Kevin,
I have been repairing and upgrading the PS 90,75 and ICS sub amps for some time now 10
+ years. I realize your post is almost a year old and you may have found a solution. Just for your information and others looking for repair for these units. I also have some of the last remaining inventory for the upgraded digital boards and IR sensors. I can't offer a swap due to the limited supply of parts but can offer a repair/restoration of your existing unit. These are a well-designed amps but went through three revisions They still require revisions to maintain stability, all covered in the repair/restoration.
