Are there any repair facilities that are still repairing these units? Or should I say dinosaurs.
Try National Test Equipment:
https://www.ntecusa.com/Test-Equipment-Repair-Calibration/Calibrators/Agilent-(Keysight)-8902A/2C15F5F4070C6FC61948DF00C427CC7F
Yeah, National Test Equipment does really good repairs on obsolete stuff.
TRESCAL, INC.
5965 Shiloh Road East
Alpharetta, GA 30005
Phone: 678 341 6090
I have used National Test Equipment and their repairs were effective. They did try to retain some defective components of ours. I generally will not allow a vendor to do that.