Radio Shack TRS-80, TRS-80 Model I, 26-1001, 26-1201, 26-1140 Technical Service Data

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MODEL I LEVEL
KEYBOARD,
1\
BOARD
EXPANSION INTERFACE
SAFETY PRECAUTIONS
Block
Diagram Disassembly General GridTrace
IC Line Logic Miscellaneous Parts
Operating
Location
CPU Board
Pinouts
Definitions
Charts.
List
The llliing of ony
constituteInany
HowardW.Sam, replacement
from manufacturers
& Terminal
information
See
Folder
See page 19
Instructions
Instructions
Guide
Guides
. .
..
Adjustments
IS,.
available
co,.
& Co. Inc
port. The
fU"~lIhed
of
the
particular
CSCS3-A
Howard
4300
replocement
a
recommendation.
.•asto
numbers
of
to
HowardW$oms
type
West
warrantyorguoranty
'hoe
qualIty
'hes.
parts
01
replacement
Page
6,27
..24,25,26
15,16,17,18
W.
Sams
62nd
Street,
port
herein
and
SUltoblhty
have
been compiled
& Co.. Inc
port
MONITOR
See
Folder
CSCS3-B
PRELIMINARY SERVICE CHECKS
ENCLOSED
INDEX
29
13
19
20
dolu
listed
4 4
of such
by
& Co
P.O.
not
by
the
Photos
Cassette CPU Board 10,11,12,21,22,23 Level
Partial Keyboard 14 Safety Schematics
CPU 2,3,30,31,32,33
Power Schematic Troubleshooting
..
Box 7092,
Reproductionoruse
contentinany
respect
e 1985
"300 West 62nd Str
Pdn'ed
Modification
II
ROM Board
Precautions
Supply
Notes
Inc.
Indianapolis,
monner.
to
the
VI.
of the
How""
W.
sam,
..t,P.O.
in U.S. of
Amefico.
without
is
information
& Co., Inc.
Counter
expre
prohibited.
lox
7092. Indianapolis. Indiana
Indiana
..
permission,
No
contained
poten'
Board 20
85CC14942 DATE 2.85
Page
7,8,9
46206
U.S.A.
of
editorial
Iiobilityi,os.Jumed
herein.
0(
<16206
14
19
5,28
piC1oriol
U.S.A.
9
with
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PRELIMINARY SERVICE CHECKS
RADIO SHACK
....O..D..
E_L_I_L..EV_E_L..I..I_
TRS·SO
This data provides the user designed for malfunctions.
Check all correct
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ROM
SELECT SHUNT
Rom Select Shunt
M Level I
.
CJ)
()
CJ)
or
LevelIIBasic ROMs are installed. Use the follow-
ing charttodetermine which pins are shunted.
Z3 PINS BASIC BASIC
(Z3)
CPU
(Z3)
is set up in accordancetowhether
LEVELl
()
1-16 2-15 3-14 4-13
5-12 6-11 7-10 8-9
Open Shunted Shunted Open Shunted 2-15 Shunted Shunted 3-14 Open Shunted 4-13 Shunted Shunted Shunted Open Shunted 7-10
with
quick
isolation
interconnecting
hookup
before making service checks.
Disconnect all external peripherals from systemtoeliminate possible external
a time-saving service
and repair of
cables
for
good
computer
connections
the
malfunctions.
ReplacementorrepairofPower Supplies, Board, Expansion Interface Board and connectors
may be necessary
after
Monitor
the
malfunction
been isolated.
MISCELLANEOUS ADJUSTMENTS
AND KEYBOARD
LEVEL
II
Shunted
Shunted 5-12
RAM SELECT SHUNT
RAM Select Shunt
amount of RAM memory (4K or 16K) installed on
the
Use
following
shunted.
271
PINS
1-16
6-11
8-9 Open
tool
system
and
computer
CPU
(Main)
Boards or
has
(Z71)
CPU
AND KEYBOARD
(Z71)
is set up in accordancetothe
charttodetermine which pins are
4K 16K RAM
RAM
Open Shunted Shunted Open
Open
Shunted Shunted Open Open Shunted Shunted Open Open Open
Open
CPU
Board .
5V
12V AND
NOTE: Perform
Connect the (Z2).
Adjust
Connect the (Z1).
Adjust
12V AND
ADJUSTMENT
12V
inputofaDCvoltmetertopin 3 of Regulator IC the 12.0V
input the5VAdjust
5V
ADJUSTMENT EXPANSION INTERFACE
NOTE: Perform 12V
Connect (Z20).
Connect (Z21).
the
inputofaDCvoltmetertopin 3ofRegulator IC
Adjust
the
the
inputofaDCvoltmetertopin 3ofRegulator IC
Adjust
the5VAdjust
s
Th.
lI,ting of
constituteinany
Howard W. r.ploc.ment from information furnished to HowardW.$oms & Co ..
manufacturersofthe
CPU
AND KEYBOARD
adjustment
Adjust
before5Vadjustment.
Control (Rl0)
for
11.9V.
of aDCvoltmetertopin 3 of Regulator IC
adjustment
12V
Adjust
I~
lelrTII
any
ovailable
cos.
Saml
& Co
port. The
Control
0 rec:ommeondotion.
.•
Inc
numbers
particular
(R5)
for
5.0V.
before5Vadjustment.
Control
Control
..
(R7)
(R8)
Howard
4300
West
r.plocement
as
to
the
quality
of
the,.
type
of
replocement
for
for 5.0V.
W.
62nd Street, P.O. Box 7092,
port tMreln
warrantyorguaranty
and
pam
hove
11.9V.
Sams & Co., Inc.
does
not
port
Inc
listed.
of such
.. by the
by
suitability
been compiled
HORIZONTAL AND VERTICAL CENTERING KEYBOARD
Type and run the
(O,X): (X,O):
Monitor
SET (127,X) SET (X,47)
tangle on the
10
CLS: FOR X =0 TO
20
IF X>47 THEN
30
SET
40 SET
following
40
Basic programtoproduce a rec-
screen:
127
50 NEXT X 60 GOTO 60
Adjust
the Horizontal Center Control (R20) and Vertical
Center Control
(R21)tocenter the rectangle on the
screen.
Indianapolis,
R_oductlon
conl..,t,
r.sp«'
~
4300 W.., 62nd
PrintedInU.S.of"memo.
