I agree these caps are the most failure-prone parts in the 3456A, and also the 3455A. Sometimes they also cause damage to other parts like the associated three-terminal regulators. Don't be surprised if there's still more to fix after cap replacement - but usually easy to find. I had one where an LM339 status comparator was shot - I suspected over-voltage or reversal of an input polarity during the cap failure, even though it wasn't obvious how it could have done that. The diagnostics instructions in the manual worked very well and led quickly to the faulty part. Ed