Keith Hui wrote:
SST 39SF020A
..
I have not been able to get another of the same chip for backup.
Must not be exactly the same, any parallell 5V flash will work fine.
SST39SF040 may be easier to find. Am29F040, AMIC A29040, EN29F040A or ST M29F002B would work too. Where are you located?
//Peter