SWTPC DC-4 User manual

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SWTPC Minifloppy Disk Unit
Introduction
The SWTPC minifloppy disk unit is a dual drive, double sided, five-inch disk
unit. Double density operation is also available when using the DC-4 disk
controller board. The disk unit was designed specifically for the SWTPC 6809
computer. Although the disk unit was completely assembled and tested at the
factory, minor reprogramming of the circuit board may be necessary to operate with
your particular computer system. It is suggested that this instruction manual be
read completely before attempting to use the unit.
Jumper Programming the DC-4 Controller Board
There are five Jumper blocks on the DC-4 controller board that must be
properly programmed before the board is installed in the computer. Programming is
achieved by plugging the small plastic blocks onto the specified set of programming
pins.
( ) There are two Jumper locations near the bottom of the board marked 4/16. This
Jumper selects the number of address locations assigned to each I/0 port. If
your computer uses the earlier MP-B or MP-B2 motherboard, RESET switch on
RIGHT side of chassis, put the Jumpers in the 4 position. All other computer
installations should have the Jumpers in the 16 position.
( ) If you will be using the disk unit with a 6800 (not 6809) processor board or a
6809 using FLEX 2.5 or earlier, install the Jumper in the 00 position. All
other installations should have the Jumper in the 09 position.
( ) Unless specifically noted with a particular piece of software, both the IRQ
and FIRQ Jumpers should be in the NORM (OFF) positions or removed completely.
Interrupts are presently not used with this board.
Scanned and edited by Michael Holley Oct 23, 2000 [email protected]
Southwest Technical Products Corporation Document Circa 1978

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Installation
( ) In order for the MF-69 to work properly with an SWTPC 6800 or 6809 computer
with an MP-B or MP-B2 (not MP-B3 or MP-MB) motherboard, one minor
modification needs to be made to the motherboard. With a short length of wire
connect together each of the two end pins of 30-pin I/0 connector row #5.
This will connect the #5 port 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 pinched. Re-install the motherboard when finished. This modification
should be done only on MP-B or MP-B2 motherboards.
( ) The disk controller board should now be plugged on to !/0 slot 6 on computers
with MP-B or MP-B2 motherboards or I/0 slot 1 on computers with MP-MB or
MP-B3 motherboards. The lower edge of the controller board may need to be
notched slightly for insertion in certain older chassis.
( ) Connect the ribbon cable to the connector on the controller board. Route the
cable thru a hole in the rear of the computer or as desired. If the connector
supplied on the cable does not have an indexing pin, install the connector so
that the cable extends toward the back of the board. The pin 1 side should be
nearer the front edge of the board when installed in the computer. When the
controller board utilizes a connector that faces the rear of the computer,
connect the cable such that the pin 1 side of the cable (banded side) goes
toward the 1 marked on the rear mounting panel (toward the top of the
computer).
( ) Double check to be sure the cable is installed securely on the drives. All
cables should be installed as in the following pictorial. By running the
cable through the hole in the rear of the chassis the only natural way for
the connectors to fit will be the right way, as shown. Be very careful that
the cable is installed correctly--incorrect installation can cause damage to
the controller and the drives.

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( ) This completes the interconnection of the disk and the computer. The disk
unit is now ready for checkout/
Checkout and Use
( ) Be sure that your computer contains enough memory to run the disk operating
system that you are using. The software manual supplied with the diskette
should specify the amount of memory required.
( ) After connecting the disk unit is ready for use. If at any time the disk
fails to operate as described, power down the system and recheck all
assembly.
( ) Power up the disk unit and computer. The power switch for the disk unit is on
the back panel. The switch is ON when the paddle on the switch is toward the
right as viewed from the front.
( ) Write protect the system diskette by placing a small piece of tape around the
square notch on the side of the diskette.
( ) This completes the interconnection of the disk and the computer. The disk
unit is now ready for checkout.

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( ) Install the diskette into DRIVE 0 (left drive) so that the write protect
notch is at the bottom. Be sure to close the door on the drive.
( ) Type in the minifloppy disk boot character on your terminal. Check your
computer's monitor documentation for the correct character. If the disk unit
does not respond, recheck each step of this instruction set then refer to the
IN CASE OF PROBLEMS section - of this manual.
Using the Disk Unit
The minifloppy disk unit 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 computer must be operational for the disk to operate
properly. If any doubt exists, run the memory diagnostics to verify correct
operation.
Diskettes should always be inserted with We 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 upon. Leaving the notch open
will allow write privileges.
The LED indicators on the front of the drives are drive select lights and are
activated only when the particular drive is selected. They are not power
indicators.
The disk controller has been designed to select the drive and turn on the
drive motors only when necessary. When the computer requests data from the disk,
the motors will activate and the correct drive will select. After the information
has been retrieved the drive will deselect, and after approximately one minute the
motors will turn off.
NOTE: Some versions of the disk operating system will keep a drive selected
after an operation is finished. This is a normal condition.
Just like cassette tapes, diskettes are made of magnetic materials and can be
era 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. Strong 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.

