I'm a student in a research lab working on getting some test equipment set up. The system has a GE Series 90-30 controller and we have found that our power supply is faulty. PN: IC693PWR321AA. I have been searching around for a replacement and found many parts with PN IC693PWR321 but few with the -AA. Is there any difference between these models that would cause the PLC not to work? (I'm not exceptionally knowledgeable in the PLC area). Thanks!