Some SB-200 issues

[Kenneth G. Gordon]

Might anyone have a source for the 500 pfd 2KV mica capacitor, C-27, that is 
used to increase the value of the loading capacitor in the SB-200 on 80 
meters?

Mine is open, and I have, so far, found no supplier for one.

Might a disk ceramic cap work in this service, or do those not work properly 
in RF service (get hot)?

On another matter, I was testing my small stock of 572Bs last night by 
installing them one at a time and loading for maximum output. 

Most of my Cetron's were pretty well worn out. One was capable of only 100 
watts (input). Another was good for 250 watts. One was good for 500 watts, 
one for 675 watts and one for 700 watts.

A Chinese-made one was good for 900 watts, and two NEW Chinese-made 
tubes were also good for around 900 watts each.

When I installed the two better Cetrons and loaded it up, about 60 seconds 
after installing them, the better Cetron flashed inside momentarily and now it 
looks like only 1/2 the filament is lit and it is considerably dimmer than the 
other one.

Output fell by about 300 watts too.

Rats!

So, I installed the pair of new Chinese tubes.

Does anyone know if it is possible to "rejuvenate" 572Bs? 

I used to rejuvenate thoriated-tungsten filamented power tubes like the 
304TL, but am not sure if the 572B has such a filament or not.

Ken Gordon W7EKB

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