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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: Tube Cooking posted by Quest on January 30, 2006 at 08:48:28:
In thoriated tungsten filament the rejuvination will work if the thoria content at the suface is low. Time at temp will allow thoria to diffuse to the surface from the center of the wire. Usually normal filament voltage will work withiout any plate or grid voltage present. A small increase in filament voltage will speed things up. Don't go higher than 10% over normal.Operating the tube at reduced filament voltage will cause reduced emission for the same reason. If the filament is running cold the thoria does not diffuse up to the surface at the same rate as it is consumed. Eventually there is not enough thoria at the surface to support the required emission for the application.
Thoriated tungsten emitters are carburaized during tube manufacture. This is part of the process that yeild high emission. The carbon is consumed during use and eventually is depleted to the point that emission is too low for proper operation. This is not reversable without being able to connect the tube to a vacuum pump and re-carb the filament, which is what a tube rebuilder does in a cheap rebuild.
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Follow Ups
- Re: Tube Cooking - beermanpete@socal.rr.com 23:00:29 01/31/06 (0)
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