View Single Post
Old 5th Jan 2021, 9:13 pm   #35
em536716
Hexode
 
em536716's Avatar
 
Join Date: Dec 2017
Location: South East London
Posts: 301
Default Re: My newly found Marconi 707

Quote:
Originally Posted by Panrock View Post
Quote:
Originally Posted by em536716 View Post
The spot is quite bright!
In a word, "Wow"! No sign yet of an ion burn, at least from the photo.

Before signing off the tube as definitely good, it might be worth checking for grid-cathode and heater-cathode leaks. I suggest using an Avo or similar on the high resistance range and test 'cold', with the tube unplugged from its base. The situation can unfortunately change when 'hot' but I would tend not to run this tube without proper operating voltages and scans because the (pristine?) phosphor could so easily be damaged. Just my opinion.

Steve
I do have an old AVO somewhere. I was speaking to a fellow restorer who mentioned this to me.

I’m aware of the presentable damage to the phosphor, was just a quick test I wanted to carry out. Saw a lot of good discussion on testing, actually, I under powered the EHT with 1KV just in case I did manage to ruin the face of the tube. I was surprised to see it was that bright in all honesty! The tube will go in a box locked away until it’s testing time. Last thing I want to do is get carried away with it!
em536716 is offline