To get something a little more constructive in this thread:
The 'does not boot unless cache turned off' problem may be due to mismatched ZIP RAMs. When the first bank consists entirely of static column (SC) chips Ramsey's burst mode is turned on - but it will only be used for filling the cache.
A problem arises when the rest of the RAMs are not 100% SC (xx4402) but fast page (FP xx4400) - the burst will not work and the machine will crash.
Check if ALL chips are SC and if they're mixed move one of the FP chips to the left frontmost socket.
As to
SCSI cable length: we're talking SCSI-1 here, so the cable may be up to 6m (nearly 20'). I'd stay below 3m (for Fast SCSI) to make sure.
Double and triple check termination, some A3ks have misprinted socket labels, so terminator (resistor) packs installed 'correctly' may not work. The 220 Ohm side must go to termpower (5V), the 330 Ohm side to GND. Check whether termpower reads 5V (or close to), the fuse may be blown. If you have the chance try cable terminators, preferably active ones. Most have a LED to show whether termpower is on.
