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

[B. Degnan]

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

Bill D