11185
0.-
.....
In
to Howanl
without
ony
manner.
the u
..
of the Infarmotlon contolned
W.
Sam.
St,..t. P.O.
i.
Indiana
_p'."
prohibited. No pot..... liobUlty
& Co.,
Inc:.
lax
7092. Indianapolis. Indiana
46206 U.S.A.
pennl..lon.01edltoriol
"-<eln.
85CC14942
I.
auumed
~
DATE
0.-
CPU
picto.-lol
with
U.S.A.
2-85
AND
Monitor
CD
PRELIMINARY SERVICE CHECKS (Continued)
SERVICE CHECKS
SEE INTERCONNECTING DIAGRAM AND PHOTOS CIRCLES WITH THOSE FORMED.
POWER SUPPLY
(A)
Disconnect the from tween pin 1 and pin 3 and 23.6V between pin 2 and pin 4 voltages are missing, replace the Power Supply Module.
(B)
Check measurement is ment
(CPU
BOARD)
Connector
for
of
CPU
J1A and check
of
the Power Supply Plug (P1A). If
5.0V at pin 3ofRegulator IC not
the5VAdjust
IN
THE FOLLOWING DATA FOR SERVICE CHECKS TO
Power Supply Module(PT1)
correct, check the adjust-
Control
for
18.5VAC be-
(R5).
the
(Z1).Ifthe
CD
® MONITOR DEAD
® CASSETTE PORT INOPERATIVE
TO
MATCH THE NUMBERINTHE
BE
VIDEO DISPLAY UNSTABLE
(A)
Check the Coil (L4) and Vertical Hold Control (R13B) located on the rear of the Monitor.
(A)
Check Fuses Monitor.
adjustmentofthe Horizontal Hold
F101
and F103 located inside the
PER-
(C) Check
COMPUTER DOES NOT COME
(A)
(B)
(C) Check RAM ICs Z13 thru Z20 by
KEYBOARD
(A)
(B)
(C)
for
11.9V at pin 3 of Regulator IC
the
measurement is
justmentofthe 12V
Seeifthe Select see "ROM Select Shunt Z3" laneous Adjustments.
Check Regulator IC (Z40)bysubstitution.
If only one key is
contacts
key key is contacts tacts
If several keys are not working, check the ribbon cable between Keyboard and possible
If
wrong character appears on the screen when a key is pressed. Check Character Generator IC
ROM
Shunts
with
still
defective, check
and solder
with
an ohm meter.
open
not
correct, check the ad-
Adjust
Control (R10).
UP
PROPERLY
Select
Shunts
(Z71)
have been set up properly,
(Z1)
not
working properly, clean the
a spray
joints.
circuits.
(Z29)bysubstitution.
sectionofMiscel-
and
Microprocessor
contact
for
breaks at
Check the key con-
(Z3)
substitution.
cleaner. If the
CPU
(Z2).
and RAM
the
key
board
Monitor
IC
for
If
(A)
Check the Cassette cables for looseorbroken wires and also check Board and sion Interface Board
(B)
If the Cassette the Computer Off. Use for
an open
of
RelayK1to Relay contacts are shorted.
POWER SUPPLY (EXPANSION INTERFACE)
(A)
Disconnect the Expansion Interface Power Sup­Iy Module (PT1) from
19.7VAC between pin 1 and pin 3 and 23.6V between pin 2 and pin 4ofthe Power Supply Plug Power Supply Module.
(B)
Check the measurement is incorrect, check the adjust­ment
(C) Check
the measurement is incorrect, check the adjust­mentofthe5VAdjust
DISK DRIVE PORT INOPERATIVE (EXPANSION INTERFACE)
Connectors
motor
circuit
the center pin at the
K1.
If the pins are shorted,
are
sticking
(P9).
If the voltages are
for
11.9V at pin 3ofRegulator IC
of
the 12V
for
5.0V at pin 3ofRegulator IC
Connector
J6, J7 and J8 on Expan-
for
good connections.
will not
an
ohm
from the center pin at one end
or Diodes CR9 and CR10
Connector
missing,
Adjust
Control
Control
J3 on
stop
running, turn
metertocheck
other
either
Relay
J9 and check
replace the
(R7).
(R8).
end
(Z20).
(Z21).
CPU
of
K1
for
DC
If
If
@ NO VIDEO ON MONITOR
(A)
Check the video cable
Connector
Video
(B)
Check the (R102) and Brightness Control (R103) located on the
Monitor.
VIDEO DISPLAY NOT CENTERED
(A)
Check the
the
(R20)
CPU
Control on Centering" justments.
II
(J2)
adjustmentofthe
adjustmentofthe Horizontal Center
and Vertical Center Control
Board,
section
for
broken wires and the
for
good
connection.
Contrast
ON
MONITOR
see"
Horizontal and Vertical
of
Miscellaneous
Control
(R21)
Ad-
(A)
Check Disk Drive cables
wires and Clean Connector J5 cleaner.
(B)
Check Disk
LINE PRINTER PORT INOPERATIVE (EXPANSION INTERFACE)
(A)
Check the Line Printer cable for loose or broken
wires and Connector J4
Clean
cleaner.
ConnectorJ5for
ControllerIC(Z42)bysubstitution.
ConnectorJ4contacts
for
loose or broken
good
contacts
for
good connections.
connections.
withacontact
withacontact
MONITOR
PRELIMINARY SERVICE CHECKS (Continued)
@
HORI1
@
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VERT
HCl.D
CHASSIS
F103
0
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SIZE
VERT
rnD
Q
_
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F~'
0
PRELIMINARY SERVICE CHECKS (Continued)
CASSETTE
L
Y
@)
CASSETTE
2 I
34
JS
DISK
.J
DISK
CCWTROlLER
Q 2
142
\!.J
2
MIVE
PORT
Q 34
~
8 L
t:.:
PRINTER
PORT
I20VAC
8
....
