Said Jim:
> Max quoted a price of $15. for GI7Bs plus shipping, which is reasonable
but
> I'm not going to beat his door down. YMMV, etc. The anode cooler on
these
> tubes is not particularly effective for full-output 100% duty-cycle use,
> and it should be replaced for these applications, or the tube derated.
> Liquid cooling is a good option.
I agree, I agree, but still... I'm using 1 of these (GI7bT variant, same
cooler) beasties in my mostly HB 144MHz amp, which has been seeing a LOT of
100% duty cycle usage lately (WSJT), and other than having to watch the Ia
needle and occasionally adjust the tuning, it has been turning out 300W+ for
hours and hours (30s on, 30s off, I had the lid off a few days ago, and the
"hood ornament" had become even more attractive! being colored a nice
blue/violet shade along the edges and corners of the fins...
The tube still works fine though.
I also have to admit the it has indeed run away for me a couple of times:
almost no output, 450mA Ia, and glowing a vivid red in the dark! But again,
after cooling down, no apparent ill effects!
What it all boils down to: How to get hold of a more suitable anode cooler
thingie? For me liquid cooling is not an option, and I don't have loads of
burnt out tubes to take apart for experimenting with reuse of cooling
fins....
> the cooler. The coolers make a nice Christmas tree or hood ornament.
They
> will also fit nicely on a rettysnitch without further modification.
>
Vy 73 de OZ1PIF, Peter
********** OZ1PIF **************
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Peter Frenning
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Denmark
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