the problem is usually caused if you remove the installation and revert back to the original memory as the upgrade squeezes between the MMU and socket pins when installed thus pushing the pins back so when you remove it they don't make contact with the MMU
can easily be solved by bending out each socket pin with a ...pin! oh and a magnifying glass!
sadly i'm not near Suffolk which is a shame as i'd love to see how an oscilloscope could help me sort this machine
anyway i shall probably start with the CPU just as soon as i can find a definate working one