~-~
'V'----.,
MONITOR
P I CPU
POWER
SlI'flt
y
@
MAIN
BOARD
0-----
r-----~
LEVEL
IT
ROM
CASSETTE
HOOIF
lCATlOH
COUOfTER
!IOARD
BOARD
@
HOR~
CENTER
R21
{
VERT
CENTER
MON
ITORVIDEO
BOARD
19.7VAC
CPU
EXPANSION
J1
INTERFACE
40
BOARD
8 RIO
@
Rf6lLAT~
5.~
@)
EJ
CJ@
Rf6tl.AT~
m
/6
11.9V
BBBBBBBB
"Y"
BOARD
FWl
®
lCa
2
HI~
@)
Z40
SU'"FERED
INTERFACE
39
40
'--------I
J3
IllS
PORT
40
52
RESET
INTERCONNECTING DIAGRAM
X
Z33
FWl
SHMTS
KEYBOARD
INTERCONNECTING DIAGRAM
III
PRELIMINARY SERVICE CHECKS (Continued)
GENERAL OPERATING INSTRUCTIONS
POWERUP(COMPUTER ONLY)
words
Turn On the Computer. The
pear on the word" Monitor
POWER
1.
Turn On the Expansion ·Interface.
2.
TurnOnthe Disk Drives (Terminal Drive 26·1164A, first) and then any
3.
Put a into will of screen along prompt
NOTE: Disk Drive, puter. A screen. Press Enter key and the pear followed by a now in Basic mode.
RESET
Press the Break key and the Reset the Computer) to reset the Drives are attached, mation This
DISK OPERATING SYSTEM (DOS)
Type DIR and press the Enter key programs and the contains
list
To load a program from a gram and press the Enter key. Use a of the Disk Drive
If no
NOTE: Computerisin the Disk Basic mode.
To get back to the DOS from Disk Basic mode, type
Monitor
READY" and a
screen. The
UP
SEQUENCE (WHEN USING DISK DRIVE)
diskette
Disk DriveO.Turn On theComputer. The
automatically
the
Disk
character.
If
into
will
reboot
that
numberofthe Disk Drive
the
programsondiskette
number
Basic
screen. Press the Enter key once. The
prompt
Computerisnow
other
peripherals.
(containing
boot
up from Disk DriveO.The version
Operating System
with
the words "DOS READY" and a
an Expansion
hold
double"
Disk Drive 0 and press
the
are on the
information
which
is given, the
program
Interface
down
Break key when
MEM SIZE?"
prompt
ComputertoBasic mode.IfDisk
insertadiskette
Computer
diskette
desired. Example: Type DIR:2to
in Disk Drive
diskette,
contains
system
will
not load from
nMEM SIZE?"
character
DOS, Disk
character. The
from Disk Drive
will
in Basic mode.
Operating
will
appear on the
unit
is used
turning
will
appear on
word"
READY"
button
(on
containing
only
the Reset
to
displayadirectory
in Disk DriveO.Type DIR :
holding
the
2.
type the name of the pro-
colon
and the
the programtobe loaded_
will
assume
diskette
will
appear on the
System)
Computer
Monitor
without
On Com·
Monitor
will
Computer
right
rear
DOS infor-
button.
O.
diskette
which
number
Disk Drive
unless
CMD"S"
willbelost
ap·
DISK BASIC
To load Disk Basic sert a DOS key and DOS, type in memory
To load a program from a gram name enclosed in
load from a Disk Drive the
ample: LOAD
To save a program SAVE and the program name in
key. To save a program
a
than Disk Drive0,add a the end Disk Drive
ap·
is
FORMATIINGADISKETIE
NOTE: This procedure System diskette
of
containing2or to
A blank saving data. To diskette
DOS
the Enter key.
of
blank
tions
CASSETIE
To load a program from tape, type CLOAD (with
the program name enclosed in quotes), play when program has been loaded.
and press the Enter key. Any program in
when leaving Basic
diskette
diskette)
follow
CMD"S"
will
Disk
Drive
of
the program name. Example: SAVE
1.
sections
thus
format a
diskette
diskette
with
diskette)
diskette
on the
Monitor
OPERATION
mode
and press the Enter key. Prompt
O.
To save a program
the
the program name enclosed in quotes), record mode and press the Enter key. A dicate
when
writing
modebyusing
into
the Computer,
containing
into
Disk Drive0,type BASIC, press the Enter
prompts.
be lost.
number
"SAMS:1"
required for normal
formatted
more Disk Drives.
mustbeformatted formatadiskette,
the
format
into
After into
Disk Basic (usually a partofthe
Togofrom Disk Basic
and press the Enter key. Any program
diskette,
quotes
other
than Drive0,add a
at the endofthe program name. Ex-
for Disk Drive
ontoadiskette
ontoadiskette
colon
and the Disk Drive
does
must
containing
program on it (usually partofthe
the Disk Drive, type FORMAT and press
the program has been loaded, insert a
the Disk Drive and
screen.
onto
tape, save CSAVE (withorwithout
has been completed.
boot
type LOAD and the pro-
and press the Enter key. To
in a Disk Drive, type
quotes
in a Disk Drive
not
copy Disk Operating
disk
be used
Use"
DOS
information.
before it can be used
bootupon DOS, insert a
"CMD"S".
up on DOS. In-
1.
and press the
"SAMS:1"
operations. A
only
with
Back-up"
follow
put
the Recorder in
will
put
the Recorder in
prompt
memory
mode
to
colon
and
Enter other
number
the instruc-
or
for
systems function
for
without
indicate
will
at
in-
IV
PRELIMINARY SERVICE CHECKS (Continued)
PRELIMINARY SERVICE CHECKS (Continued)
@
CE
HORll
R20
{
CR10
TER
CR9
K1
®
CASSErE
J3
Af1A\
@
V
DEO
J2
f3C\
~
~
POWtRSWTCH
Z29
J1
POWER
Sl
@
®
r
..
@
®
@
SELECT
ROM
SHU
Z3
TS
@
RAM
SELECT
Z71
SHU
TS
Z40
KEYBOARD
@
®
CABLE
CPU BOARD
VIII
CPU BOARD
V
PRELIMINARY SERVICE CHECKS (Continued)
@
..
PRELIMINARY SERVICE CHECKS (Continued)
G~0
OS
DREpaR
J5
LINE PRI
TER
12V
ADJ
R7--
@ 120V
{
PI
Z20
5V
AoJ
~~_j~RT
3
BUFFERED
INTERFACE BUS PORT
~~-J3
@
:tl
3:>
52
0
0
0
m(f)
r-z
->
r-(')
m~
<0004
~:tl
_(f)
-eo
o
@{
PI
R8
~
OV
3
Z21-....JIi==
POWER
J9
EXPANSION INTERFACE BOARD VI
EXPANSION INTERFACE BOARD
VII
PRELIMINARY SERVICE CHECKS (Continued)
PRELIMINARY SERVICE CHECKS (Continued)
@
CE
HORll
R20
{
CR10
TER
CR9
K1
®
CASSErE
J3
Af1A\
@
V
DEO
J2
f3C\
~
~
POWtRSWTCH
Z29
J1
POWER
Sl
@
®
r
..
