SS to DS Drive

~~~ |||||||||||||||||||||||||||||||| || ST DISK DRIVE CONVERSION || || SINGLE TO DOUBLE SIDED || ||||||||||||||||||||||||||||||||

The single sided Atari SF354 disk drive can be converted to a double sided drive for $94. It is completely equivalent to the SF314 except that it uses far less power. The SF354 contains an Epson SMD130 drive and the SF314 contains an Epson 140 drive. In addition, both drives contain a connector board at the rear of the drive housing which interfaces the Atari cables to the headed sockets which plug into the Epson drive.

The boards also have jumper wires which tell the 520ST what type of drive is connected. The cases for both drives are identical (except for the SF354/SF314 marking on the outside.) There are eight Epson SMD-100 series disk drives. The SMD-130 and SMD-170 are interchangable single sided drives. Similarly, the SMD-140 and SMD-180 are interchangable double sided drives. The difference is that the SMD-130 and SMD-140 are intended for AC powered equipment and consume 1.3W on standby and 6.9W on read/write. The SMD-170 and SMD-180 are designed for use with both AC and battery powered equipment and use 0.3W on standby and 2.9W on read/write.

A good source for the Epson SMD-180 drive is:

                    Halted Specialties Co. Inc
                       827 E. Evelyn Avenue
                          (408) 732-1573
                       Sunnyvale, CA 94086

The cost is $89 plus $5 shipping. They accept phone orders using a credit card and ship via UPS. Since the cost of a SF314 is about $219 the conversion results in a considerable saving. The only problem is what do you do with the old single sided drive?

To convert the drive, proceed as follows:

  1. Remove the four screws around the perimeter of the SF354 disk drive and gently lift the rear of the cover while lightly pressing in the disk connector sockets at the rear. The sockets and switch should should pop free and then the top can be unhocked from the disk active LED and disk eject switch at the front.

  2. Carefully unplug the two socket connectors between the interface board and the rear of the SMD-130. Use a small, flat bladed screwdriver to gently and evenly pry them free. Looking at the top of the board in the lower left-hand corner is a place for a jumper wire marked W1 between locations SG and FG. Connect a piece of wire between these point and solder it in place. Turn the board over and rotate 180 degrees. Find the four parallel jumper wires on the right hand side. Remove the first and third wires, either by cutting them away or unsoldering them. This completes the modifications to this board.

                                                  1    3    1    3      

    | O O O O | | O SG- : new jumper x L | x L | | | : W1 x remove jumper x 2 | x 1 | | | : J5 J6 | existing jumper O O O O | | O FG- 2 4 2 4 | |_____________________ ______________________|
    top bottom

  3. At this point, you have to decide how functional you want the drive active LED to be. You will probably have noticed that the disk active LED is on the left front on the SMD-180 and on the right front on the SMD-130. You have three choices.

    a) Forget about it and use you ears to tell you when the drive is active; b) Drill a small hole through the plastic front at the location of the SMD-180 LED; c) Unsolder the LED on the SMD-180, extend it on wires to the SMD-130 location and epoxy it in place behind the old LED window. I used clear epoxy with a small piece of silver foil as reflector to achieve sufficient LED brilliance. I did not change LEDs as I suspect the SMD-180 LED has a far lower driving current. To remove the LED, I had to remove the two screws holding the board, the two cables pluged in by the stepper motor, tilt the board up and use a solder sucker to get it out. If you're willing to do this, you don't need further instructions!

  4. Remove the three screws on the bottom of the disk drive case and lift off the SMD-130. Remove the two screws holding on the RFI shield and slide it off to the rear. Now slide it onto the new drive and put the two screws back in place. Use a small Phillips screw driver (about 1/8" diam) to loosen the two screws holding on the plastic disk case front from the SMD-130. They are accessable from the top looking vertically straight down just behind the plastic front. Once the screws are completely free, gently lift the plastic front off the SMD-130 taking the screws along. Look behind the eject button and note that it is attached by two plastic hooks through a rectangular hole in the metal eject lever. Very gently compress the two plastic clips together, remove the plastic knob and push into the hole on the SMD-180 eject lever. Install the plastic drive front on the SMD-180 by reversing the removal procedure. Screw the SMD-180 onto the case bottom using the three retaining screws. Be careful to position it as far forward as possible so that the plastic front touches the lip on the case bottom.

  5. Plug the two connectors from the interface board into the rear of the SMD-180, hook the top cover over the LED and eject button and lower the rear over the interface board. Once in place, do up the four screws on the bottom and the SF354 is now a SF314. Hook up and enjoy.

John Hissink


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