Heres the video of the burned up Sylvania chassis we found.
http://youtu.be/uCPYnQpJmFE
This is a bit newer but still, this is why you never leave a vintage set on unattended. If you have to for some reason, fuse everything.
I have a bulletin from Zenith on a mod for that hv regulation. I should scan that and post it.
I will say this about Sylvania,,,I am a fan, the sets have a great picture but they can be super hard to fix. I have a fairly large collection of them, they are all the newer Gibraltar series tube chassis