NorthStar Horizon User manual

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2M7 Ninth Street
Berkeley, Co,
94710
Horizon Computer System
Double Density
Copyright ©1978, Nor1'h Star Computers, Inc,
HRZ·D·DOC
Revision 1

INTROD~CTION
The North Star Computers HORIZON™ is a high-performance, Z80A
based microcomputer system which is especially suited for
business, educational, and software development applications. It
features fast-access disk storage as an integral part of the
package, 4 MHz microprocessor operation, and built-in I/O
capability. The HORIZON uses the S-100 bus structure, allowing a
large selection of compatible products. The system will support
up to 4 disk drives, allowing up to 716K bytes of on-line disk
storage. Powerful system software, including North Star Disk
BASIC, Disk Operating System, and Monitor program, are provided
on diskette with disk versions of the HORIZON. The HORIZON is
compatible with nearly all programs previously written for 8080
or Z80 based machines. North Star BASIC programs which run on
the North Star MICRO-DISK SYSTEM will also run on the HORIZON. A
list of the growing number of HORIZON-compatible applications
programs is included in the North Star Newsletter, which you will
receive after filling out and returning vour Warranty Card.
If you have purchased your HORIZON as a kit, then skim this
manual completely once, and then carefully follow the
instructions in sequence. Be sure to read the Assembly
Information section, even if you are an experienced kit builder.
If you have purchased an assembled HORIZON, be sure to read the
Using the Serial Interfaces section for instructions on
connecting a terminal. You need only read the assembly and
checkout sections for a more complete understanding of how your
computer is built. Of course, if you plan to maintain the
HORIZON yourself, the checkout steps will be very important.
It is important for every HORIZON user to be familiar with the
Operation and Maintenance section, and all sections of this
manual and the accompanying manuals describing the North Star
software. There is a lot of material presented here, but you
will obtain far more performance from your computer if you take
the time to read about all of its capabilities. The HORIZON
documentation includes:
HORIZON Computer System Manual
North Star Z80A Processor Board Manual
North Star 16K RAM Board Manual
North Star System Software Manual
SA-400 minifloppy OEM Manual
Z80 Technical Manual

TABLE OF CONTENTS
Introduction
I. GENERAL INFORMATION
Limited Hardware Warranty
Limited Software Warranty
Cautions
Software License
II PARTS LISTS
Chassis .
Power Supply
Universal Power Supply Option
Motherboard
Wood Cover
Metal Cover
Second Serial Interface Option
Parallel I/O Interface Option
Disk Subsystem (MDS-H)
Second Disk Drive.
III. ASSEMBLY AND CHECKOUT
5
5
6
6
7
8
8
9
10
10
11
11
12
13
Assembly Information 14
Figure lA: Identification of Components 17
Figure IS: Identification of Sheet Metal Parts 18
Power Supply Assembly 19
Table 1. Power Supply Wires 25
Figures IP,2P,lC, 10 27
Motherboard Assembly 28
Second Serial Interface Option Assembly 34
Parallel I/O Interface Option Assembly 36
Disk Drive #1 Power Regulation Assembly 37
Disk Drive #2 Power Regulation and Cable Assembly 38
Chassis Assembly 40
Figure lC: Top view of Assembled HORIZON-l 44
Processor Board Assembly 45
RAM Board Assembly 45
Disk Controller Board Assembly 46
Disk Controller Board Checkout 50
Integrated System Chec~out 54

TABLE OF CONTENTS (Cont.)
IV. DETAILED INFORMATION
Disk Controller Theory of Operation .
Disk Controller Configuration Options
Disk Drive Configuration
Motherboard Theory of Operation
Motherboard I/O Port Addressing
Using the Serial I/O Interfaces
using the Parallel I/O Interface
using [he Real-Time Clock
Motherboard Interrupts
HORIZON Grounding .
V. OPERATION AND MAINTENANCE
Operation
Diskettes
Maintenance
Troubleshooting
Out of Warranty Repair
VI. APPENDICES
1. Pulse Signal Detection
2. Disk Controller Schematic Drawing
3. Motherboard Schematic Drawing
57
65
66
67
71
72
76
79
79
80
81
81
82
82
82
83
84
88

