Radio Shack TRS-80 User manual
•
erv1ce
TRS·BD®
DT-1
Catalog Number 26-6050
CUSTOM MANUFACTURED IN U.S.A. BY RADIO SHACK, A DIVISION OF TANDY CORPORATION
TRS-80® DT-1
Manual
© 1982 Tandy Corporation
All
Rights Reserved
Reproduction or use, without express written permission
from Tandy Corporation,
of
any portion
of
this manual is
prohibited. While reasonable efforts have been taken in
the
preparation
of
this manual
to
assure its accuracy, Tandy
Corporation assumes no liability resulting from any errors or
omissions in this manual, or from the use
of
the information
obtained herein.
-----------TRS-BO
®
-----------
TRS-8S
DT-1
Service
Manual
26-6SSS
----------llad1elhaek
----------
----------TRS-BO
®
---------
---------llad1elhaell---------
___
.....,D-.T_-
...
1
________
TRS-BO
®
__
.....:i;;S~e.;:;.r.:.v.:.i~c~e~M~a;,;,,:;no=u
..
a_1
____
_
Table
of
Contents
l/Specifications
••••••••••••••••••••••••••••••••••••
5
2/Dissassembly
Instructions
•••••••••••••••••••••••••
?
3/Troubleshooting
Chart
•••••••••••••••••••••••••••••
11
4/Pr
inted
Circuit
Board
Layout
••••••••••••••••••••••
15
5/Parts
List
.
.............................
.
........
.
17
6/Schematic
Diagram
.................................
21
7/Theory
of
Operation
•••••••••••••••••••••••••••••••
25
-----------
llad1elhaell----------
- 3 -
DT-1
---~.....;;.
_______
TRS-BO
®
___
s...,e.;;.r.;..v,;;.ic;;;.;e:;;...:,M;:,:;a:,;n~u;;:a;;;,l
__
_
---------
lladme
lhaell---------
- 4 -
___
......
D
...
T._-
..
1.....
_______
TRS-BO
®
__
......
s
...
e.r
...
v
...
i
...
c
...
e...,..M
....
a
...
n_u_a_1
____
_
1/
Specifications
AC
Power
Supply
Power
Requirements
Power
Consumption
Temperature
Range
Humidity
Range
non-condensing
Size
Weight
1~5-13~
VAC,
6~
Hz
2~
watts
55
to
11~
F
(13
to
43
C)
1~%
to
8~%
relative
18.5"
x
12"
x
21"
Cl7cm
x
31
cm x
53cm)
23.4
lbs
(l~.5kg)
RS-232-C
Input/Output
============================================================
Signal
Function
Pin
#
=============================================================
PG
Protective
Ground
1
TD
Transmit
Data
2
RD
Receive
Data
3
RTS
Request
to
Send
4
CTS
Clear
to
Send
5
DSR
Data
Set
Ready
6
SG
Signal
Ground
7
CD
Carrier
Detect
8
DTR
Data
Terminal
Ready
2~
============================================================
Table
1.
-----------lladte
lhaell-----------
- 5 -
---
0
-T---
1
-------TRS-BO
®
Service
Manual
RS-232-C
Serial
Printer
============================================================
Signal
Function
Pin
#
====:========================================================
PG
Protective
Ground
1
TD
Transmit
Data
.,
.J
CTS
Clear
to
Send
5
DSR
Data
Set
Ready
6
SG
Signal
Ground
7
CD
Carrier
Detect
8
DTR
Data
Terminal
Ready
2~
============================================================
Table
2.
Parallel
Printer
Interface
==========================================
=
===============
Signal
Function
Pin
#
==
=
=======================================================
Strobe
Clock
the
data
from
the
1
processor
to
the
printer
Data
~
Bit
~
LSB
of
output
data
byte
3
Data
1
Bit
1
of
output
data
byte
5
Data
2
Bit
2
of
output
data
byte
7
Data
3
Bit
3
of
output
data
byte
9
Data
4
Bit
4
of
output
data
byte
11
Data
5
Bit
5
of
output
data
byte
13
Data
6
Bit
6
of
output
data
byte
15
Data
7
Bit
7
of
output
data
byte
(MSB)
17
BUSY
Input
to
Termnal
from
Printer
21
High
indicaGes
busy
===========================================================
Table
3.
