DuMont 304H oscillograph

[Tube Radio]

I have one that is fully restored except for a few resistors in the vertical amp. Anyways about three years ago while using the scope the 5ADP1 CRT in it lost all ability to focus properly. I then tried several 5ADP* series CRTs all with the same problem, yet a 5CP1 works properly. I thought it was the CRTs, but one still has the QC sticker on it. I also tried the CRTs in an unrestored 304H and got the same or similar problem. I am gonna try and switch out the intensity and focus controls of the restored 304H (originals burned out and had to replace with regular variable resistors) with those in the unrestored 304H and see if my problem goes away. I kind of have to fix the scope as I have put $$ in restoring it before the problem occurred. I cannot use the 5CP1 as it is not flat faced even though that's the CRT listed in the manual. I'm thinking mine came from my local air force base as it has a sticker warning not to measure line voltage because the case is grounded and it has a flat faced CRT in it.

I am at my wits end with the scope. Other than removing the focus and intensity controls from the chassis and seeing if the problem is solved I don't know what to do.