@
®
@
SELECT
ROM
SHU
Z3
TS
@
RAM
SELECT
Z71
SHU
TS
Z40
KEYBOARD
@
®
CABLE
CPU BOARD
VIII
CPU BOARD
V
ENVIRONMENT
PRELIMINARY SERVICE CHECKS (Continued)
PREVENTATIVE MAINTENANCE
Computers though maintain Monitor,
ELECTRICAL POWER
Variations in the line voltage can power non-interruptable
KEYBOARD
liquids power printed tact
DISK DRIVES
Clean the read/write headsofthe Disk Drives about ing kit.
Handle of
alignment.
Store on the back of
PRINTERS
Carefully vacuum the Printer regUlarly. Wipe surface areas clean using a The oil
perform best in a clean, cool area
home
Computers
a smoke-free area around the Computer. Do
Printer,orother
line
not
used by appliancesorother
spilled
into
outlet.
Then,ifcircuitryorcontacts
circuit
cleaner and lint-free wipers on accessible
disksintheir
board
carefullytopreserve proper
If the
disk
will
collect
are not affected by
power
devices.
affect
power
supply
may be neededtocure the problem. Do
the Keyboard can ruin it.
with
distilled
disk
drive
protective
protective
abrasive
water and let it dry. Use a
disk
must
be transported, place an
covers and never
covers.
grit
and
dust.
the Computer. Trytoavoid these
heavy
head alignment. A sudden bumporjolttothe
The
thatisbelow80degrees Fahrenheit and freeofdust cigarette
Immediately
are
smoke as
not
block
current
demand devices. A power-surge protector, power-line
afteraspill
contaminated,
connectors
onceamonthorafter
touch
dust
will
the
disk
act
colton
and
old
as a blanket.
muchascommercial
cabinet ventsofanyofthe
occurs,
disassemble
swabtoclean between the keys. Use a non-abrasive con-
contacts.
diskinslot
surface. Observe the
Computers
fluctuationsbyusinganAC receptacle that is on a
not
switch
powerOnand
disconnect
the Keyboard and
100
hours
usage. Use
Disk
and
close
door
disk
handling precautions
light
all-purpose cleaner. Do
This
can cause
and smoke particles. Even
are affected,itis
Computer
the
Computer
carefully
only
Drives can
during
componentstooverheat and fail.
system; Computer,
Off
frequently.
power plug from
rinse the Keyboard
an approved head clean-
knock
the
transport.
not
oil the machine.
belter
conditioner,
disk
head
usually
found
AC
out
to
or
::z:J
3:>
O~
cO
men
r""::I:
->
r""O
m"
<~
~::z:J
_en
-cio
o
STATIC ELECTRICITY
Static
electricity
and materials, and maintain good
MONITOR
Use an chassis at preserve the glare-reduction feature.
high
isolation
(chassis
brightness
discharge
transformer
connectedtoone sideofthe AC line). The faceofthe
level except when pattern is being changed periodically. Use
can
affect
with
the Computer. In ordertominimize
humidity
any
in the
Monitor
Computer
that
does
environment.
not
come
the
possibility,
as partofthe system
Monitor
should
caution
never be
use
anti-static
since
leftonfor
when cleaning anti-glare screens,
some
mats, sprays,
Monitors
long
periodsoftime
tools
use a HOT
to
IX
MONITOR
PRELIMINARY SERVICE CHECKS (Continued)
@
HORI1
I«llD
@
VERT
HCl.D
CHASSIS
F103
0
]A
SIZE
VERT
rnD
Q
_
®
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PRELIMINARY SERVICE CHECKS (Continued)
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III
PRELIMINARY SERVICE CHECKS (Continued)
TEST EQUIPMENT AND TOOLS
CPU
BOARD
ITEM
CR9 4800026 CR10 4800026 K1 PT1 R5 R10
R20
R21
Z1 Z2 Z3 Z13 3108009
thru
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Z29
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4750018
4750018
3100001
31ססoo1
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3108001
3110001 2100041
TEST EQUIPMENT
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Probe
PARTS LIST
DESCRIPTION
Diode, 1N982A Diode, 1N982A Relay,
Motor
Control, Power Supply Module Control,5VAdjust, 1000 Ohms Control, 12V Adjust, 1000 Ohms Control, Horizontal Center, 100K Ohms Control, Vertical Center,
100K Ohms IC, Regulator, MC1723CP IC, Regulator, MC1723CP Shunt,
ROM
Select IC, RAM, MB8116E IC, RAM,
IC, Character Generator, 8046670 IC, Character Generator, MCM6670 IC, Microprocessor, IC, Microprocessor, Z80 Shunt, RAM Select
5V
D780C·1
TOOLS
Phillips Screwdriver
Small Screwdriver
Contact Cleaner low
Voltage Soldering Iron
Desoldering Equipment
AND
DESCRIPTION
EXPANSION INTERFACE BOARD
ITEM
PT1 R7
R8
Z20
Z21 Z42
PART NO.
4000004 4750019
4750019
31ססoo1
31ססoo1
MONITOR
ITEM
F101 F103 L4 R13B
R102
R103
PART NO.
426973 99328
141017 141022
140980 140711
DESCRIPTION Power Supply Module
Control, 1000 Ohms Control,5VAdjust, 1000 Ohms
IC, IC, Regulator, MC1723CP IC, Disk Controller, FD1771
DESCRIPTION Fuse, 1A @250V, Fast
Fuse, 5A @250V, Fast Coil Horizontal Hold Control, Vertical Hold,
200K Ohms Control, Contrast, 500 Ohms Control, Brightness, 200K Ohms
12V
Adjust,
Regulator, MC1723CP
B-{)1
Acting
Acting
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2
0
0
0
men
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10
m"
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Used in 4K versions
DISASSEMBLY INSTRUCTIONS
CABINET REMOVAL
Remove six screws from cabinet bottom. Remove cabinet top and ponents are now accessible for service.
