Tek 2465B intensity problem
 

I have a problem with my 2465B. The display went blank so I got the
service manual and started following the flow charts. The took me to
a dead end but gave me a hint. Turning up the grid bias did bring the
display into view and the scope seems to be working other than the
intensity. The intensity adjustment makes no difference at all. I
followed that adjustment in the schematics and the signal is called
"DI" until it gets to U650. It seems to be a non-TTL level signal (to
low). I can see something changing in the signal when I adjust the
Intensity, but can make sense of it. It appears to have some kind of
small digital component at a very low level. Or perhaps that is my
problem. I could not find any info on this signal in the manual.

Can anyone tell me what the DI signal is supposed to look like?
Should adjusting the intensity affect the "Brightness" signal coming
out of U650? I just don't get enough info in the manual on these
signals or where DI goes after U650.

Thanks!