pucho812
Well-known member
Anyone have schematics for the ISA 428, 4 channel mic Pre? One arrived from a thrift store and it powers on but every led comes on and stays on and none of the switches work. I assume it’s psu related. I can measure +/-15vdc on the 5532’s which is within working voltage for the ic but not sure if that’s correct. Also not sure what else the psu outputs other then phantom power. I know they are prone to failure from heat. But wouldn’t be bad to have working.