Greg,

Are the installed RAMs 6264 types? If so, just two of them installed is a valid configuration,
so you could remove all but two and swap those out to see if you have a bad RAM chip. You can see the
valid configurations and jumper setting in the service manual.

The service manual mentions that U84 and some other gates are not used in the Polaris, and this circuitry
was for something that Fender was developing. I think this is the circuit that was driving PREQ, so
probably it's OK to be sitting high.

Bob