LIMITED HARDWARE WARRANTY
North Star Computers, Inc. warrants the electrical and mechanical
parts and workmanship of this product to be free of defects tor a
?eriod of 90 days from date ot purchase. If such defects occur,
North Star Computers, Inc. will repair the defect at no cost to
the purchaser. This warranty does not extend to defects
resulting trom improper use or assembly by purchaser, nor does it
cover transportation to the factory. Also, the warranty is
invalid if all instructions included in the accompanying
documentation are not carefully followed. Any adjustment,
modification, or disassembly of any disk drive unit will void the
warranty on that disk drive unit. Should a unit returned for
warranty repair be deemed by North Star Computers, Inc. to be
defective due to purchaser's action, then a repair charge not to
exceed $30 without purchaser's consent will be assessed. ANY
UNIT OR PART RETURNED FOR WARRANTY REPAIR MUST BE ACCOMPANIED BY
ACOpy OF THE ORIGINAL SALES RECEIPT. This warranty applies to
units located outside the United States of America only if all
costs and arrangements for.transportation of the product to and
from the factory are borne entirely by the customer. This
limited warranty is made in lieu of all otner warranties,
expressed or implied, and is limited to the repair or replacement
of the product. No warranty, expressed or implied, is extended
concerning the completeness, correctness, or suitability of the
North Star equipment for any particular application. There are
no warranties which extend beyond those expressly stated herein.
LI~ITED SOFTWARE WARRANTY
The following limited warranty applies to the North Star BASIC,
DOS, and Monitor software delivered or diskette with the HORIZON
computer. North Star Computers, Inc. warrants that a copy
identical to the North Star master copy of the software has been
stored on the customer diskette and can be read into computer RAr~
memory from the diskette by a properly functioning HORIZON
computer using the Nortn Star disk controller board and disk
drive. If a diskette malfunctions and has not been damaged by
the customer and has not been operated with the write-protect tab
removed, then North Star will re-write or replace the diskette if
it is returned to North Star, prepaid, within three months from
date of purchase.
No warranty, expressed or implied, is extended concerning the
completeness, correctness, or suitability of the North Star
software for any particular application. No consequential damage
resulting from use of the software is covered - this warranty is
limited to the repair or replacement of the original software
diskette.
5 North Star HORIZON Computer

CAUTIONS
1. Correct this document from the errata sheets, if any, before
doing anythinq else.
2 . Assembly
project.
building
of this product as a kit is a complex, demanding
It should not be attempted without previous kit
experience.
3. Do NOT insert or remove any boards from the computer when the
power is on. Note that the power is not off until the front
panel power LED has completely dimmed.
4. Do NOT insert or remove IC's from any board whlle the power
is turned on. Note that the power is not off until the front
panel power LED has completely dimmed.
5. Be sure that all IC's are inserted in their correct positions
and with correct' orientation before turning on the power. Be
sure that all IC pins are inserted into the socket holes and
are not bent under the IC and are not outside the socket.
6. Do NOT connect or disconnect, mount or dismount, or any way
physically tamper with the disk drive(s) or any PC board
while the power is turned on.
7. Carefully observe the prescribed rules for handling the MOS
type integrated circuits and any PC board containing these
devices. The handling procedures are described in the
Assembly Information sectior.
8. To avoid the possibility of a severe shock, do NOT touch the
power supply section of the computer whenever the power cord
is plugged into an AC outlet.
SOFTWARE LICENSE
The North Star BASIC, DOS and Monitor are copyrighted products of
North Star Computers, Inc., and are included with the HORIZON
computer under the following license agreement:
The software maybe used in conJunction with the North Star
HORIZON computer and North Star MICRO-DISK SYSTEM only. The
customer may make copies of the software for convenience of use,
as long as the North Star copyr~ght notice is preserved with eacn
copy. This license specifically prohibits use of the software in
a computer which does NOT include a North Star disk controller
board, and also specifically prohibits modification of the
software for use in any system which does not contain a North
Slar disk controller board.
North Star HORIZON Computer
6