CABINET REMOVAL EXPANSION INTERFACE
Remove six screws from cabinet bottom. Remove cabinet bottom
service.
bottom
from unit. All components are now accessible for
CPU
AND KEYBOARD
from Keyboard and
CPU
Board. All com-
CABINET REMOVAL MONITOR
Remove five screws holding cabinet back and remove back. All components are now accessible for service.
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A PHOTOfACT
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STANDARD
WITH
Ii'·i.i1n.,.,
W.
Sam.
NOTATION
& Co
.•
Inc.
••
1985
SCHEMATIC
SEE LINE DEFINITIONS ON PAGE
19
RADIO SHACK TRS·80
MODEL I LEVEL II
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FOR
TERMINAL
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STANDARD
WITH
li'·iYili'-f.'i.
W.
Sama & Co.•Inc.
NOTATION
SCHEMATIC
1985
SEE LINE DEFINITIONS ON PAGE 19
J
GENERAL OPERATING INSTRUCTIONS
POWERUP(COMPUTER ONLY)
"MEM
Turn On the Computer. The words pear on the word "READY" and a Monitor
POWER
1.
Turn On the Expansion Interface.
2.
Turn On the Disk Drives (Terminal Drive 26·1164A, first) and then any
3.
Put a into will of screen along prompt
NOTE: If an Expansion Interface Disk Drive, hold puter. A screen. Press Enter key and the pear now in Basic mode.
RESET
Press the Computer)toreset Drives are attached, insert a mation This
DISK OPERATING SYSTEM (DOS)
Type DIR and press the Enter key
programs and the contains
list
programs on
To load a program from a diskette, type the nameofthe pro-
gram and press the Enter key. Use a of the Disk Drive
no
If
NOTE: Basic program
Computer
To get back to the DOS from Disk Basic mode, type
Monitor
screen. The
UP
SEQUENCE (WHEN USING DISK DRIVE)
diskette
Disk DriveO.Turn On the Computer. The
automatically
the Disk Operating System will appear on the
character.
followed
the
Break key and the Reset
into
will
reboot the
that
numberofthe
the
number is given, the system
is in the Disk Basic mode.
screen. Press the Enter key once. The
prompt
Computerisnow
other
(containing DOS, Disk Operating System)
boot
with
down
double
"MEM
by a
Disk Drive 0 and press
Computer
are on the
Disk Drive
information
diskette
which
will
character
peripherals.
up from Disk DriveO.The version
the words "DOS READY" and a
Break key when
SIZE?"
prompt
character. The
the
ComputertoBasic mode. If Disk
diskette
from Disk Drive
to
diskette
contains
in Disk DriveO.Type
holding
desired. Example: Type DIR:2to
in Disk Drive
the programtobe loaded.
will
not load
from
SIZE?"
will
in Basic mode.
unit
is used
turning
will
appear on
word"
READY" will ap-
button
(on
containing
only
the Reset button.
display a
the
2.
colon
and the number
assume Disk Drive
diskette
will
ap·
appear on the
Computer
Monitor
without
On Com·
Monitor
Computer
right
rear
DOS infor-
O.
directory
diskette
DIR
which
unless the
CMD"S" willbelost
DISK BASIC
To load Disk Basic
sert a DOS diskette) key and DOS, type in memory
To load a program from a diskette, type LOAD and the pro­gram name enclosed in load from a Disk Drive the Disk Drive number at the end ample: LOAD "SAMS:1"
To save a program SAVE and the program name in key. To save a program
a
than Disk Drive 0, add a colon and the Disk Drive number at the end Disk Drive
is
FORMATIING
NOTE: This procedure does System diskette
of
containing
to
A blank
saving data. To format a diskette,
diskette
DOS diskette) the Enter key.
of
blank
:
tions
CASSETIE OPERATION
To load a program from tape, type CLOAD (with or the program name enclosed in quotes), play mode and press the Enter key. Prompt when program has been loaded.
and press the Enter key. Any program in memory
when leaving Basic mode by using
into
diskette
formatadiskette
diskette
on the
containing
into
follow
prompts. To go
CMD"S"
will
be lost.
of
the program name. Example: SAVE "SAMS:1"
1_
A DISKETIE
sections
thus
formatted
2 or more Disk Drives.
diskette
with
the format program onit(usually partofthe
into
After
into
Monitor
the Computer,
Disk Drive0,type BASIC, press the Enter
required
must
Disk Basic (usually a partofthe
and press the Enter key. Any program
quotes
other
than Drive 0, add a
for
Disk Drive
ontoadiskette
ontoadiskette
for
must
containing
be formatted beforeitcan be used
the Disk Drive, type FORMAT and press
the program has been loaded, insert a
the Disk Drive and
screen.
boot
up on DOS. In·
from
Disk Basic mode
and press
of
quotes
not
normal
be used
DOS
the
the program name.
1.
in a Disk Drive, type
and press the
in a Disk Drive
copy
Disk Operating
disk
only
Use"
Back-up"
information.
boot
up on DOS, insert a
follow
put
the Recorder in
O.
onto
To save a program the program name enclosed in quotes), put the Recorder in record mode and press the Enter key. A dicate
when
writing
tape, save CSAVE (withorwithout
prompt
has been completed.
"CMD"S".
to
Enter key. To
colon
and
Ex-
Enter other
for
operations. A
with
systems function
for
the
instruc·
without
will
indicate
will
in-
DISASSEMBLY INSTRUCTIONS
CABINET REMOVAL
six
screws
Remove top
and
ponents are now accessible
bottom
from cabinet
from
Keyboard and
4
for
bottom.
CPU
service.
Remove cabinet
Board. All com·
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INPUT
PARAlLEL
OUTPUT
PARAlLEL
ClEAR
IHPUTS
DATA
INPUTS
OUTPUT
I
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He
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He
NC
INPUT
lI2.
IG
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SELECT
7
SN74LS93N
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ICO
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INPUT
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265
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f-
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A9
A8
A7
A636
AS
A4
A3
A2 AI
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mil
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RESET
WAIT
WR
Rli
26
23 22
40
39
38
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34
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AU
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7
04
8
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VIEW
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14 13 12
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RESET
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7
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16
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14
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INVERTING INPUT
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6
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NC
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TOP
VIEW
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11
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II
5
10
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m,
225.
