[Coco] My beloved coco seems to have had a stroke

[Robert Gault]

Gene Heskett wrote:
> Tonight, on powering it up (it has hdbdos) it shows the HDB-DOS1.0A in the
> middle of the screen, and essentially stops.  It usually waits for the hard
> drives to spin up and do their initial calibration sweep, and assert the
> drive ready signal, at which point that 15 second countdown of marching
> dots that gives one time to hit the key indicating what to boot from, or
> take the default hard drive boot.
>
> I can hear at least one drive do that head scan, but the upper drive HD 1
> never turns off its little led unless I remove its drive cable.  HD 0 does
> flash it once at powerup, for maybe 1/4 second.  And the countdown dots
> never start.  Ever.
>
> Hitting the reset button at that point, then typing DOS0 gets an instant
> I/O error, which may be that I need to do a drive off or drive on first,
> I've forgotten which enables the first 4 floppy drives.  Power supply
> voltages to the multipak, and to the drives are good, the 5 volts is about
> 5.08, the +12 for the drive motors is about 11.98.
>
> Next step suggestions please.
>
> Cheers, Gene
>

Gene,

What happens if you disconnect HD0 from the system? Do you then have access to 
the other drive?

I've a very old SCSI Tandon TM 252 drive as one of two in my system. At random, 
it gets stuck on the landing pad and I have to move the heads manually to get it 
active. Same symptoms as yours, drive light always on but no I/O.