Solution:

Your problem is caused by PPC-100. The power supply of PPC-100 just supports +5V, +12V and -12V, but -12V of power supply doesn't connect to ISA bus, that is to say, there is no -12V in ISA bus. However, PCL-746+ needs -12V to work normally, but it can't get -12V from ISA bus, that's why your PCL-746+ doesn't work well. The solution is that you can connect -12V of power supply to B7 of ISA bus or B5 of expansion slot (you can check that B7 of ISA bus and B5 of expansion slot are the same) to overcome this problem.