There are very few versions of the manual for the 8840A (12/91 revised 5/97), and it is incomplete in terms of schematics. But you can combine it with the 8842A (12/91 revised 7/96) which is complete.
The main PCBs are slightly different, and some of the option boards are jumpered specific to the 8840A/AF (AC Converter) and/or have different ROMs (488 card) but the schematics are the same.
But I know of no material changes to the main PCB from 1984-85 to 1997-98. Your meter may have been re-caped, but of the 30 meters I have tested, I found only 2 that needed new caps (and not all of them).
I dont subscribe to the "re-cap" everything, particularly industrial equipment. I typically measure, with a pair of HP3457A scanning system meters), AC & DC values of the 6 main input filter capacitors
and the 10 regulated DC supplies. If these meet the Fluke specs I dont tough them.
The only thing I have found that changed is the supports under the main PCB in the transformer area. Meters up to about 1988 have only a white nylon hex standoff to keep the PCB from sagging. Later
models have a machined Delrin transformer support. I suspect a known failure was de-laminating of the transformer solder joints. (I always re-solder the transformer if I poen a meter.)
kjo KO3Y