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TOP
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5
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TOP
VIEW
11 II
10
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I
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}
5
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ZS,
26,
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TOP
VIEW
13
l' 11
II
10
2 3 4 5 6 1 8
RIA
fRONT
VIEW
liB,
TOP
Z2I
VIEW
27
POWER SUPPLY
TROUBLESHOOTING
CPU
CLOCK AND DIVIDER
Computer is dead. Disconnect the PowerSupply the
CPU of nector connections at Connector J1A and check for open power cord. If the correct voltages are present, reconnect the Power Supplytothe puter. Check for 5.0V at pin 3ofRegulatorIC(Z1), pin 3ofRegulatorIC(Z2) Diode CR2. If all the voltages are missing, check the Power Switch
If 5.0V is missing, check the voltages and components associated
Regulator Drive Transistor (03), Error Amp Transistor (05)
and pins 2 thru7,10,11and13ofICZ1.
rect, check the adjustmentofthe5VAdjust refer to
If the 11.9V is missing, check the voltages and components associated thru7,10,11and 13 of IC the
If the - 5.0V is missing, check Resistor CR2
MICROPROCESSOR (CPU) OPERATION
Check the 1.774MHz
processorIC(Z40). quency, refer to the "CPU Clock and Divider" sectionofthis Troubleshooting guide.
If the waveform is normal, check the operationofthe reset
signal at pin26of
be Low for approximately.1second when the Computer is
turnedOnand then change toand remain High. If the
reading is incorrect, check Capacitor C42, Resistor
check ICs
If the logic reading at pin25ofICZ40
(pins 7 thru10and12thru15ofICZ40) and address lines
(pins 1 thru 5 and30thru40of
When disabled the
and the address lines are Open (No
readings at the
fers, Tri-State Buffer ICs
read Open (No
Z40 is Low, check Resistor
short to ground. The data and address lines fromICZ40 can
be checked by grounding pin25of IC Z40 and checking the
logic
lights
IfICZ40
turnedOnand suddenly stops, pulses appear on data lines
then suddenly stop, check
thru Z20) by
Board. Check
Connector J1A and 23.6V between pin 4 and pin 2ofCon-
J1A. If the voltages are missing, check the cable and
(S1).
with
"Miscellaneous
with
adjustmentofthe
and check for possible short to ground.
Z52
and Z53 by
lights
readings for High on the data lines and
On) on the address lines.
appears to start operating when the computer is
substitution.
for
18.5VAC between pin 1 and pin 3
CPU
Board and turnOnthe Com-
and - 5.0V at the anodeofZener
Regulator
Adjustments".
Regulator
12V
clock
If the waveform is missingoroff
IC Z40. The
logic
inputs
and
On). If the logic reading at pin25of
Output
If the 5.0V is incor-
Output
Transistor (06) and pins 2
Z2.
If the 11.9V is incorrect, check
Adjust
Control
(R19),
waveform at pin 6 of Micro-
logic
reading at pin26should
substitution.
is Low, the data lines
IC Z40)
readings for the data lines are High
outputsofthe address line buf-
(Z22,
R58
ROM
lights
Z38,
Z39 and
and check for a possible
AlBIC(Z1B)RAM ICs
(PT1)
Transistor
Control
(R10).
Zener Diode
will
be disabled.
On). The
Z55),
for
Open (No
from
AC
11.9V at
(04),
(R5),
fre-
logic
R47
and
logic
will also
(Z13
Verify that the for
a frequencyof10.6445MHz at pin 6ofIC clockisoff Capacitor C43. If the clock is not operating, check Crystal Y1,
Capacitor C43, Resistors by
substitution.
The 10.6445MHz (Z56)tosupply to
pin 6ofMicroprocessorIC(Z40).
of
1.774MHz at pin 8ofIC
or
the signal is missing, check the logic reading at pin 6 IC Z56 fora Low.Ifthe Resistor reading at pin 6 is Low, checkICZ56bysubstitution. for pulses at pin 6ofIC Z40. If pulses are missing, check Resistor tion.
VIDEO
No video on the
emitterofthe Video
is normal, check the Video Connector (J2) forgood connec­tion
and check the video cable.
If the waveform is missing at the
check for a video signal at pin 5ofDriverIC(Z41).Ifthe
signal is present at pin 5 ofICZ41, components associated with Transistor 01.Ifsignal is missing at pin5ofIC Z41, check for a video signal at pin 6 IC Z41. If the signal is present, check IC tion. If the signal is missing from pin 6ofIC waveform at pin 3 of IC Z30.
If the waveform is present at pin 3ofIC reading at pin 2ofIC tion. If the Shift
Reg form is 15ofShift pins4,5,10,11 and12ofICZ10. If the waveform and pulses are present, checkICZ10 by
Video display does not operate in the 32 character mode. Type and run the following Basic program and check for pulses at pins 9 and14of
10 OUT 255,8: OUT 255,0: GOTO
IC
If pulses are missing at pin 9ofIC pins 9 and 10ofIC Z25. If pulses are missing from pin 9
IC
Z25, check Tri-State
by
substitution.
check ICs Z36, Z52 and
present at pin 9 and10ofICZ25, check ICZ25 by tion.
If pulses are present at pin 9ofIC of
IC Z59, checkICZ59 by sent at pin14of IC Z59, check Mux (Multiplexer)IC(Z43) substitution.
CPU
Clock is operating properly by checking
frequency, check 10.6445MHz Crystal
R46
and
R52
clock
is divided by six by the Divide By 61C
the 1.774MHz clock, pin 8 ofICZ56, and fed
Z56.
R67
and checkICZ42bysubstitution.
R64
and check Tri-State
logic
(Register)IC(Z11)
missing
Reg
logic
Monitor
reading at pin 2of IC
at pin 3ofIC
(Register)IC(Z10)
screen. Check the waveform at the
Output
Transistor (01). If the waveform
Z30 is Low, check IC
Flip/FlopIC(Z59).
Buffer
If pulses are
Z54bysubstitution.
substitution.
Check for a frequency
If the frequency is
reading at pin 6 is High, check
BufferIC(Z72)
emitter
check the voltages and
Z30
by substitution. If the wave-
Z30,
check the waveform at pin
and check
substitution.
