Hello Olaf,
The repair/service kit for the HP 8660 series mainframe part HP's part number 08660-60070. I've attached a photo of one I found online (photo taken from .)
The repair/service kit for the HP 8660 modulation and RF plug-ins and frequency extension module (a YIG package required to support the 1.3 and 2.6 GHz RF plug-ins) was called the HP 11672A. A photo (taken from a defunct ebay listing) is attached.
The 11672A kit provides the two (heavy and rather proprietary) cables needed to bring the three modules (modulation, RF and frequency extension) out for repair/testing. The HP 08660-60070 board kit is extender boards needed to bring the (numerous) plug-in PC boards in the mainframe up for repair/testing.
The connectors on the two large cables in the 11672A kit I believe were made by Winchester and include a number of coaxial cable contacts.
Good luck in your HP 8660C repair - they are nice machines, although I've found that their CW (but not modulation) capabilities can be somewhat duplicated by a TinySA Ultra and a small number of SMA attenuators.
Dave
