[Amps] Rehabbing that dusty old

[Steve Thompson]

> Applying some high voltage through some sort of current limiting device. 
> But it's not simple. You need to apply at least twice the normal high 
> voltage of the amp, no RF drive, current limited through a fast high 
> voltage fuse, and then adjust bias to control the current... not very 
> practical.

A hipot tester shoud spot a gassy tube - you could ask around locally if 
anyone has one - or build one.
> 
> The original tubes were Eimac, and the guy had a set of new Eimac tubes 
> on hand. I put them in, checked the whole beast, replaced a charred 
> resistor, then test ran the amp a few hours, trying all bands. But after 
> a few months, the guy was back, and again one of the tubes was flashing 
> over as soon as about 500 watts were going into the antenna! He had no 
> more spares. The non-arcing tubes of the two sets were too different to 
> be used together. 

Out of interest, in what way were they too different? Did you get a 
chance to see if the problem tubes behaved the same in a different amp?

Steve