CHASSIS PARTS LIST
SHEET METAL
1
1
1
1
1
2
chassis frame
disk drive mounting bracket
chassis partition piece
front panel
back panel
cover mounting brackets
MISCELLANEOUS PARTS
1
1
6
4
2
1
9
9
12
12
HORIZON nameplate
serial number plate
plastic card guides
plastic cable ties
cable tie mounting brackets
power-on LED with leads
8-32 nuts
#8 lock washers
6-32x3/8" machine screws
#6 lock washers
ADDI TIONAL PART FOR BORI ZON-l ONLY
1
black plastic face plate
ADDITIONAL PARTS cOR HORIZON-0 ONLY
2
7
black plastic face plates
North Star HORIZON Computer

1
1
1
1
1
1
1
1
1
1
1
1
2
1
2
1
4
4
4
17
4
5
1
27
9
29
1
4
1
4
2
2
10
12
2
1
1
1
1
1
POWER SUPPLY PARTS LIST
transformer. Part No. HRZ-Tl
180,000uf 15 volt electrolytic capacitor
11,000uf 25 volt electrolytic capacitor
8,900uf 25 volt electrolytic capacitor
cool ing fan
cooling fan grill
line cord
line filter, Corcom 6EFl
fuseholder
5 amp normal blow fuse
power switch
bridge rectifier. IR 250JBIL
stud diodes, MRl120 (wires attached)
3" capacitor clamp
1 3/8" capacitor clam~s
stud diode" mounting bracket
1/4"x5/8" machine screws
1/4" lac k washer s
1/4" nuts
6-32x3/8" machine screws
6-32x7/8" machine screws
6-32xl/2" machine screws
6-32x5/8" machine screw
#6 lock washers
6-32 nuts
wires (see Table 1 for details)
wire label card
adhesive backed rubber feet
resE't switch
mica washers
#10 teflon spacers
#10 flat washers
lO-32x3/8" machine screws
#10 lock washers
10-32 nuts
UNIVERSAL POWER SUPPLY OPTION PARTS LIST
transformer. Part No. HRZ-TIS
(instead of HRZ-Tl)
2" jumper wire
3-terminal white Jumper wire
3-terminal black jumpE,r wire
2.5 amp fuse
North Star HORIZON Computer

MOTHERBOARD PARTS LIST
I~TEGRATED CIRCUITS
2
1
1
1
1
1
2
1
1
RoSISTORS
74LS03
74LS04
74LS05
74LS14
74 LS 74
74LS132
74LS136
74 LS 13 8
74LS139
2
3
1
1
1
1
1
1
74LS161
74LS241
74LS259
74LS393
1488
1489
4020(MOS)
8251(MOS)
3
2
1
2
1
1
1
2
2
1
1.2K
2.2K
4.7K
5.6K
lK
lK
560
220
330
100
1/4 wa tt 5%
1/4 watt 5%
1/4 watt 5%
1/4 watt 5%
1/2 watt
1/4 watt
1/4 watt 5%
1/4 watt 5%
2 watt
2 Watt
CAPACITORS
3
3
H
4
2.2uf dipped tantalum
6.8uf dipped tantalum
.047uf ceramic disc
470pf ceramic disc
R~GULATORS
1
1
1
5 volt, 7805 or 340t-5
12 volt. 78L12
-12 vol t, ,9L12
ESOCKETS
14
9
3
1
14-pin sockets
liS-pin sockets
20-pin sockets
28-pin sockets
MISCELLANEOUS PARTS
1
1
3
9
printed circuit board, HRZ-MB
transistor, 2N3904
16-pin DIP headers
North Star HORIZON Computer