10
Z59,
check
IC (Z22) and ICs Z23 and Z52
missing
from pin10of
Z59 and missing at pin
and check IC Z42
of Transistor
Z30
is High, check the
If pulses are pre-
Z42. If the
(Y1)
and
incorrect
If the
logic
Check
by substitu-
01,
Z41
by substitu-
Z41, check the
and the
Z30bysubstitu·
logic
for
pulses at
for
pulses at
IC Z25,
If pulses are
substitu-
of
("')
en
("')
en
w
3::J>
0
cO
men
r-::I:
-:J>
of
r-(')
m",
<-t
~:II
_en
-0,
of
14
by
:II
2
o
7
TROUBLESHOOTING (Continued)
VIDEO RAM
following
The
ICs (Z45 thru Z48 and
bit
each defective
puter,
changing the word PRINT in lines 130 and 150
LPRINT.
VIDEO RAM TEST PROGRAM
5 DATA
10
Y =6:X= 15360: POKE
20
IF (PEEK
30
POKE X,160
40
IF (PEEK
50
FOR X= 15360 TO 16383
60
FOR
70
READZ:POKE X,Z
80 IF (PEEK 90 POKE
100
IF (PEEK 110 NEXT Y 120 RESTORE: NEXT X 130 PRINT "MEMORY GOOD" : END 140
IF Y= 6THEN 150
PRINT
"CHECKS BAD" 160
IF Y= 6 THEN 50 ELSE 110
Basic program can be usedtocheck
Z61
thru Z63). The program checks
of RAM and displays on the
bit
found. If a Printer is connectedtothe Com-
the
bad
bit
message can be senttothe
1,2,4,8,16,32,128
(X)AN0
(X)
AND
Y=OTO6
(X)
ANDZ)= Z THEN 90 ELSE 140
X,O
(X)
AND
Y = 7
"BIT";Y;"OF
X,64
64)=64THEN30ELSE 150
64)
= 0 THEN50ELSE 150
Z)=O
THEN 110 ELSE 140
MEMORY LOCATION";
Monitor
the RAM
screen any
Printer by
to
the word
X;
KEYBOARD
not
Keyboard is tween Keyboard and bon cable checks good, check If pulses are
If a
groupofkeys are
Z1A and Z2A and Tri-State Inverter ICs (Z3A and Z4A) con-
to
nected cable
for
If
a single key does withanohmmeter. If the key is erratic and operation, clean the
If a wrong character shows up on the
an alpha or numeric key is pressed, check the video RAM,
to
refer guide IC
CASSETIE
Computer On the cassette motor. Type and run the program. The program will produce the waveform shown in
Figure 1 at pin 2 Off (K1) on the Expansion Interface Board.
the
and check Flip/Flop IC
(Z29)bysubstitution.
Motor
functioning.
CPU
missing,
the keys
open
"Video
will
Control Relay (K1) on the
check IC Z36 by
not
not
circuits.
not
contacts
RAM"
not
save programs
of
Flip/Flop IC Z59 and
Check the ribbon cable be·
Board
for
open
circuits.
for
pulses at pin11of
substitution.
functioning,
functioning.
function,
sectionofthis
(Z28)
check the pins of ICs
Also
check the key
with
a spray
Monitor
and Character Generator
onto
tape or
will
CPU
If the rib-
IC Z36.
check the ribbon
contacts
intermittent
contact
Troubleshooting
Board and Relay
screen when
will
following
toggle
cleaner.
not
turn
Basic
On and
in
The
bit
number schematic. IF the program finds a bad bit, check the schematic that RAM IC by
NOTE:NoRAM IC is used comparing
indicates
gram IC
Z30 by
Tri-State RAM IC the RAM IC checks good, check the Tri-State
with
ated VIDEO SYNC
No vertical sync. Check the waveform at pin
(Z32).
IC substitution. waveform at pin 8 of IC Z57. If the waveform is
8,
check
pin C26
and C27 and check IC Z57 by
form is present at pin
No horizontal sync. Check the waveform at pin11of Counter IC
substitution.
by form at pin 8 check the Horizontal Center Control
C21
and present at pin 8 of IC
No vertical or horizontal sync. Check the waveforms at pin
of
IC Z5. If the waveforms are missing, check ICZ5by
8 substitution.
R28
and
that each RAM IC produces is noted on the
for
the RAM IC that produces that
substitution.
for
bits
5 and 7
bit
6 is bad and
substitution.
Buffer
ICs
(Z44
outputs
and check ICZ6by
to the data lines. If a bad
the defective
If
the
waveform is missing, check IC Z32 by
If
the
the
Vertical Center Control
8,
(Z50).
If the waveform is
If the waveform is present, check the wave·
of
IC Z6.Ifthe waveform is
Z6,
If the waveforms are present, check Resistors
R29
and Sync Amp
bit6.Bit 6 is produced by
with
a NOR Gate IC Z30. If
bits
5 and 7 are good, check
and Z60) are usedtoconnect
bitbysubstitution.
waveform is present, check the
check IC Z5 by
substitution.
missing,
(R20),
substitution.Ifthe waveform is
check ICZ5by
Transistor
bit
bit
Buffer
11ofCounter
(R21),
substitution.
missing
Capacitors C20
substitution.
(02).
and check
the
pro-
the
is found and
associ-
missing
Capacitors
If the wave-
check IC Z50
at pin
10
FORX=1TO100
20
OUT 255,3: OUT 255,0
30
NEXT X
40
OUT 255,4: POKE 14308,0
50
at
8,
FORX=1TO100
60
OUT 255,7: OUT 255,4
70
NEXT X
80
POKE 14308,1: GOTO
If
the
Cassette ing sound from RelayK1on the clicking, check Relay Driver IC ween Low and High. If the foralogic pin 3 of IC Z41. If the Z41, check IC correct reading at pin 1 pin 9
check RelayK1contacts
the
connections
K1isnot
(Z41).
reading that toggles between Low and High at
at pin3,check RelayK1and Diode CR3. If the
of
Flip/Flop IC
Figure 1
10
Motor
is not
switching
CPU
at pins 1 and 3ofConnector
clicking,
The
Z41bysubstitution.
ofICZ41
check the
logic
reading should be
logic
logic
reading is incorrect at pin 3ofIC
is incorrect, check
(Z59).