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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 ................diskettes to excessive heat or sunlight.
7. Do not touch or attempt to clean the disk surface. Abrasions may cause loss
of stored data.
With MP-B and MP-B2 motherboards the disk unit 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.
IMPORTANT: Do not power the computer or disk units on or off while diskette
are installed in the drives with the doors closed. Doing so may destroy any or all
the data stored on the diskette(s).
IN CASE OF PROBLEMS
If your disk unit fails to operate properly we suggest that you first go back
and double check all programming and installation steps. An improperly installed or
incorrectly programmed board can cause anything from intermittent operation to no
operation at all. Also if your system diskette has been damaged the unit will not
function properly. If the drive 0 select light does not come on and/or the drive
motors do not start, then a hardware problem should be suspected. Service of the
minifloppy disk unit should be left to competent technical personnel.

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Factory Exchange Service Plan for Assembled Units Only
Southwest Technical Products Corp. provides an exchange program for factory
assembled products and product subassemblies which require service. The plan is
designed to provide a way of returning systems to operational status as quickly as
possible.
All equipment is registered in the plan for a period of six months after
installation. After this time an exchange charge is made, if the equipment has not
been placed under service contract.
Any article to be returned to the factory must be properly packed and marked
with a return address. This should include the name and telephone number of the
person requesting the repair. The nature of the problem should also be described as
fully as possible.
The serial number of the system from which any subassembly was removed must
be supplied with the returned subassembly.
Ship all articles to be returned to the factory prepaid by UPS or insured
parcel post. We cannot pick up repairs sent by bus. No COD shipments can be
accepted. Articles will be returned prepaid. Upon receipt of a repairable,
defective article and payment covering the cost of the article exchange, Southwest
Technical Products Corp. will ship a new or equivalent-to-new performance exchange
article.
Exchange articles will be placed under a six-month exchange plan at no
additional cost, just as new equipment.
EXCHANGE CHARGES
DC-4 Controller board and cable ............$40.00
Power supply ............................... 20.00
Disk drive ........... depends on individual drive
Ship to: Southwest Technical Products Corporation
Repair Dept. - Digital Group
219 W. Rhapsody
San Antonio, Texas 78216

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Drive Programming'
Drive programming on assembled units has been done at the factory. The
following is supplied for the convenience of technical personnel.
Programming Shugart, Siemans or Wangco 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.
( ) At the bottom left corner of the board you will notice what looks 1ike an IC
made up jumpers in a socket. On one of the drives remove the jumper block
with a screwdriver and bend upward (straight) the pins that go to terminals
DS2, DS3 and MX. Do not break these pins off. Reinstall 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. This drive is now programmed as DRIVE 0.
( ) On the other drive, bend straight out the pins going to DS1, DS3 and MX.
Re-install the jumper so that HS, DS2 and the unlabeled pin have jumper pins
installed.
( ) 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 1.

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Programming Qume Drives
( ) 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 screwdriver and bend upward (straight) the pins that go to terminals
DS1, DS2, MX, DS3 and HM. Do not break these pins off. Reinstall the Jumper
block into the socket. As a double check, the Jumper block should have pins
inserted only in terminals DSO and HS. This drive is now programmed as DRIVE
0.
( ) On the other drive, bend straight out the pins going to DSO, DS2, MX, DS3 and
HM. Re-install the Jumper so that HS and DS1 pins have Jumper pins installed.
( ) 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 re-installed. This drive is now programmed as DRIVE 1.

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Programming Tandon Disk Drives
Carefully remove both drives from their boxes an turn the drives so that the
edge connectors are nearest you and so that the belt and pulleys are on the bottom.
( ) 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 screwdriver and bend straight (upward) the pins shown below. Do not
break these pins off. Re-install the jumper block as shown. This drive is now
programmed as DRIVE 0.
( ) On the other drive, bend straight out the pins of its jumper block as shown
below. Re-install it as shown.
( ) Located on this drive below and to the right of the jumper block you will
notice what appears to be an IC in a socket. This is an array of pull-up
resistors and should be removed. This drive is now programmed as DRIVE 1.