3
1
1
3
9
2
11
11
1
2
2
2
1
4
4
1
4
14-pin DIP headers
heat sink, Thermalloy 60308
2S-pin connector
100-pin edge connectors
1/4" auick-connect lugs
3/16" auick-connect lugs
6-32x3/8" machine screws
#6 lock washers
6-32 nut
4-40x3/8" machine screws
#4 lock washers
4-40 nuts
WOOD COVER PARTS LIST
Vvood cover
6-32xl" brass machine screws
#6 brass flat washers
METAL COVER PARTS LIST
metal cover
6-32x3/8" machine screws
North Star HORIZON Computer
10

2
2
1
1
6
1
1
3
1
2
1
1
1
1
1
8
1
2
2
2
1
2
1
3
2
1
1
2
2
2
2
2
4
4
4
11
SECOND SERIAL INTERFACE OPTION (HRZ-SIO) PARTS LIST
1488 IC's
1489 IC's
8251 IC
transistor, 2N3904
14-pin IC sockets
16-pin IC sockets
28-pin IC socket
14-pin DIP headers
16-pin DIP header
5.6K resistors 1/4 Watt 5%
4.7K resistors 1/4 Watt 5%
lK resistor 1/4 Watt 5%
lK resistor 1/2 Watt
560 ohm resistor 1/4 Watt 5%
220 ohm resistor 1/4 Watt 5%
470pf ceramic disc capacitors
2S-pin connector'
4-40x3/8" machine screws
#4 lock washers
4--40 nuts
PARALLEL I/O INTERFACE OPTION (HRZ-PIO) PARTS LIST
74LS74 IC
74LS373 IC's
7437 IC
14-pin IC sockets
23-pin IC sockets
14-pin DIP header
2.2K resistor 1/4 Watt 5%
330 ohm [E3istors 1/4 Watt 5%
220 ohm resistors 1/4 Watt 5%
15-pin connectors
15-pin plugs
15-pin plug hood assemblies
4-40x3/8" machine screws
#4 lock washers
4-40 nuts
North Star HORIZON Computer

DISK SUB-SYSTEM (MDS-H) PARTS LIST
(included in HORIZON-l and HORIZON-2)
1
1
1
1
4
1
1
1
1
2
5
5
3
1
1
disk drive, Shugart SA-400 (double density)
18" ribbon cable
12 1/2" power cable
power plug
powe r pI uq pins
5 volt regulator, 7805 or 34GT-5
12 volt regulator, 7812K or 340K-12
heat sink, Thermalloy 6030B
heat sink, Thermalloy 6016B
.047 ceramic disc capacitors
6-32x3/8" machine screws
#6 lock washers
6-32 nuts
blank diskette
HORIZON s~ftware diskette
DISK CONTROLLER PARTS
1
5
19
22
1
1
6
2
1
2
2
2
2
printed circuit board (5" x 10"), MDS-AD
20-pin IC sockets
16-pin IC sockets
14-pin IC sockets
34-pin cable connector header
crystal, 4MHz
IN4148 diodes
+5 volt regulators, 7805 or 340T-5
+12 volt regulator, 78L12
heat sinks, 61G7B-14
6-32x3/8" machine screws
#6 lock washers
6-32 nuts
Integrated Circuits
2
1
1
1
2
1
6
3
3
1
4
1
1
74LS00
74 LS0 2
74LS08
74LSll
74LS14
74LS32
74LS74
74LS109
74LS123
74LS138
74LS161
74LS164
74LS174
3
2
1
1
3
1
3
1
1
1
1
1
1
74LS241
74LS253
74LS257
74LS273
74LS393
7404
7438
74166 or 74LS166
OWE PROM (6301 or 82S129)
DSEL PROM (6301 or 82S129)
DPGM PROM (6309)
LF356
3080
North Star HORIZON Computer
12

