Good morning.
Sorry about the first photo I post but it is not my oscilloscope.
I get it because as I saw it on eBay, I tried to get in touch with the new owner to know if he has the service manual.
However I had no luck as he don't have it and I forgot to delete de photo.
The next two photos are from the problem that my scope has.
This big and very bright dot is the only thing that appears on the screen.
Even changing X and Y position of the 4 channels, I just get this: no different lines or even spots, just this big and very bright central spot.
I just took the pictures and turn it off before I burnt the tube that was just perfect before this problem.
It seems a X and Y deflection problem...
That's why it was so important to have the schematics diagrams...