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Parts List -- DC-4 Minifloppy Disk Controller
Resistors
____ R1 10K ohm 1/4 watt resistor ____ R10 150K ohm 1/4 watt resistor
____ R2 56K ohm " ____ R11 4.7M ohm " "
____ R3 75K ohm " ____ R12 33 ohm "
____ R4 150 ohm " ____ R13 47K ohm "
____ R5 150 ohm " ____ R14 47K ohm "
____ R6 150 ohm " ____ R15 100K ohm potentiometer
____ R7 150 ohm " ____ R16 50K ohm potentiometer
____ R8 10K ohm " ____ R17 10K ohm 1/4 watt resistor
____ R9 100K ohm " ____ R18 10K ohm
Capacitors
____ *C1 4.7 mfd tantalum
electrolytic capacitor ____ *C11 1 mfd electrolytic capacitor
____ *C2 4.7 mfd tantalum
electrolytic capacitor ____ C12 0.1 mfd capacitor
____ C3 0.1 mfd capacitor ____ C13 100 pfd capacitor
____ C4 0.1 mfd capacitor ____ C14 0.1 mfd Capacitor
____ C5 0.1 mfd capacitor ____ C15 0.1 mfd Capacitor
____ C6 20 pfd capacitor ____ C16 0.01 mfd film capacitor
____ C7 0.1 mfd capacitor ____ C17 0.33 mfd tantalum
capacitor
____ *C8 220 mfd @10 VDC
electrolytic capacitor ____ C18 56 pfd poly capacitor
____ C9 0.1 mfd capacitor
electrolytic capacitor ____ C19 0.1 mfd capacitor
____ C10 0.01 mfd film capacitor
0.02 ____ C20 0.1 mfd capacitor
Integrated Circuits
____ *IC1 1797 disk controller (MOS) ____ *IC9 74LS244 octal buffer
____ *IC2 14541 timer (MOS) ____ *IC10 74LS32 quad OR gate
____ *IC3 74LS123 dual one shot ____ *IC11 74LS132 quad 2 input NAND
gate
____ *IC4 74LS244 octal buffer ____ *IC12 4049 hex inverter (MOS)
____ *IC5 74LS139 dual 2 to 4
decoder ____ *IC13 7805 5-volt regulator
____ *IC6 74LS124 VCO ____ *IC14 78L12 12-volt regulator
____ *IC7 74LS240 octal inverter ____ *IC15 1691 Data separator
____ *IC8 74LS175 quad D-flop ____
Miscellaneous
____ Y1 1.0 MHz crystal
2.0
* All components flagged with a * must be oriented as shown in the component
layout drawing.

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Data Separator Adjustment Procedure - DC-4 Disk Controller
Adjustment of the data separator on the DC-4 disk controller board requires
some special equipment, such as a good oscilloscope. This adjustment requires some
technical ability and should only be done by qualified personnel. This adjustment
has been performed at the factory on assembled units.
1.) Connect the oscilloscope to test point 1 (TP 1) on the DC-4 board. The ground
lead of the scope should be connected to the ground screw on the regulator or
other ground on the DC-4 board, not on the ground pin of the connector bus.
2.) Adjust potentiometer R15 to obtain a 1.4 volt DC reading. This reading can be
verified using a good high impedance DC voltmeter.
3.) Connect the oscilloscope to test point 2 (TP 2) on the DC-4 board. Adjust
potentiometer R16 for a 2.0 MHz square wave. This measurement can be verified
with a good frequency counter.
4.) After correct operation of the board is verified, secure each of the
potentiometers by using liquid 'silicon rubber cement or equivalent. Do not
pour an epoxy or cyanoacrylate type glues down inside the potentiometer as
these could ruin the part.

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Parts List P-30 MF Rower Supply
Resistors Diodes
____ R1 243 ohm 1% resistor ____ D1* 1N5402 high current diode
____ R2 2030 ohm 1% resistor ____ D2* 1N5402 high current diode
____ R3 243 ohm 1% resistor ____ D3* 1N5402 high current diode
____ R4 2030 ohm 1% resistor ____ D4* 1N5402 high current diode
____ D5* 1N4003 diode
____ D6* 1N4003 diode
Capacitors ____ D7* 1N5402 high current diode
____ C1 0.1 mfd capacitor ____ D8* 1N5402 high current diode
____ C2 0.1 mfd capacitor ____ D9* 1N5402 high current diode
____ C3* 20,000 mfd @ 25 VDC
electrolytic capacitor ____ D10* 1N5402 high current diode
____ C4* 29,000 mfd @ 25 VDC
electrolytic capacitor ____ D11* 1N4003 diode
____ C5 not used ____ D12 not used
____ C6 not used ____ D14 not used
____ D15 not used
Regulators
____ Q1* LM323 +5 VDC regulator ____ Q3* LM317 adjustable regulator
____ Q2* LM317 adjustable regulator ____ Q4 not used
Miscellaneous
____ T1* Power transformer 50-60 Hz ____ Q3* 2 1/2 amp slo-blo fuse
Primary: 120/240 VAC ____ J1 jumper installed
Secondaries:l2 VAC @1.5 A
12 VAC @1.5 A
7 VAC @3A
24 VAC @200 mA
____ J2 jumper installed
All components flagged with a (*) must be oriented as shown in the component
layout drawing and pictorials.

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