That raises a question I wanted to post and forgot to.
A few weeks ago, I scored a mint 2445B with only 270 hours.
The only problem I could find was a failure of the beam finder switch that remained in the activated state.
It was fixed by cleaning.
But while the scope was open I left it running to check if everything was ok, obviously with a fan directed on U800.
And after about 15m, U800 was still cold.
So I stopped the fan a few minutes and U800 was still at about 30°C.
After about half an hour, I could still hold my finger on it and it felt just warm, I didn't think to take a real temp measure though.
So I'm wondering if there are different versions of U800, (based on IC dates, scope was build in '94) or if the legendary U800 meltdown only happen with certain settings ?