[Techman]

Yes, I know what you mean about the gettering on these old valves, that was the problem with the valve that I mentioned in a previous post in that it had a filament short to grid, but I couldn't actually see it through the glass. It's not just the getter silvering, it's also that dark deposit caused by the early process of coating the filament with a special cathode emitting substance - I forget the name of it now, think it began with a 'Z', someone will know. Shame about the valve, but at least you've now tried all the options.