SWTPC MF-68 User manual

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Assembly Instructions MF-68 Disk System
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.
Controller PC Board Assembly
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 Feb 17, 2004
Southwest Technical Products Corporation Document Circa 1977

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( ) 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. Solder.
( ) Starting from on end of the circuit board install each of the three, 10 pin
Molex female edge connectors along the lower edge of the board. These
connectors must be inserted from the "TOP" side of the board and must be
pressed down firmly against the board. Make sure the body of the connector
seats firmly against the board and that each pin extends completely into the
holes on the circuit board. Not being careful here will cause the board to
either wobble and/or be crooked when plugged onto the mother board. It is
suggested that you solder only the two end pins of each of the three
connectors until all have been installed at which time if everything looks
straight and rigid you should solder the as yet unsoldered pins.
( ) Insert the small nylon indexing plug into the lower edge connector pins
indicated by the small triangular on the "BOTTOM" side of the circuit board.
This prevents the board from being accidentally plugged on incorrectly.
( ) The 34 pin ribbon cable connector should now be attached to the board.
Install the connector from the "TOP" side of the board and orient the
connector such that the pins face the top edge of the board. Solder.
( ) The crystal should now be installed on the board. Bend the crystal's leads at
a 90° angle approx. ~ inch from its body and mount from the top side of the
board. After soldering fasten the crystal to the board using a short piece of
stripped wire by passing the wire through the two holes next to the crystal.
( ) Install all integrated circuits, except IC1, IC12 and IC13. As each one is
installed, make sure it is down firmly against the board and solder only two
of the leads to hold the pack in place while the other IC's are being
inserted. Do not bend the leads on the back side of the board. Doing so makes
it very difficult to remove the integrated circuits should replacement ever
be necessary. The semicircle notch, dot or bar on the end of the package is
used for orientation purpose and must match with the outlines shown on the
component layout drawing for each of the IC's. After inserting all of the
integrated circuits, go back and solder each of the as yet unsoldered pins.
( ) Install integrated circuit IC13 and its heatsink on the circuit board. This
component must be oriented so its metal face is facing the circuit board as
is secured to the circuit board with a #4-40 x 1/4" screw, lockwasher and
nut. The three leads of the integrated circuit must be bent down into each of
their respective holes. The hole on the heatsink should be positioned to
allow maximum contact area between the regulator and the heatsink. Solder.

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NOTE: MOS integrated circuits are susceptible to damage by static
electricity. Although some degree of protection is provided internally within the
integrated circuits, their cost demands the utmost in care. Before opening and/or
installing any MOS integrated circuits, you should ground your body and all
metallic tools coming into contact with the leads thru a 1 M Ω1/4 watt resistor
(supplied with the kit). The ground must be an "earth" ground such as a water pipe,
and not the circuit board ground. As for the connection to your body, attach a clip
lead to your watch or metal ID bracelet. Make absolutely sure you have the 1 Meg Ω
resistor connected between you and the "earth" ground, otherwise you will be
creating a dangerous shock hazard. Avoid touching the leads of the integrated
circuits any more than necessary when installing them, even if you are grounded.
The tip of the soldering iron should be grounded as well (separately from your body
ground) either with or without a 1 Meg al resistor. Most soldering irons having a
three prong line cord plug already have a grounded tip. Static electricity should
be an important consideration in cold, dry environments. It is less of a problem
when it is warm and humid.
( ) Install MOS integrated circuits ICI and IC12 following the precautions given
in the preceding section. As each is installed, make sure it is down firmly
against the board before soldering all of its leads. Do not bend the leads on
the back side of the board. Doing so makes it very difficult to remove the
integrated circuits should replacement ever be necessary. The "dot" or
"notch" on the end of the package is used for orientation purposes and must
match with that shown on the component layout drawing for each of the IC's .
( ) Working from the "TOP" side of the circuit board, fill in all of the
feed-thru's with molten solder. The feed-thru's are those unused holes on the
board whose internal plating connects the "TOP" and "BOTTOM" circuit
connections. Filling these feed-thru's with molten solder guarantees the
integrity of the connections and increase the current handling capability.
( ) Now that all of the components have been installed on the board, double check
to make sure all have been installed correctly in their proper location.
( ) Check very carefully to make sure that all connections have been soldered. It
is very easy to miss some connections when soldering which can really cause
some hard to find problems later during checkout. Also look for solder
"bridges" and "cold" solder joints which are another common problem.
Since the circuit board now contains MOS devices, it is susceptible damage
from severe static electrical sources. One should avoid handling the board any more
than necessary and when you must, avoid touching or allowing anything to come into
contact with any of the conductors on the board.
( ) Now that the controller has been finished, assemble the power supply using
the P-200 MF instruction set.
( ) 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. Carefully remove both drives
from their boxes and turn the drives so that the edge connectors are nearest
you and so that the belt and pulleys are on the bottom. Immediately above J2
on the bottom right hand edge of the board you will notice the wording

