Yes, I'd expect complementary square waves on both outputs (180°).
Anyhow, if you apply the signal to channel B, you should see either this correct output (square wave), or also noise, like on channel A.
This would indicate, if the whole IC is dead, or the upper OpAmp only.
As a replacement, you'll need a double fast comparator.
This one might be an ECL line driver, which might not be available anymore, as of today.
Frank