Are you an owner of a SH-204? If so, have you found that you need more storage room than 20-megs nowadays? I might have the answer you've been waiting for! The following are a compilation of posts from Tim Onders (Control Services) on how to upgrade your SH-204. (From CIS)
Just keep your eye out for a used mechanism and upgrade. I managed to replace my SH-204 mechanism with a 71 meg Priam for about $300 that way.
Simple instructions: Inside the SH-204 case are four parts.
1) The drive mech, mounted towards the front on the bottom 2) The power supply, also mounted on the bottom, in the back 3) The Atari host adaptor, a small board attached to the top of the case towards the back. The cable to the computer plugs into this 4) The drive controller card, usually an Adaptec MFM controller. Mounted on the front top of the case, it has a little LED that sticks through a hole in the front of the case.
Things are interconnected in the following manner:
o The power cable goes into the power supply. Out of the power supply comes cables with little "Molex" type connectors. These connectors supply the power to the other parts.
o The Host Adaptor has three connections: power, from the power supply, the connector for the cable from the ST, and a big wide ribbon cable that goes to the controller card.
o The controller card does have four connections: The power connector, the big cable from the host adaptor, and two ribbon cables that go to the drive itself. There is one extra edge connector on the drive controller. This is for a second drive mech, which may or may not work with the Host Adaptor. I've never tested it. (I think it does though.)
o The drive has three cables, the power connector, the medium sized ribbon cable, and the small ribbon cable, both from the controller.
Now that you are oriented, we begin the tricky stuff. The only new part required to upgrade an SH-204 is a bigger MFM hard drive to replace the old one. A SCSI drive could also be used, but I have never been lucky enough to try that. I just bought a cheap Priam drive.
The toughest thing about the job is that Atari, in the 11 or so years that I have owned and worked on Atari machines, does not like to use polarized edge connectors. This means that it is possible to put a cable on backwards. Don't worry, I'll take care of that.
Carefully remove the small edge connector from the drive in the 204.
There should be a notch in the board on the drive. Mark the cable connector with a permanent marker with respect to this notch. If there is no notch, the board in the drive should mark pin 1. Mark the cable with respect to pin 1.
Repeat the process with the other ribbon cable, the medium sized one.
Finally, disconnect the power connector from the mechanism. If you haven't already done so, unscrew the drive from the bottom of the case. Be sure not to lose the little rubber shock mounts.
Now, just reverse the procedure with the new drive. Simple plug and play.
To use the new drive, you must get the formatting parameters for it to use with whatever utilities you use. The manufacturer is usually more than happy to provide this information. The ST even manages to squeeze more space out of most drives than a PC. My 62 meg Priam formats out to about 71 megs on the ST.
(Disclaimer: Any hardware modifications require some technical skill and should only be done by a service center or a qualified person. ST Report and it's authors makes no guarantees regarding the reliability of any hardware modifications appearing in this magazine. You, as always, perform the modifications at your own risk.)
The power supply in most Atari hard drives will support a larger drive mechanism, in my case it went from a 20 meg seagate to a 42 meg seagate (ST251) with no problem (other than having to go in and re-solder some seriously bad solder connections on the power supply). (From Gregg Anderson - Genie)