After cleanup, everything worked fine — except that the PSU’s 5 V became 6.5 V during the accident, and the EPROM with LocalTalk interface firmware died, connection between VCC and GND ...

But there are simpler ways to generate patterns, including an old-fashioned EPROM, as [DrMattRegan] points out in a recent video. Generating video signals is an exercise in periodicity.

Turn on the EMP-20 Programmer (in back). There is a power light next to the ZIF socket (Zero Insertion Force) and the ZIF’s handle should be straight up. Set the "T" switch on the shelf next to the ...