Ouch, that's bad news. The UCIC is the TDC (time-digital-converter), the chip where all the magic happens... Apparently it's been made by or specifically for HP, their part number is 1SL5-0125. There's probably little chance sourcing one of these NOS. I'ld rather watch out for a cheap 53310A, maybe a parts / defective unit. I have never heard of one of these chips failing but this doesn't mean much. Are you sure it's the UCIC and has your technichan the experience to track the fault down to this semiconductor? Please don't get me wrong, I'm not questioning your tech's skills but the 53310A is a mighty complex machine, and even with the CLIP (component level information package) available, the operating principles, especially around the UCIC, stay pretty much in the dark. There doesn't seem to be a datasheet or any in-depth description of this semiconductor available. At least I wasn't able to find one.
What's the actual problem, does the MDA report some errors or is it simply "dead"?