CelGen
Well-known member
I need someone with one of the 20mb Miniscribe 8425SA drives to help me verify something.
I'm running into a number of these drives which are cosmetically okay. They pass self-test and when put into exercise mode they function totally fine. The problem comes up when you try to operate it normally. Self-test completes, homes the head and then does a weird semi-step once a second which hangs up the SCSI bus and the host machine, making it impossible to read or format. Being a stepper motor design it doesn't rely on embedded servo tracks. Simply "step to x and hope the data is there" and with the drive confirmed to be mechanically fine the problem can only be coming from the logic board itself. The only field replaceable part is the 14 pin DIP EPROM There's a possibility that a few bits have flipped after something like 30 years. I need a dump of the EPROM on a known working drive to confirm this.
I'm running into a number of these drives which are cosmetically okay. They pass self-test and when put into exercise mode they function totally fine. The problem comes up when you try to operate it normally. Self-test completes, homes the head and then does a weird semi-step once a second which hangs up the SCSI bus and the host machine, making it impossible to read or format. Being a stepper motor design it doesn't rely on embedded servo tracks. Simply "step to x and hope the data is there" and with the drive confirmed to be mechanically fine the problem can only be coming from the logic board itself. The only field replaceable part is the 14 pin DIP EPROM There's a possibility that a few bits have flipped after something like 30 years. I need a dump of the EPROM on a known working drive to confirm this.