If pulses are present at pin
3.5V 5ms
OV DC Reference
On, listen
Board. If the Relay is
withanohmmeter
logic
reading is correct, check
If the
foraclick·
and
toggling
reading is
for
pulses at
J3. If
bet-
reading at pin 1 of
logic
9,
8
TROUBLESHOOTING (Continued)
check IC Z59 by checkICZ25 by
If the Cassette relay
contacts
CR9 and CRW.
If the Computer will not save programs the waveform shown in Figure 1 at pin 2ofIC waveform is present, check Resistors check pin 5ofConnector J3 for good connection.ifthe waveform is missing at pin 2ofIC pin 9ofIC Z59. If pulses are missing, checkICZ25 by substitution.
IC
Z59 by
If the Computer a2Vpop, J3. Type and run the
10
X= INT(255)
20
PRINT"X= "; X
30
OUT 255,0: GOTO 10
The number X that appears on the
255
when the 1kHz signal is injected at pin 4ofConnector
J3 and
127 rect, check for pulses at pin10ofICZ4. ing, check the voltages and components associated pins 1 thru14ofICZ4.
substitution.
substitution.
Motor
and check
If pulses are present at pin 9ofIC Z59, check
substitution.
will
1kHz sinewave audio signaltopin 4ofConnector
with no signal injected. If the numbersare incor-
not load a program from tape, connect
If pulses are missing at pin
runs all the time, check for
for
possible shorted Zener Diodes
onto
tape, check for
R53,
R54
and
Z59, check for pulses at
following
Basic program.
Monitor
screen should be
If pulses are miss-
sticking
Z59.Ifthe
R55
and
with
SCHEMATIC NOTES
~
Circuitry Circuitry used in some versions
8 See parts
....
Ground
Item numbers in rectangles appear in the alignment/adjust-
Supply voltage maintained as shown at input. Voltages measured Voltages and Waveforms taken
Terminal Resistors are Value in ( ) used in some versions.
not
used in some versions
list
ment instructions.
with
mode (Main noted. Waveforms taken SweeplTime set forDCcoupling on
SwitchtoAC
is measured when necessary. Each waveform is 9 cm width
withDCreference voltage given at the
of
each waveform. Time in
reading at the endofeach waveform.
title
switch
input
identification
'hWorless, 10% unless noted.
9,
If pulses are present at pin 10ofICZ4and the cassette modification check pin9,check Diodes CR200 and CR201, Resistor check ICs Z1C and Z2C by ent at pin 9 ofICZ24, check for pulses at pins 8 and13of Z24
and pins 9 and10ofICZ25. If pulses are missing from pin 9ofIC Z25, check Tri-State processor IC pulses are missing at pin10ofICZ25, and
Z54bysubstitution.
If
pulses are present at pins 9 and10of at pin13of are present at pin13ofICZ24 check IC
If pulses are present at pin 8ofIC pin 6ofIC Z25.Ifpulses are present at pin 6ofIC check Tri-State missing at pin 6ofIC Z25. If pulses are present at pin 4ofIC substitution. ICs Z22, Z23,
If RelayK1on the Expansion Interface Board is ating, refertothe
shooting
digital
meter. with
screen displayed) unless otherwise
with
in Calibrate position, scope
"0"
to view waveforms
reference voltage waveforms.
JLsec.
may
not
be found on unit.
CounterIC(Z1C)
for
pulses at pin 9 of IC Z24. If pulses are missing at
(Z40)
and ICs Z23 and
IC Z24, check IC Z25 by
Z24bysubstitution.
BufferIC(Z44)bysubstitution.
If pulses are missing at pin 4ofIC Z25, check
Z52
and Z40 by
"Cassette"
guide in the Expansion Interface Folder CSCS3-A.
computer
triggered scope and
per cm, given
in Power Up
afterDCreference
bottom
and IC Z2C has been added,
substitution.
and
Z25, check for pulses at pin 4ofIC
substitution.
input
line
with
pop
If pulses are pres-
BufferIC(Z22),
Z52bysubstitution.
check ICs Z36,
IC Z25 and missing
substitution.
missing
section
at pin 8ofIC
Z24,
check for pulses at
Z25, check IC Z25 by
R200
and
IC
Micro-
Z52
If pulses
Z24,
not
Z25,
oper-
If pulses are
of the Trouble-
If
(")
en
(")
en
(,,)
::D
~~
oS!
cO
mC/)
'-z
-~
'-0
m"
<-I
~::D
_C/)
-eo
o
NOTE: Logic probe readings taken
Up mode (Main
wise noted. Logic Probe Display L=
Low H = High P= Pulse
'"
= Open (no
light
on)
title
screen displayed) unless other-
with
computer in Power
9
::D
3:>
2
0
cO
men
....
::I:
->
....
0
m"
<~
~::D
_en
-~
o
Z56
PIIIJ
CPU BOARD A
10
1
HowardW.Sam,
'IUAiiiI.f.i3i
Photo
CPU BOARD
23
PIN
Z4
1
P 1
P 1
Z8
Zll
PI
1 P 1
PI
Z12 Z13 Z15
1
PI
1
pI
Z16
Z17
1
PI
Z2
1
PI
1
Z19
PI
Z20
1 P 1
Z38
PI
Z39
1
PI
N 1
Z22 Z23
PI
N 1
PI
N 1
255
PI
240
1
(')
CJ)
(')
CJ)
CN
CPU BOARD
22
Z42 Z43 Z25 Z44
P 1 P P 1 P
\
1
p
P
Z51
~
272
P "
Z36 Z73
PI
1
PI
1
CPU BOARD
11
1
2
3 4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
1
27
28
29
30
A
B
C
D D E
A
B
C
E
F F
G
H
G
H
::tJ
3:»
2
0
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r-~
r-C')
m",
<-4
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-CD
0
J
K
L
M
N
1
CPU
BOARD A Howord W.
12
2
3
4
SamslC;@.UUaWPhoto
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27 28
29
CPU BOARD
J
K
L
M
N
30
21
CPU BOARD GridTrace LOCATION GUIDE
Cl C2 C3 C4 C5 C6 C7
C8
C9
Cl0 B-19 Cl1 Cl2 C13 C14 C15 C16 C17 C18 C19 C20 C21
C22 C23 C24 C25 C26
C27
C28 C29 C30 C31 C32 C33 C34 C35 C36 C37 C38
C39
C40
C41
C42
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