[Heath] Gettering 572B's for a Heathkit SB-200

[Kenneth G. Gordon]

On 9 Aug 2015 at 20:03, George Collins wrote:

> 
> Hello Group,
> I have a few 572B´s that having been unused for unknown lengths of time,
> probably several years. It is possible to getter this tubes be for putting them
> into service in order to avoid arcing or flash over? Are there any other
> measures that can be taken with the 572B´s to avoid failures at startup? I
> plan to use these tubes in an SB-200 amp. The amp is working now, but the tubes
> are weak. The replacements I have are either New Old Stock or "good" used.
> Thanks and 73, George, KC1V

Hello, George:

As I understand it, what you should do is to apply filament voltage, only, to 
the tubes for at least 24 hours. Then apply DC to the plate, beginning with 
about 500 volts, then raising it in some increment, say 200 volts, over a 
period of "a couple of hours", until you get them to the full 2150 VDC or so, 
watching the plate current in the meantime. Don't let plate current rise to 
much above 100 watts of dissipation. 2 VDC grid voltage should keep the 
plate current to 90 mA or less.

Ken W7EKB



Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne