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New home-brew 40 meter RF deck

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March 23, 2018, 08:17:57 PM *
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Author Topic: New home-brew 40 meter RF deck  (Read 3093 times)
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« Reply #75 on: February 27, 2018, 06:14:08 PM »

BTW, a dummy something I learned the hard way:  Never suck air from the top down thru the tube bottom and out. I once had a blower on the outside of the house that pulled air out. It was a big (and expensive) external anus 3CX tube. It was quiet and efficient. But the tube failed quickly because the hot air thru the plate pushed hot air onto the filament seals and the fil seals failed. Always push air in from the bottom thru the top as most smart people do.. :-)


Expensive lesson indeed! I have an 833A that shows open filament and it was a NOS from the signal corps. There are no solder connections in these tubes. Everything is spot welded. The filaments in an 833 are in parallel and it is possible to have a tube that only lights up on one side. You can usually tell if one side is open as the filament tension springs will be fully extended. In fact that's a test or sign to look for if your window shopping online. Well anyway, this 833 has perfect spring tension and I figure iI hook a model A buzzer ignition coil to the filaments and the other side to the plate, I may be able to see where it is arcing? Now how to fix it? I thought about trying to discharge a high voltage capacitor across the filament contacts to see if that would spot weld it together?  Sorry Ron, not trying to steal your show Grin Grin

The secrecy of my job prevents me from knowing what I am doing.
Patrick J. / KD5OEI
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« Reply #76 on: February 27, 2018, 11:16:49 PM »

I hope you can fix those tubes Ron. Rare types!

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