[R-390] 3TF7 Ballast Tubes

[Flowertime01 at wmconnect.com]

Roy,

You wrote that you had a ballast tube with a bright spot in it. Most of the 
3FT7 tubes also operate that way. some small portion or maybe two small 
segments glow and the rest of the filament is dark. We did worry when we did 
see a very short section glowing very bright. We though these tubes were about 
to burn out. I agree the voltage is off when you get a tube in this 
condition. Mostly we just considered we were looking for stable operation not exact 
value operation and as long as the R390 or R390A was not drifting or 
jumping around in frequency we let the tube go until it opened. 

For test gear, I think you went the right way. Your looking for better than 
just kind of close performance from the test gear. 

My emotions and my wallet are in violent churn over this problem. 

Roger AI4NI

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