WTD Tandon 603s Hard Drive for Commodore CBM D9090 external HDD

[Ethan Dicks]

On 12/22/05, B. Degnan <billdeg at degnanco.com> wrote:
> I am trying to restore a CBM D9090 external hard drive.  The controller
> cards seem OK, but I get a "?  bad disk" error when attempting to
> initialize (using a B128).

Given the age and fragility of the TM602/TM603 drives, that's not surprising.

If you are hearing the drive spin up (no stiction), one thing that
failed on one of my Tandon drives from a D90x0 was the optical track
zero sensor.  I had it professionally repaired over 10 years ago for
$75 including new media, back when repairing small drives was
practical.

In the long term, however, a new mechanism is probably your best bet.

> If no Tandon 603s is available, does anyone
> have experience and success replacing the original stock Tandon 603s drive
> with another drive?

Yes.

> I have read differing opinions about what drives are
> compatible with the D9090.  I tried a working ST 412, but I think that this
> is too new.  Did not work.  The drive I believe has to be 7.5 to 10 MB with
> even heads.

My experience is that if you strap the D90x0 board to expect 4 heads,
you can use an ST-225.  I _think_an ST-251 may work for a 6-head
drive.  Without tweaking the firmware on the "DOS Board", you are
still limited in how many cylinders the drive looks for - so the
capacity will not change from 5MB or 7.5MB (4 heads/6 heads).  The
good news is that ST225 drives were uber-plentiful back in the day, so
it still shouldn't be difficult to find, for an ST506/ST412-interface
drive.

I save every ST-225 and ST-251 that happens past, largely for things
like the D90x0 and DECmate IIs, etc.

Give a Seagate drive a try - it should work for you.

-ethan