----------ltad1elhaell----------
- 6 -
________
D_T_-_1
_________________
"TFISi-E3CJ
®
____
__.s.e_r_v_i_c_e,__M_a_n_u_a_1
______
__
2/Dissassembly
Instructions
i.
Turn
the
DT-1
upside
down
on
your
work
area.
2.
Remove
the
6
screws
from
the
bottom.
3.
Rotate
the
DT-1
rightside
up.
You
must
hold
the
top
and
bottom
section
together
during
this
operation.
Leave
room
to
the
left
for
the
top
to
rest.
4.
Lift
off
the
top
section
and
lay
it
on
its
side
to
the
left
of
the
bottom
section.
The
unit
may
be
operated
in
this
position
for
test
purposes.
Further
Dissassembly
If
desired
the
top
section
may
be
separated
from
the
bottom
section.
To
do
this
unplug
the
cable
from
the
edge
connector
and
the
grounding
lead
from
the
spade
lug
ground
connector
on
the
Video
Board.
The
top
and
bottom
sections
are
now
separate.
Circuit
Board
Removal
Follow
these
steps
to
remove
the
circuit
board
from
the
bottom
section
of
the
DT-1:
1.
Unplug
the
cables
going
to
the
video
board,
the
power
supply
and
the
keyboard.
2.
Remove
the
6
nuts
and
washers
holding
the
circuit
board
to
the
bottom
section.
3.
Unplug
the
power
indicator
cable
going
to
the
keyboard
from
the
main
circuit
board.
--------------------------------nat11elhaell-------------------------------
- 7 -
_______
D_T_-_1----------------"T~!S-EICJ®
_____
s_e_r_v_1_·c.e.....,M_a_n_u_a_1
______
__
CRT
Removal.
Be
very
careful
removing
the
CRT.
It
is
fragile,
and
could
be
dangerous
if
broken.
Never
hold
it
by
the
neck.
Follow
the
steps
below.
1.
Remove
the
plug
from
the
end
of
the
neck.
Gently
pull
straight
back.
Be
careful
not
to
bend
the
pins.
Check
to
be
sure
you
haven't
shorted
terminals
or
components
mounted
on
the
plug.
2.
Remove
the
yoke
from
the
neck
by
loosening
the
clamping
screw,
then
pulling
the
yoke
straight
back.
Be
careful
to
avoid
the
pins
at
the
end
of
the
neck
of
the
CRT.
3.
To
remove
the
anode
lead,
loosen
the
plastic
insulating
cover
from
the
CRT,
then
remove
the
lead
by
pressing
to
one
side
on
the
connector
while
gently
lifting
up
on
the
other.
4.
Remove
the
2
screws
holding
the
video
board
to
the
top
section
and
set
the
board
to
one
side
to
allow
access
to
the
CRT
mounting
studs.
4.
Remove
the
4
nuts
and
washers
from
the
mounting
studs
at
each
corner
of
the
mask.
5.
Supporting
the
CRT
from
the
body
(not
the
neck)
lift
it
up
and
back
off
the
studs.
Lay
it
on
a
soft
cloth
face
down.
6.
Finally
unhook
the
spring
and
the
two
loops
of
braid
from
the
corners
of
the
CRT.
Keyboard Removal
To
remove
the
keyboard,
1.
Take
out
the
6
screws
that
hold
the
mask
to
the
bottom
section.
2.
Lift
off
the
mask
and
the
keyboard.
3.
Unplug
the
ribbon
cable
going
to
the
main
circuit
board
and
the
grounding
spade
lug
from
the
left
end
of
the
keyboard.
See
Figure
1.
