@timtiger to test the 1Hz pulse, you just need to use the multimeter in DC (not AC) mode and in a voltage range greater than 5V. The multimeter will tend to react quite slowly so you might see it switch between around 4 volts and 1 volts. The important thing isn’t the voltage but the fact it changes roughly every 0.5 seconds between high and low.
Re your snooper test, I wonder if you’ve got some issues with the RAM multiplexers rather than the RAM itself.
Re the Rominator, beware that the PCB might be a bit thinner than the stock ROM and so it might need some extra support to get good connections with the socket. I’ve personally never had an issue with this but some people use 3D printed clips or rubber bands etc. Also be aware that you need to make some changes to system software in order to boot System 7.5 with the Rominator.
It seems to me that you may have more than one issue going on here which always makes it challenging to fix.
Re your snooper test, I wonder if you’ve got some issues with the RAM multiplexers rather than the RAM itself.
Re the Rominator, beware that the PCB might be a bit thinner than the stock ROM and so it might need some extra support to get good connections with the socket. I’ve personally never had an issue with this but some people use 3D printed clips or rubber bands etc. Also be aware that you need to make some changes to system software in order to boot System 7.5 with the Rominator.
It seems to me that you may have more than one issue going on here which always makes it challenging to fix.
