Tats a nice tube. I'm really starting to like nat a lot

Me too. Just discovered the other one is faulty and struggles to work.

Good news with the faulty one. I got it going on pulse starter and left it running overnight before the weekend. Now it starts as normal on Quickstart. There is a strange brownish band in from one end. Is that the contaminant precipitated out so it can do no more harm?

Yes that will be oxides and tungstates from air entering the tube and reacting with the hot tungsten filaments. The mark should gradually spread and thin over time until it becomes barely visible, but it can continue to out gas so make sure you run this tube at least once a week for a few months.

Thanks eclipsilamps. I'll put it on long-term use for a bit.