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Re: 833A's plate color

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

Tesla list wrote:


Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

This says the plates should be an "orange-red" color:

http://www.adamhorden.co.uk/site_data/833a.pdf
Sounds like you are running a little too much power. But I do that too for a short time ;-)) I try to be very careful since bright orange is also the color of molten glass!
Maybe someone knows if running them bright orange will decrease their life to say 100 hours, or if it will decrease their life to 10 seconds?
High voltage isolated RF current measurements are nasty. Best just to judge by the color... 

Cheers,

        Terry


At 01:03 PM 3/21/2006, you wrote:
I am running an 833A based coil. The tube is NOS RCA from a now defunct AM radio station. I have approx. 3000 vac on the plates. I'm getting a nice 18 - inch brush discharge, but the plate color is bright orange. I have been told that I am pushing this tube. Is this correct? What should my plate /current/current be? How can this be measured? 

Thanks
I think you're OK for the kind of operation you're doing - you're never going to pile up hundreds of hours of operation. I think he's talking about the DC current, which can be measured at the low voltage / ground terminal of the transformer if desired. By the way, there is a standard method for measuring plate dissipation of big transmitting tubes. The temperature of the plate is measured with an optical pyrometer. Then the tube is operated with DC (no RF present) and the grid/plate voltages adjusted to give the same temperature. Under those conditions all of the power input is plate dissipation. Net tube efficiency can be determined by taking the difference between the DC plate current during operation and subtracting the plate dissipation from it. 

Ed