You'll have to wait until Jim Yanik comes around for comfiration, but I
suspect the CRT.

Actually, that is not bad luck, IIRC there are some very hard to get
ICs for Tektronix scopes. Think it was the horizontal amp. Your problem
has nothing to do with that, so hopefully either you have ICs for
another scope or can find a CRT for yours.

Once sure of the problem, ESI in Cleveland OH has alot of Tek stuff.
You might try Skycraft in Orlando FL but they don't have as much, or
didn't last time I was there. Other than that there is always eBay.
There are other places, I just don't know of them.

Good luck with it.

JURB