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MINI MINI
25060-1 or 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. On one of the drives remove the jumper block
with a screw driver and bend upward (straight out) the pins that go to
terminals DS2, DS3, T1, T2, T3 T4 and T5. Do not break off these pins.
Replace the jumper block in the socket. This jumper will select this drive
for DRIVE #0, the -lowest number and most dominant give in the system. As a
double check the only position that should have a connected jumper is DS1.
In the center of the board you will notice two small connected pads marked MUX.
This small trace should be cut with a knife or razor blade.
This drive is now programmed as DRIVE 0

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( ) 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. This small trace should be cut
with a knife or razor blade.
This drive is now programmed as DRIVE #1.
( ) Go on to the final assembly instructions.
25060 -2 boards ( Both drives must be -2 )
( ) At the bottom left corner of the board you will notice what looks like an IC
made up of jumpers in a socket. On cane of the drives remove the jumper block
with a screwdriver and bend upward (straight ) the pins that go to terminals
DS2, DS3, and MX. not break these pins off. Re-install the jumper block into
the socket. As a double check the jumper block should have pins inserted only
in terminals DS1, HS and the unlabeled pin. There should be nothing plugged
into the HM position.
Directly above this jumper block you will notice what appears to be a 14 pin
IC in a socket. This is not an IC but is an array of pull-up resistors.
Carefully remove this array from its socket using a small screwdriver. This
array should not be reinstalled. This drive is now programmed as DRIVE 0.
( ) On the other drive bend straight the pins going to DS1, DS3, and MX.
Re-install the jumper so that HS, DS2 and the unlabeled pin have jumper pins
installed.
( ) Go on to the final assembly instructions.

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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. Remove
the jumper block with a screwdriver and bend upward (straight out) the pins
that go to terminals DS2, DS3 and MX. Replace the jumper block in its socket.
Directly above the jumper block you will notice what appears to be a 14 pin
IC in a socket. This is not an IC but is an array of pull-up resistors. Slide
a screwdriver under this array and remove it. It should not be re-installed.
This drive is now programmed to be DRIVE 0.
( ) Now take the -1 drive and bend up pins DS1 and DS3. Re-install the jumper
block. You will notice in the middle of the board two small connector pads
marked MUX. This trace should be cut with a knife or razor blade.
( ) This drive is now programmed as DRIVE 1.
FINAL ASSEMBLY
( ) Some drives have the printed circuit board held in place with four metal
spring clips. If yours is of this type use two rubber bands for each drive to
help the retaining clips hold the board in place.
( ) Now that both drives have been programmed you are ready to install them in
the chassis. DRIVE 0 should be installed first nearest the power supply. The
drive should be installed so that the jumper block is toward the TOP of the
chassis. Connect the power supply connector to J2 of the drive and mount the
drive from the bottom of the chassis using two 6-32 X 1/4 screws.
( ) Connect the other power supply connector to J2 of DRIVE 1 and install this
drive next to the first. Again orient the drive so that the jumper block is
toward the top. Use two 6-32 X 1/4 screws to secure the drive.
( ) Insert the 1 1/2 inch hole bushings in the rear of the chassis. Install the
bushings from the outside of the chassis.

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( ) Run the ribbon cable thru the 1 1/2 inch hole bushing nearest the edge of the
chassis so that both edge type connectors are inside the chassis.
( ) Install the 2 Tinnerman nuts to the chassis for cover mounting.
( ) Connect the two edge connectors on the ribbon cable to the drives. The
connectors must be installed so that pin #1 is toward the top of the chassis.
( ) The front panel piece should now be installed on the chassis using 6-32 x 3/8
screws, lockwashers and nuts.
( ) This completes the assembly of the disk system. Before the cover is installed
or power is applied you should re-check all assembly steps.
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. With a short length of wire connect
the two end pins of I/0 socket #5. This will connect the #5 chip select line
to UD3. When connecting the wire route it around the PC support on the bottom
of the board to prevent it from being cut. Re-install the mother board when
finished.
( ) The disk controller board should now be plugged onto I/0 slot 6 on the
computer's mother board.
( ) Connect the ribbon cable to the connector on the controller board. If the
connector supplied on the cable does not have an indexing pin install the
connector so that the cable runs toward the back of the board.
SWTPC 6800 Computer System Mother Board
( ) This completes the interconnection of the MF-68 and the computer system. The
disk system is now ready for checkout.

