The Sequential Circuits Prophet 5 Rev 3.3 normally uses three RAM chips of two different types to hold program memory, all of which are out of production and increasingly difficult to find. Typical F-RAM / Flash RAM modules intended to replace a single RAM IC won’t work in the Prophet 5 because of the more complex addressing associated with it originally using three RAM chips. Our Prophet 5 Rev 3.3 “Memory Liberator” includes the necessary logic that allows it to replace ALL THREE of the original RAMs with the single modern ferroelectric RAM chip housed on our board, eliminating the need for a battery entirely. This retrofit plugs into the empty 24-pin socket on the Rev 3.3 CPU board and interfaces with three wires on the “ugly mod,”* so does require soldering of 3 wires to install.
instructions here: Prophet 5 Rev 3.3 Memory Liberator Installation
*The “ugly mod” is what Sequential calls a modification wherein a certain IC is piggybacked on top of another and wired to a couple of other places, which exists in all Rev 3.3. units and is performed when upgrading a Rev 3.2 Prophet 5 to Rev 3.3.
Note that this version works with Rev 3.3 Prophet 5s only. If you have an earlier Prophet 5, you will need the other version.