Project complete.
Replaced U700, and the trace came back to normal.
A BIG thanks for everyone's help!!!

Just an additional story here.
You all remember that I bought this scope from Alexander Schonfeld in California (ebay username - 2465b), who up-modded the 2445B A1's frequency, without telling the customers.

Well, I got in contact with him, and I suggested to him that the right thing to do, would be to send me the new IC's free of charge.

He did, so I do say that the man is making amends in a small way, and I appreciated that.