Much has been written about the original RAM board, HERE is a good example
This was my only Icom rig at the time I originally compiled this web page, though I sold it on late in 2018 to a fellow CW enthusiast.It had been owned by me since "nearly new" around 1990. This has a splendid receiver, and I installed CW filters and the internal switch-mode PSU. Other IC-751A owners have complained about the performance of the radio with the internal PSU installed, but I have never experienced any problems with this, to date.
A problem with this radio for a number of years has been the famous Bad Cap problem. Another entry on my "To Do" list!
(If you find a broken link when looking up the "Bad Cap" problem, look out for Icom Knowledge Base article number 5B9F593A21:- Icom often shuffle the pages on their web sites! I have a local copy here.
More recently I replaced the Icom memory unit with the PieXX unit as I felt that the original lithium battery must have been on borrowed time, though the battery voltage appeared to be perfectly OK at the time of replacement.
Much has been written about the original RAM board, HERE is a good example