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Checkout and Use
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.
( ) Power up the MF-68 unit. Nothing should happen at this point.
( ) Power up the computer system. At this time the drive's heads will be stepped
to the TRACK 0 position (if not already there) and the DRIVE 0 head load LED
should come on.
( ) Load the small boot program into memory.
( ) Write protect the supplied diskette by placing a small piece of tape around
the square notch on the side of the diskette.
( ) Install the diskette into DRIVE 0 so that the write protect notch is at the
bottom. Be sure to close the door on the drive.
( ) Set the computer's program counter to 0100 and type G. Both drives should
start up and the operating system contained on the diskette should be loaded
into memory. If everything is operational the computer should respond with
SWTPC READY. At this point you are in the disk operating system. If the
system does not boot up correctly reset the program counter to 0100 and again
type G. If, after several tries, the computer fails to respond with ready
then the system is not operating properly. If this is the case refer to the
In Case of Problems section.
Using the Disk System
The ME-68 Minifloppy Disk System is designed to be as straightforward and
easy to use as possible. There are certain things that the user must be aware of,
however, for correct operation.
All memory in the system (16K minimum) must be operational for the disk to
operate properly. If any doubt exists run the ROBIT, MEMCON and CDAT diagnostics to
verify correct operation.
Diskettes should always be inserted with the WRITE PROTECT notch nearest the
LED's on the drive and with the label outward. Having this notch closed with a
piece of tape will prevent the disk from being written on. Leaving the notch open
will allow write privileges.
The LED's on the drives are head load lights and are activated only when the
head for a particular drive is loaded on a diskette. They are not power indicators.

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The disk controller has been designed to load the head and turn on the drive
motors only when necessary. When the computer requests data from the disk the
motors will activate and the correct head will load. After the information has been
retrieved the head will un-load, and after approximately 20-30 seconds, the motors
will turn off. During this off state it is normal for the DRIVE 0 LED to be
activated.
Just like cassette tapes, diskettes are made of magnetic materials and can be
erased by stray magnetic fields. Also, it is an excellent idea to back-up all
important disks on a spare diskette. The following precautions should be followed
concerning diskettes:
1. Return the diskette to its storage envelope whenever it is removed from a
drive.
2. Keep diskettes away from magnetic fields and from ferromagnetic materials
which might become magnetized. Strung magnetic fields can distort recorded
data on the disk.
3. Replace storage envelopes when they become worn, cracked or distorted.
Envelopes are designed to protect the disk.
4. Do not write on the plastic jacket with a lead pencil or ball-point pen. Use
a felt tip pen.
5. Heat and contamination from a carelessly dropped ash can damage the disk.
6. Do not expose diskette to heat or sunlight.
7. 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
interface will work correctly on slot 5 with DOS.

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Parts List - DC-1 Disk Controller
Resistors
____ R1 4.7K Ω1/4 watt resistor
____ R2 1M Ω1/4 watt resistor
____ R3 750K Ω1/4 watt resistor
____ R4 150 Ω1/4 watt resistor
____ R5 150 Ω1/4 watt resistor
____ R6 150 Ω1/4 watt resistor
____ R7 150 Ω1/4 watt resistor
____ R8 4.7K Ω1/4 watt resistor
____ R9 4.7K Ω1/4 watt resistor
____ R10 680 Ω1/4 watt resistor
____ R11 100 Ω1/4 watt resistor
____ R12 4.7M Ω1/4 watt resistor
____ R13 1K Ω1/4 watt resistor
Capacitors
____ C1 0.01 uF disc capacitor
____ C2 0.01 uF disc capacitor
____ C3 0.01 uF disc capacitor
____ C4 0.1 uF disc capacitor
____ C5 0.1 uF disc capacitor
____ C6 20 pF disc capacitor
____ C7 0.1 uF disc capacitor
____ *C8 100 uF @ 16 volt electrolytic capacitor
____ C9 0.1 uF disc capacitor
____ *C10 22 uF @ 6.3v tantalum capacitor
____ C11 0.1 uF disc capacitor
____ C12 0.1 uF disc capacitor
Semiconductors
____ *D1 1N4733 5.1 v zener diode
____ *D2 1N4742 12 v zener diode
____ *Ql SS 1122 silicon transistor
Integrated Circuits
____ *IC1 1771 Disk controller (MOS)
____ *IC2 555 timer
____ *IC3 555 timer
____ *IC4 7407 open collector hex buffer
____ *IC5 74LS139 Dual 2 to 4 decoder
*IC6 DM8097/74367 hex bus driver
____ *IC7 7406 open collector hex inverter
____ *IC8 74175 Quad D flip-flop
____ *IC9 DM8835 Quad bi-directional transceiver
____ *IC10 DM8835 Quad bi-directional transceiver
____ *IC11 74LS00 Quad 2 input NAND gate
____ *IC12 4049 (MOS) Hex inverter
____ *IC13 7805 5 volt regulator
Misc.
____ Y1 1MHz Crystal

