Using ST-225 in a CBM D9090 hard drive

From: B. Degnan (
Date: 2006-10-01 01:21:15

I have given up trying to find a 6-head Tandon 603s, and I decided to use a 
4-head ST-225 because they are easier to find.  I used a B-128 to format 
the drive.

1) On the controller (top) I snipped J14 jumper to make the D9090 think it 
was a D9060.  This modification is necessary because the D9090 controller 
is set to use a 6-head drive.  Clipping J14 converts the controller into a 
de-facto D9060 which expects a 4 head drive.  The D9060 came with Tandon 602s.

2) I removed the Tandon 603s hard drive that originally came with the 
drive, reassembled w/o cover.

3) ran a quick test to be sure that the drive was put back together safely:

 > ?ds$ [enter]

73, CBM DOS 3.0.0 etc

4) I used the following command:

 >header "degnan",d0,i01 [enter]

Are you sure?  y [enter]

5) Both drive lights came on solid green, no visible flashing, and I was no 
longer able to type at the computer.

6) I looked inside the drive at the light of the ST-225, also solid

7) I listened closely, heard nothing other than the drive spinning.  A 
stethoscope would have been useful here.

8) After about 15 minutes I noticed that the drive light would flick once 
every 10-20 seconds, and the drive would simultaneously click very softly.

9) Left room, had dinner

10)  Came back about ~45 minutes later, the drive had returned control to 
the computer.

11) ran a DIRECTORY command

19441 blocks free

..geez I think I went through 10 drives before I found a working drive (by 
first testing in an IBM XT).  Hopefully this will help people in the future 
with the same project.  There isn't really anywhere on the web that clearly 
explains the process of replacing the Tandon 603s brick with the ST-225.

Bill D

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