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SWTPC MF-68 Assembly Instructions Manual

For swtpc 6800

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The MF-68 Disc System is a dual mini-floppy disc system designed for a SWTPC
6800 Computer System.
The MF-68 consists of three major parts: the controller, the chassis and
power supply and the drives themselves. The drives come pre-assembled and require
only minor jumper changes to be used. The power supply is assembled partially on a
small printed circuit board and partially thru point to point chassis wiring. The
controller is assembled entirely on a 5 3/4" x 5" circuit board that will plug into
an I/0 slot on the computer's mother board. Connection between the controller and
the drives is made via a 34 conductor ribbon cable.
When assembling the unit, work first on the controller board, then the power
supply and finally the drive programming and chassis assembly.
When the MF-68 disc system is being assembled, work on only one part or board
at a time. The MOS integrated circuits supplied with this kit are susceptible to
static electricity damage and for this reason have reason have been packed with
their leads impressed onto a special conductive foam or possibly wrapped in a
conductive foil. In either case, do not remove the protective material until told
to do so later in the instructions.
NOTE: Since all of the holes on the PC board have been plated thru, it is
only necessary to solder the components from the bottom side of the board. The
plating provides the electrical connection from the "BOTTOM" to the "TOP" foil of
each hole. Unless otherwise noted, it is important that none of the connections be
soldered until all of the components of each group have been installed on the
board. This makes it much easier to interchange components if a mistake is made
during assembly. Be sure to use a low wattage iron (not a gun) with a small tip. Do
not use acid core solder or any type of paste flux. We will not guarantee or repair
any kit on which either product has been used. Use only the solder supplied with
the kit or a 60/40 alloy resin core equivalent. Remember all of the connections are
soldered on the bottom side of the board only. The plated-thru holes provide the
electrical connection to the top foil.
( )
Before installing any parts on the circuit board, check both sides of the
board over carefully for incomplete etching and foil "bridges" or "breaks".
It is unlikely that you will find any, but should there be, especially on the
"TOP" side of the board, it will be very hard to locate and correct after all
of the components have been installed on the board.
( )
Attach all of the resistors to the board. As with all other components unless
noted, use the parts list and component layout drawing to locate each part
and install from the "TOP" side of the board bending the leads along the
"BOTTOM" side of the board and trimming so that 1/16" to 1/8" of wire
remains. Solder.
Scanned and edited by Michael Holley
Southwest Technical Products Corporation Document
Assembly Instructions MF-68 Disk System
Controller PC Board Assembly
Feb 17, 2004
1
Circa 1977

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Summary of Contents for SWTPC MF-68

  • Page 1 When assembling the unit, work first on the controller board, then the power supply and finally the drive programming and chassis assembly. When the MF-68 disc system is being assembled, work on only one part or board at a time. The MOS integrated circuits supplied with this kit are susceptible to...
  • Page 2 Install all of the capacitors on the board. Be sure to install the electrolytic and tantalum capacitors exactly as shown on the component layout drawing. Solder. Install the transistor and diodes on the board. The diodes must be turned so the banded end corresponds with that shown on the component layout drawing, and the transistor must be turned to match the outline on the component layout drawing as well.
  • Page 3 Now that the power supply has been assembled you are ready to program and install the drives. The mini-floppy drives come pre-assembled and tested and require no circuit modifications to work in an MF-68 System. The drives do need to be programmed, however, to allow multiplexing of the drive select signals to selectively enable multiple drives.
  • Page 4 MINI MINI 25060-1 25060-2 The number -1 or -2 denotes the circuit board revision number follow the correct instructions below for the drives you have. 25060 -1 boards ( Both drives must be -1 ) At the bottom left corner of the board you will notice what looks like an IC made up of jumpers in a socket.
  • Page 5 On the other drive bend straight the pins going to DS1 and DS3 - all others should be left as they are to complete the jumpering of DS2, T1, T2, T3, T4 and T5. Re-install the jumper block. In the center of the board you will notice two small connected pads marked MUX.
  • Page 6: Final Assembly

    Combination of one 25060-1 and one 25060-2 Board. If you have one -1 board and one -2 board a combination of the above instructions should be followed. First take the -2 unit and turn it so that the edge connectors are nearest you. At the bottom left corner of the board you will notice what looks like an IC made up of jumpers in a socket.
  • Page 7 Computer Interconnection In order for the MF-68 to work properly with an SWTPC 6800 computer one minor modification needs to be made to the mother board. Power down the computer and carefully remove the mother board.
  • Page 8 At least 16K of memory must be installed in the computer. After connecting the disk to the computer you are ready to use the MF-68. If at any time the disk fails to operate as described, power down the system and re-check all assembly.
  • Page 9 Do not touch or attempt to clean the disk surface. Abrasions may cause loss of stored data. The MF-68 uses the ENABLE line from I/0 position 5 as a control line. Care should be exercised when using I/0 slot 5 for other devices. A parallel printer...
  • Page 10 Parts List - DC-1 Disk Controller Resistors 4.7K Ω 1/4 watt resistor ____ 1M Ω 1/4 watt resistor ____ 750K Ω 1/4 watt resistor ____ 150 Ω 1/4 watt resistor ____ 150 Ω 1/4 watt resistor ____ 150 Ω 1/4 watt resistor ____ 150 Ω...
  • Page 12 The P-200 Power Supply is a fixed voltage power supply designed to be used with several. SWTPC kits. The P-20OMF version is supplied with those parts required to power the MF-68 Dual Floppy Disk System. The P-200 MF provides the following outputs: +12 VDC + 5% @ 3.0 amps...
  • Page 13 Attaching the Connector to the Power Transformer Cut all of the power transformer secondary leads to a 7" length and strip the ends of the wires so that only 1/8" protrudes beyond the insulation. Attach and solder the specified connector pins to each of the leads using the table below for reference.
  • Page 14 Tighten all of the capacitor clamp mounting screws. Using #10-32 X 1/4" screws attach three terminal lugs to the (+) terminal and five terminal lugs to the (-) terminal of capacitor C3. Also attach two terminal lugs to the (+) terminal and six terminal lugs to the (-) terminal of capacitor C4.
  • Page 15 Without having anything plugged onto power connectors JO or J1 and after making sure these connectors are not inadvertantly touching anything they shouldn't be, plug the line cord into a wall outlet and turn the power switch Using the metal chassis as a ground reference measure the following voltages on the two power connectors listed below.
  • Page 16 Parts List P-200 MF Power Supply Resistors ____ 240 ohm 1% resistor or 243 ohm 1% ____ 2030 ohm 1% resistor or 2000 ohm 1% ____ 240 ohm 1% resistor or 243 ohm 1% ____ 2030 ohm 1% resistor or 2000 ohm 1% Diodes ____ 1N5402 high current diode...
  • Page 17 WIRE FROM LENGTH PART PART TERMINAL STEP GAUGE TERMINAL SOLDER SOLDER 8 1/2 ” PC board C3 lug 7" PC board 6 1/2" PC board 9" PC board 8" PC board 9" PC board C4 lug 11” PC board C3 lug 9"...
  • Page 18: In Case Of Problems

    IN CASE OF PROBLEMS If your MF-68 fails to operate properly we suggest that you first go back and double check all parts. Be sure that they are turned as shown on the drawings and that they are the correct part number. The majority of problems turn out to be incorrect assembly.
  • Page 19: Shipping Instructions

    SHIPPING INSTRUCTIONS Pack in a large carton with at least 3 inches of padding on all sides. Do not attempt to return the kit in the original box. We will not service a kit if there is any postal damage until the claim is settled. Include all relevant correspondence and a brief description of the difficulty.