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P-200 MF Power Supply
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
+ 5 VDC + 5% @ 3.0 amps
The power supply consists of the 3 1/8" W X 3 3/8" L X 3 3/4" H power
transformer, two large 2" diameter filter capacitors, 3 1/4" W X 4" L circuit board
and three regulator transistors. The design utilizes integrated regulators for
adjustment free outputs and built-in overload protection. The power supply may be
operated from 120 or 240 VAC, 50 to 60 Hz power systems.
PC Board Construction
( ) Clean the copper foil side of the circuit board with a piece of Scotchbrite®
(available at most hardware stores) to remove any oxidation.
( ) Attach all of the resistors to the circuit board. Use the parts list and the
component layout drawing to locate the proper position for each part. As with
all components unless otherwise noted, mount each flush with the top of the
board, bend the leads parallel to the board on the foil side and trim so that
1/16" to 1/8" of wire remains. Solder.
( ) Attach all of the diodes to the circuit board. Be sure the banded end of each
diode matches with the outline shown in the component layout drawing.
( ) Using some #18 gauge buss wire install jumpers in the two locations indicated
with the number "12". Solder. Make sure NO jumper is installed in the "24"
position. Use the component layout drawing for reference.
( ) Attach the twelve pin Wafercon connector to the circuit board. Be sure to
orient the connector as shown in the component layout drawing. Solder.
( ) Complete the first half of steps 1 thru 12 of the wiring table. Cut each wire
to the specified length and attach and solder it to the specified point on
the circuit board from the top side. Do not connect the other ends of the
wires to their destination terminations yet.
( ) This completes the circuit board assembly. Check to make sure that all
connections have been soldered and that there are no cold solder joints. Also
make sure that all components have been installed correctly as called for in
the instructions. Take note that there are many power supply components not
used in the P-20OMF version of the kit. Install only those components listed
in the parts list.

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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. Use the connector reference sheet contained within this instruction set
if you have any problem distinguishing between the connector pins. Do NOT insert
the connector pins into the connector shell until told to do so later in the
instructions.
Transformer Secondary Wire Connector pin Gender Connector Pin 4t
yellow female 1
green-white female 2
green-yellow male 3
green female 4
blue-white male 7
brown female 9
blue female 10
blue female 11
brown male 12
( ) Take note that the back side of the male connector shell is numbered. Using
the previous table, carefully insert each of the specified connector pins
into the correct numerical position of the connector shell. Insert the pins
from the back or numbered side of the connector and be careful not to make a
mistake. The pins cannot be removed without destroying them once they have
been pressed into place. This completes the transformer connector assembly.
Power Supply onto chassis assembly
( ) Snap the four nylon printed circuit board mounts onto the chassis in the
positions corresponding to the mounting holes on the circuit board.
( ) Attach the clamps for electrolytic capacitors C3 and C4 to the chassis using
#6-32 X 1/4" screws, lockwashers and nuts. Orient the clamps as shown in the
chassis pictorial. Leave the mounting screws loose until the capacitors have
been installed as called for later in the instructions. Attach a ground lug
under the C4 capacitor clamp screw nearest the front of the chassis.
( ) Attach lug strip LS-1 to the chassis using a #6-32 X 1/4" screw, lockwasher
and nut. Orient the lug strip as shown in the chassis pictorial
( ) Attach fuseholder F1 to the chassis with a #6-32 x 3/8 screw, lockwasher and
nut. Orient the fuseholder as shown in the chassis pictorial.
( ) Using a pair of pliers crimp the strain relief onto the line cord at a point
about 8" from the end of the line cord and insert the compressed strain
relief and line cord assembly into the 1/2" hole provided on the rear of the
chassis from the outside of the chassis, then release.
( ) Now insert electrolytic capacitors C3 and C4 into their clamps. Use the parts
list and chassis pictorial to determine position and orientation. Install
them exactly as shown in the pictorial. These capacitors are polarized so the
+ terminal must be positioned as shown in the drawings. Secure the capacitors
with #6-32 X 1/2" screws, lockwashers and nuts.