Capacitors
4
2.2uf tantalum
2
6.8uf
tantalum
1
.01uf dipped mylar
10%
~ .022uf
dipped mylar 10%
1
.047uf dipped mylar 10%
1
33pf dipped m1ca 5%
1
100pf dipped m1ca 5%
2
200pf dipped
mica 5%
,
330pf dipped mica
1%
1
470pf dipped mica
5%
1 47pf
ceramic disk
20 %
1
100pf ceramic disk
20%
1
330pf ceramic disk 20%
18
.047uf ceramic disk
Elesistors
1
3.3
ohm
1/4W 5% 3
5.6K ohm
1/4W
5%
:> 150 ohm 1/4W 5% 1 6.19K ohm
1/4W
1%
330 ohm
1/4W 5% 2
6.8K
ohm 1/4W 5%
'I
470 ohm 1/4W
5% 1
9.1K ohm
1/4W
5%
:~
680.
ohm
1/4W 5% 110K ohm 1/4W 5%
J
2.2K ohm 1/4W 5%
113K ohm 1/4W
5%
3.3K
ohm
1/4W 5%
115K ohm
1/4W
5%
3.6K
ohm
1/4W 5%
327K ohm
1/4W 5%
SECOND DISK DRIVE (HRZ-DRV) PARTS LIST
(included in HORIZON-2)
1
disk drive, Shugart SA-400
1 34-pin edge connector
1 12 1/2" power cable
1 power plug
4 power plug pins
1 5 volt regulator, 7805 or 340t-5
1 12 volt regulator, 7812K or 340K-12
1 heat sink, Thermalloy 6030B
1 heat sink, Thermalloy 6016B
2 .047 ceramic disc capacitors
5 6-32x3/8" machine screws
5#6 lock washers
3 6-32 nuts
13 North Star HORIZON Computer

ASSEMBLY INFORMATION
Read completely through each section before beginning the first
instruction step of that section. Perform all operations in the
sequence indicated. Read each step entirely, including any notes
that accompany the step, before beginning to follow the step.
WORK AREA AND TOOLS
Start with a clean, well-lit and well-ventilated area to work.
The area should be large enough to accommodate the kit, tools,
parts and assembly instructions. Suggested tools are:
screwdrivers, needle-nose pliers, diagonal cutters, soldering
iron, solder, and masking tape. A number of tests will require
using a VOM (ohmmeter-voltmeter), or VTVM. Also highly
desirable, but not necessary, are an IC inserter, a screw-holding
screwdriver, an oscilloscope or logic probe, and an extender
card. [Note that if you do not have an oscilloscope or logic
probe, waveforms can be detected by one of the procedures
described in Appendix 1.]
SOLDERING TIPS
For best results use a 15 to 25 watt soldering iron or an iron
with a temperature controlled tip (approximately 700 degrees) .
The tip should be no wider than the solder pads on the printed
circuit board. Use only a fine gauge rosin core solder (60/40 or
63/37). Do NOT use acid core solder as this can severely damage
a printed circuit board. When soldering, keep the soldering iron
tip on the pad just long enough for the solder to completely
flow. If the solder does not draw up the wire then more solder
is required. Do not use so much solder that it overflows the
pad. If a solidified joint is not shiny, it may be a cold solder
joint and should be remelted. The soldering iron tip should be
cleaned frequently by wiping on a damp sponge
When you have completed assembly of a board, inspect it for
unintended solder connections or "bridges", as well as unsoldered
leads. After soldering, it is recommended that the rosin flux be
removed from the board using flux remover, FREON or paint-thinner
tyne solvent. This will make looking for soldering problems
easier and give the board a clean, professional appearance.
IC SOCKET INSTALLATION
Integrated circuit (IC) sockets can be installed by first
inserting them into the printed circuit board, then placing
another flat board over the IC sockets and finally turning over
this sandwich. Be sure that each Ie socket is inserted into the
proper location and is oriented such that pin I of the socket
corresponds to the pin I indication on the PC board layout
legend. (Refer to figure IA to identify pin I on an IC sockeL)
To solder IC sockets, first solder just two opposite cqrner pins
North Star HORIZON Computer
14

