Thanks, I understand now.
600-15 is the board I had made, original was missing from the second 5327B, it's the voltmeter display control board (A14), it's well documented in the Artek manual that got leaked on the web. The picture in the manual shows a 16 pin divider IC, but only half is used, most have the 8 pin divider IC, I finally found a picture showing the 16 pin IC fitted, sorry it's crap quality, archived from ePay years ago by me.
I've found the older manual you were looking at, it's crap as you know, seems to have multiple scans of the manual stuck together, the 600-07 & 600-24 are called A7A & A7B function control in that manual, seems to be a mix of TTL logic, ECL logic, with a RCA trannystor array.
I would never have guessed it had a service position for the second board, that answers the how the heck do you work on this if it fails.
Later 600-31 combined A7 function control board is all ECL logic, with several custom HP level translators.
P.S. I thought I had a preliminary manual for the older 5326A/B, but couldn't find it the other day.
David