leaks on the welded seam of both tubes, and marked their location. I had Dave re-weld these defective areas on both tubes. Then I drove from Milwaukee to EAst Lansing and John Yurkon re-tested the tubes for leaks again to see if Dave's welding cured the leaks.

I regret to report that of the 4 welds, that were performed, 3 of them still leaked when tested. Upon close examination under a microscope, we could see that there was some minor porisity and some irregularities in the welding. By comparison, the original RCA welds were done on an automated machine which produced very consistant welds. So it was to be expected that welding by hand would have some inconsistancy.

It is apparent that to cure the weld line leaks, it may take multiple trys, re-welding each leak, and then leak testing after each attempt, in order to seal the leaking welds.

Without a having a leak Helium leak detector to test and re-test at our immediate disposal, the sealing of the tubes is not going to move forward. It is far to inconvenient to drive 700 miles round trip to test welds, and besides, we don't want to out stay our Welcome at MSU.

However, it is encouraging to note that I had sealed the glass/kovar innterface of the 15G with the epoxy we had been testing, and it did indeed seal the glass to Kovar leaks, on the aforementioned 15G.

At this point we are pretty much at the end of the road for John and myself. We feel it's to much of a gamble to seal tubes and rebuild them, and then to just cross our fingers that we have sealed all the leaks. So until a Helium leak detector falls in our lap, rebuilding 15G's here in the US is on an indefinite hold.

Fortunately it seems that RACS in France will be able to take up where John and I have left off. Perhaps when the equipment from Hawkeye is installed and up and running at the ETF in Hilliard, we may be able to proceed with more attempts in rebuilding 15G's here in the U.S.

Bob and John