Hey everyone,

Another forum newbie, another question... :)

I hope you're all well. I have, ostensibly, a L3 Unfilmed WP tube in a D760 purchased from TNVC. I am unable to take the scope apart to confirm that's the tube, but I can at least see a shielded/metal boot peeking out. I'll try to disassemble it.

The problem:

The problem I have is that in low light situations - which can include normal use on a cloudless night - I can see 'arcs' on the right side of the tube when the tube's gain is dialled to max.

What's interesting though is that if I look through the scope in high-light situations, i.e. outside near some streetlights, the arcing doesn't occur much if at all. It's only once the tube light level drops that I start to see the issue.

E: My apologies, I forgot to show you a video of this happening. https://streamable.com/lo929k

What I would like assistance with:

Ideally, I would like to know:

- Is this a "Do not pass go, do not collect $200" style of tube? Something that can only be repaired or resolved by a specialist, if at all. At least if it's an issue with the PSU and not the core.

- Is further degredation or damage likely? I was wondering whether I could use this in situations where I wouldn't expect to need filmless advantages. Certainly not ideal but it would be a good way to cope.

- Is the scope's objective F-stop (2) contributing to the arcing? I was thinking here that if I moved it to another housing, a US one with a better objective like a PVS14's F1.4, perhaps it wouldn't happen. I doubt it though.

Additional details:

I believe that this is a 3-plate tube, instead of a more traditional 11769 with EGAC. The gain potentiometer for the scope is wired up in such a way that leaves no room for an EGAC but I could be wrong.


For anyone reading this, I hope you enjoyed, and for anyone who can help - thanks for taking the time.