for all sockets being installed. Then remelt the corner
connections while applying pressure down on the board. This will
remove any gaps that may be present between the IC sockets and
the PC board. Finally, solder the remaining pins of the IC
sockets.
DIP HEADER SOLDERING
Wren making jumper connections on a DIP header, solder resistor
or capacitor lead snippings between the leads to be connected.
Wren more than two pins are to be connected together, bend a
single wire so that it routes to each pin, and solder each pin
or.ce. Insert the header in an IC socket on a PC board to hold it
dlring soldering. Overheating the pins with the soldering iron
will melt the plastic of the header. If there are multiple
jlmpers on a header, make sure that no unintended connections are
made by carefully routing the jumpers, or by insulating each
jllmper with some wire insulation.
RE:SISTOR AND CAPACITOR INSTALLATION
Te, install resistors or capacitors, first make right angle bends
iI' the leads to fit the PC board hole spacing. (Some capacitor
lE,ads are already appropriately spaced and do not need bending.)
Tl,en insert the leads as far as possible through the correct
hc,les in the PC board and spread the leads slightly on the solder
so_de of the board to keep the part in place. After a group of
resistors or capacitors has been inserted, then solder the leads
OIl the solder side of the board and snip off the excess leads as
c_ose to the board as possible. Use caution to avoid eye injury
flam flying bits of wire. Save the lead clippings for later use
ill making jumper connections.
PI{INTED CIRCUIT BOARD LAYOUT
T'1e white component layout legend is printed on the component
side of a printed circuit (PC) board. All components are
i1sprled from this side (component side) and soldered on the
a ther side (solder side). Locations on the PC board are
identified by two--character codes as marked on the board: a digit
f'lilowed by a letter indicating the horizontal and vertical
cJordinates of the location. Note that in North Star kits, IC's
C3n be found on styrene pads in positions corresponding to their
intended locations on the PC board.
Pin numbering conventions for the S-100 edge pins are as follows:
When Viewing the component side of the board (with the pin edge
facing down), pins 1,2, ..• ,50 range from left to right. When
viewing the solder side of the board, pins 100, 99, ... , 51 range
from left to right.
15
North Star HORIZON Computer

MOS INTEGRATED CIRCUIT HANDLING
Some North Star PC boards use some MOS-type IC's. These parts
are identified as such in the instructions, MOS devices can be
damaged by static electricity discharge. so special handling is
necessary to protect them. Handle MOS devices as little as
possible and avoid touching the pins. Place the conductive foam
or tube which contains the MOS device onto the PC board before
removing the device from the foam or tube. Also, be sure both
hands are touching the foam or tube when the device is removed
from the foam or tube.
Once a MOS device has been installed in aPC board, handle the
board as little as possible. Of course, never insert or remove
any IC while power is applied to the board, and never remove or
insert aPC board while power is applied to the motherboard.
North Star HORIZON Computer
16

<=======~Cl: '00 MFO )F=======>
pmitive (+) lead ~ .
Axial Lead
Electrolytic Capacitor Resistor
Network
c=======eDD::=)~====
Resistor
Regulator (To-nO)
Transi~;tor and
Regulate" (To-92)
positive
(+1 lead
+
+
+
~
1 ~ I
Quick-Cc,nneet
LU~I
Ceramic
Disc
Capacitor
Dipped
Myla,
Capacitor
Dipped
Mica
Capacitor
Dipped
Tantalum
Capacitor
In1:egrated
Circuit (Ie) I C Socket
DIP Header
17
Figure 1A. Identification and orientation of components.