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( ) 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. Use the chassis pictorial to show proper orientation.
( ) Orient the power transformer so the nine wire secondary side is nearer the
left side of the chassis and secure with four #8-32 X 3/8" screws,
flatwashers and nuts.
( ) Remove the precoated insulators from their packages and place over the pins
on the bottom of regulator transistors Q3, Q4, and Q5.
( ) Install transistors Q3,Q4 and Q5 onto the chassis in the appropriate set of
holes from the outside of the chassis. Be sure you have put the right
transistor in the right set of holes. Secure each transistor with #6-32 X
3/8" screws, insulated shoulder washers, ground lugs and nuts. NOTE: The case
of each power transistor is electrically a transistor junction and hence must
be electrically isolated from all other electrical junctions including the
chassis. The mounting screws are electrically connected to each transistor
case and you must be sure, the screws do not contact the chassis as they pass
through. Keep in mind also that the wire leads of each power transistor must
be centered in the large holes through which they pass. The mounting screws
must be tightened evenly and with enough pressure to slightly compress the
transistor insulators. The entire bottom of the transistor case must be in
solid contact with the insulator for good heat transfer.
( ) Orient the printed circuit board as shown in the chassis pictorial and snap
it onto its mounts.
( ) For American standard 120 VAC line operation complete steps 13 thru 16 of the
wiring table. For European standard 240 VAC operation complete steps 17 thru
20 of the wiring table.
( ) Now go back and complete the second half of wiring steps 1 thru 12. When
attaching the wires to the regulator transistors Q3, Q4 and Q5, slip a 1"
piece of heat shrinkable tubing over each of the wires to be attached first.
Solder the wire directly to the transistor pin, slip the heat shrinkable
tubing over the exposed connection and shrink the tubing with the heat from
your soldering iron.
( ) Complete wiring steps 21 thru 35 of the wiring table. Wiring steps 11, 12 and
30 thru 35 require that the female connector pins be snapped into the
specified connector shell. Be very careful not to interchange the wires and
follow the precautions given for the transformer connector.
( ) Go back and double check all wiring steps and solder connections for
correctness and completion. Even a simple mistake can cause costly damage to
your power supply.
( ) Plug the twelve pin male connector attached to the power transformer's
secondary leads onto the twelve pin receptacle on the power supply printed
circuit board. Be sure to orient the connector correctly. It will fit only
one way.
( ) Install fuse F1 into the fuseholder.

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
ON.
( ) Using the metal chassis as a ground reference measure the following voltages
on the two power connectors listed below. If you find that any of the
voltages do not measure as specified, immediately remove power and recheck
all wiring and solder connections.
Connectors JO and J1
Pin # Voltage Tolerance
1 +12 VDC +5%
2 0 VDC +5%
3 0 VDC +5%
4 + 5 VDC +5%
( ) If everything checks out as called for then remove power, unplug the unit and
go back to the main disk assembly instructions for final assembly and
checkout. Once you are convinced that the power supply is working as it
should be use the wire ties supplied with;-the kit to bundle the wires where
necessary.

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Parts List P-200 MF Power Supply
Resistors
____ R1 240 ohm 1% resistor or 243 ohm 1%
____ R2 2030 ohm 1% resistor or 2000 ohm 1%
____ R3 240 ohm 1% resistor or 243 ohm 1%
____ R4 2030 ohm 1% resistor or 2000 ohm 1%
Diodes
____ D1* 1N5402 high current diode
____ D2* 1N5402 high current diode
____ D3* 1N5402 high current diode
____ D4* 1N5402 high current diode
____ D5* 1N4003 diode
____ D6* 1N4003 diode
____ D7* 1N5402 high current diode
____ D8* 1N5402 high current diode
____ D9* 1N5402 high current diode
____ D10 1N5402 high current diode
____ D11* 1N4003 diode
Capacitors
____ C3* 20,000 mfd @ 25 VDC electrolytic capacitor
____ C4* 29,000 mfd @ 15 VDC electrolytic capacitor
Regulators
____ Q3* LM323 +5 VDC regulator
____ Q4* LM317 adjustable regulator
____ Q5* LM317 adjustable regulator
Misc.
____ T1* Power transformer 50-60 Hz
Primary: 120/240 VAC
Secondaries: 12 VAC @ 1.5 amp
12 VAC @ 1.5 amp
7 VAC @ 3 amp
24 VAC @ 200 ma
____ F1 2 1/2 amp slo-blo fuse
All components flagged with a (*) must be oriented as shown in the component
layout drawing and pictorials.

