zippysticks
Veteran Member
Folks,
My Northstar MDC-A4 floppy disk controller no longer works - Any ideas what to look for beyond the list below ?
Both drives spin up on start but no attempt to boot from drive 1 - multiple resets occasionally initiate the drive 1 light on but sometimes the drives will not stop spinning after the timeout period.
I have tried a few obvious things including:
1. Substituting with My MDS-AD3 controller from another machine which works just fine so I'm sure its nothing else on the Northstar backplane or the floppy drives.
2. Removing and reseating all the 74 series IC's in their sockets and the three 74S287 PROM's
3. Voltage regulator and tantalum cap seem ok too.
Worth noting I don't have a monitor PROM on the system CPU card so have no way to probe memory content or run controller tests.
Thanks in advance.
My Northstar MDC-A4 floppy disk controller no longer works - Any ideas what to look for beyond the list below ?
Both drives spin up on start but no attempt to boot from drive 1 - multiple resets occasionally initiate the drive 1 light on but sometimes the drives will not stop spinning after the timeout period.
I have tried a few obvious things including:
1. Substituting with My MDS-AD3 controller from another machine which works just fine so I'm sure its nothing else on the Northstar backplane or the floppy drives.
2. Removing and reseating all the 74 series IC's in their sockets and the three 74S287 PROM's
3. Voltage regulator and tantalum cap seem ok too.
Worth noting I don't have a monitor PROM on the system CPU card so have no way to probe memory content or run controller tests.
Thanks in advance.
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