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18
COver !VI
Ovntin h
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COver
mOUntin
at b9hole ....
ott0t7l
lOp
Identificat"
Ion and .
Onentat"
IOn of Sh
eet Meta{ Parts
000000000000
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"-------------'C>

POWER SUPPLY ASSEMBLY
Assl,mbly of the power supply is the first step in the assembly of
the HORIZON. In the following instructions, use of the words
"leCt" and "right" refers to those directions when facing the
frollt of the computer.
Pl. Check to be sure you have all the parts for the power supply
by referring to the parts list. Identify each of the wires
listed in Table 1 (at the end of this section) and neatly
tag each wire with the appropriately numbered wire label
from the wire label card. The label should be placed near
end A to aid in orienting the wires.
P2~ Mount the fan and fan guard to the back panel so that the
following order results from outside to inside: 6-32x7/8"
machine screw heads, fan guard, back panel, fan, 16 lock
washers and 16 nuts. The outside of the back panel will be
the side away from you when the large fan opening and two
rectangular switch holes are on your upper right. See
figure IP. Orient the fan so the power connections are on
the lower right and the airflow arrow points outward.
P3. Mount the fuseholder to the outside of the back
position and orientation as shown in figure IP.
side lug away from the fan, and fasten with the
fuseholder nut. Insert the 5 amp fuse into the
and twist on the fuseholder cap.
panel in the
Orient the
large
fuseholder
P4. Install the line filter to the outside of the back panel In
the position and orientation shown in figure IP. The
following order should result from outside to inside:
6-32xl/2" machine screw heads, line filter, back panel, lock
washers, and nuts.
P5. Snap the reset paddle switch into the top rectangular hole
to the right of the fan from the outside of the back panel.
Orient the switch so that the paddle points toward the fan.
P6. Snap the power rocker switch into the rectangular hole just
below the reset switch from the outside of the back panel.
Orient the switch so that lugs 13 and 16 are to the left.
19 North Star HORIZON Computer

P7. Slip end B of wire #2 (see wire descriptions in Table 1 at
the end of this section) onto the top center lug (#2) of the
power sw itch.
P8. Slip end B of Wlre #3 onto the center lug of the fuseholder.
p9. Slip end A of wire #4 onto the side lug of the fuseholder.
PIIL Slip end B of Wlre #4 onto the bottom center lug (#5) of the
power switch.
Pll. Slip the B ends of wires #7 and #8 onto the two fan lugs.
The fan lugs may have to be bent slightly in order to slip
on the wires. Twist the wires together and leave the A ends
unattached for now. Check your assembly to this point with
figure lP for correctness. Set the back panel aside for
now.
P12. Mount the four adhesive-backed rubber feet onto the bottom
of the chassis frame, approximately 1" in towards the center
from each corner.
P13. Orient the chassis frame on the rubber feet so that the four
1/4" oval holes are on the right, away from you. The front
of the chassis is now closest to you.
P14. Mount the 180,000uf electrolytic capacitor as follows:
First attach a 6-32xl/2" tightening machine screw to the 3"
diameter capacitor clamp with a lock washer and nut. Next,
mount the clamp to the chassis frame in the location and
orientation as shown in figure 2P, using three 6-32x3/8"
machine screws and lock washers. Do not tighten the machine
screws yet. Next, insert the caoacitor into the clamp,
oriented as shown in figure 2P, forcing the bottom of the
capacitor to be flush with the frame. Finally, tighten the
clamp tightening machine screw and the three clamp mounting
machine screws.
PlS. Mount the stud diode mounting bracket in the location and
orientation shown in figure 2P, using two 6-32x3/8" machine
screws and lock washers.
P16. Mount end A of wire #13 and the stud diode with the longer
blue wire (#9) to the right hole of the stud diode mounting
bracket. The following order should result from back to
front: stud diode, mica washer, teflon ring, mounting
bracket, mica washer, #10 flat washer, end A of wire #13,
lock washer, and nut. Be sure the teflon ring is inside tne
bracket hole to insulate the diode from the bracket. Leave
end B of wire #13 and end A of wire #9 unattached for now.
P17. Similarly mount end A of wire #14 and the other stud diode
(wi th wire #10) to the left hole of the stud diode mounting
North Star HORIZON Computer
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