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WIRE FROM TO
STEP LENGTH GAUGE PART TERMINAL SOLDER PART TERMINAL SOLDER
1 8 1/2 ” #18 PC board A yes C3 lug (+) yes
2 7" #18 PC board B yes Q4 B3 yes
3 6 1/2" #18 PC board C yes Q4 Bl yes
4 9" #18 PC board D yes Q5 C3 yes
5 8" #18 PC board E yes Q5 C1 yes
6 9" #18 PC board F yes C4 lug (+) yes
7 11” #18 PC board G1 yes C3 lug (-) yes
8 9" #18 PC board G2 yes C4 lug (-) yes
9 9" #18 PC board G3 yes C4 lug (-) yes
10 10"' #18 PC board +5 yes Q3 A2 yes
11 17” #18 PC board +5 yes female pin J0 #4 yes
12 20” #18 PC board +5 yes female pin J1 #4 yes
120 VAC OPERATION
13 5" - T1 Black - LS-1 A no
14 5" - T1 White - LS-1 A no
15 5" - T1 Blk-Wht - F1 A no
16 5" - T1 Blk-Red - Fl A yes
240 VAC OPERATION
17 5” - T1 Black - LS-1 A no
18 5” - T1 White - LS-1 C no
19 5” - T1 Blk-Red - LS-1 C yes
20 5” - T1 Blk-Wht - F1 A yes
21 - - line cord A - LS-1 A yes
22 - - line cord B - S1 A yes
23 10” #18 S1 B yes F1 B yes
24 4" #18 C3 lug (-) yes C4 lug (-) yes
25 9" #18 C4 lug (-) yes Q3 A4 yes
26 10" #18 C4 lug (+) yes Q3 A1 yes
27 11 1/2" #18 C3 lug (+) yes Q4 B2 yes
28 13 1/2" #18 C3 lug (+) yes Q5 C2 yes
29 8" #18 C3 lug (-) yes Gnd lug - yes
30 18" #18 C3 lug (-) yes female pin J0 #3 yes
31 15” #18 C3 lug (-) yes female pin Jl #3 yes
32 18” #18 C4 lug (-) yes female pin J0 #2 yes
33 15" #18 J1 #2 yes
34 18 1/2" #18 Q4 g4 yes female pin J0 #1 yes
35 17" #18 Q5 C4 yes female pin J1 #l yes

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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. Using the printed pattern as a guide look over the board for
solder bridges. Accidental solder bridges are the second most common problem in
kits that are returned for repair. Be sure that all jumpers called for are in place
and that all connections have been soldered.
If you suspect that the "Shugart" SA-400 drive unit itself is not working
properly, remove the drive and return it to us for testing. Do not attempt to
adjust, or repair the drive unit. Special equipment and tools are required and
considerable damage can be done by attempting to work on these units without proper
training.
REPAIR SERVICE
If you have a problem that you cannot solve, the kit may be returned for
factory service. Please return the entire* kit (Chassis, case, PC boards, cable,
drives, etc.) Be sure to include the supplied diskette containing FDOS.
*Remove the power transformer. This reduces postal costs and damage. Selected
individual boards may be returned but in most cases it is best to send the entire
unit. Do not remove the boards from the drives themselves and send them in. Repairs
are performed for a flat labor charge per board plus parts and postage.
CIRCUIT Labor Charge
Controller board and cable $16.00
Power supply $10.00
Disk drives Depends on individual drive
If we find that the board, drive or complete unit is functional as received
and does not require service, the Checkout Charge is $10.00.
A confirmation sheet will be sent upon receipt of the kit. Please do not ask
for an estimate or a detailed report on exactly what was done in repairing your
unit as we cannot provide this service.
It is not necessary to enclose any funds with the kit, you will be billed for
authorized repairs.
ADDITIONAL DISKETTES
Additional diskettes are available at $5.50 ea. Part # FD-M

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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.
Ship prepaid by UPS or insured Parcel Post. We cannot pick up repairs sent by
bus.
Ship to: Southwest Technical Products Corp.
Repair Department - Digital Group
219 W. Rhapsody
San Antonio, Texas 78216

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