were unable to determine the cause of the "Sad Mac" as it had no hex code listed below it... just garbage print.

Click to expand...

There are a number of known issues that can cause a sad Mac. The garbage component suggests multiple problems. But let's assume the most basic.

Any number of the RAM chips could be bad. Not knowing the exact ones at fault would make for a painstaking replacement.

I presume you have adjusted the analogue voltages back to optimal after your repairs? That is a common cause of the sad Mac. Also, remove the programmer's switch if installed.