-------------------------------nad1elhaell------------------------------
- 8 -
---
0
-T---
1
-------
TRS-BO
®
Service
Manual
Figure
1.
Keyboard
Removal
Removing
the
Power
Supply
Module
To
remove
the
power
supply
module,
take
out
the
screws
holding
the
bracket
to
the
bottom
section.
Do
NOT
remove
the
nuts
from
the
top
of
the
power
supply.
Turn
the
Module
over
and
unplug
the
AC
power
cable.
----------llad1elhaell----------
- 9 -
DT-1
____
....;;;;,
_______
TRS-BO
®
___
s_e...-r..;.v.;;.i.;;.ce.;;...,;M.:,:;a:.:,n~u~a~l~--
--------
llad1elhaeli--------
-
l~
-
___
o
...
T_-_,l
_______
TRS-BO
®
Service
Manual
3/Troubleshooting
Troubleshooting
a
terminal
involves
two
steps.
Isolating
the
problem
to
the
terminal.
Creating
a
life-like
environment
for
the
terminal
to
operate
in.
Preliminary
Considerations
Before
attempting
the
steps
above,
check
system
protocol.
Are
the
Baud
rate,
parity,
character
length
and
number
of
stop
bits
correct?
Are
the
handshaking
signals
CDTR,
DCD
and
DSR}
compatible?
Are
you
connected
properly
to
the
Host?
Is
the
printer
turned
on?
If
you
have
satisfied
yourself
that
the
problem
is
with
the
DT-1,
and
not
the
Host,
connections,
or
protocol,
proceed
with
step
2
as
follows:
If
a Modem
II
is
available,
use
it
in
Local
Test
Mode
to
echo
characters
from
the
DT-1.
Set
the
Baud
Rate
at
3SS
baud
for
testing
with
a
modem.
If
a Modem
is
not
available
disconnect
the
DT-1
from
the
Host
and
connect
pins
2
and
3
together
at
the
connector
on
the
RS-232
cable,
or
at
the
connector
to
the
printed
circuit
board
Cof
the
DT-1}.
Either
method
routes
output
from
the
DT-1
back
to
input.
Keys
typed
on
the
DT-1
should
be
displayed
on
the
screen.
If
not,
check
for
handshaking
signals
that
are
holding
the
DT-1
in
a
non-transmitting
state.
From
Set-Up
Mode,
turn
off
DTR,
DCD
and
DSR
by
setting
their
switches
to
S.
The
terminal
will
then
ignore
those
signals.
-----------
llad1elhaeli-----------
-
11
-
________
D_T_-_1-----------------"TFl!3-E1Cl ®
_____
s_e_r_v
__
ic_e
__
M_a_n_u_a.........,l
______
_
Specific
Symptoms
and
Suggestions
Extra
Characters
Dis,layed
If
pressing
one
key
results
in
a
substitute
character
or
characters
on
the
screen
suspect
the
Baud
Rate.
Procede
as
follows:
Set
the
DT-1
for
Half
Duplex
from
Set-Up
Mode.
Then
press
a
key.
If
the
key
you
pressed
is
displayed
along
with
one
or
more
stray
characters,
then
the
Baud
rate
is
probably
wrong.
Wrong
cursor
Moves,
Bad
Commands,
etc.
Some
Host
systems
will
send
End-Of-File
terminating
codes
that
are
not
compatible
with
the
emulation
mode
you
are
using.
For
example,
suppose
you
are
using
the
Terminal
to
read
data
stored
in
some
Host
system.
The
cursor
jumps
suddenly
to
the
top
of
the
screen
and
begins
overwriting
data
already
present
on
the
screen.
The
DT-1
has
received
a
code
that
homed
the
cursor.
There
are
two
approaches
to
this
problem.
1.
Reconfigure
the
Host
to
match
the
emulation
mode
you
are
using.
CompuServe
and
most
other
communications
services
have
a
setup
program
that
will
modify
the
Host
for
your
terminal.
Some
systems
can
be
instructed
to
operate
in
DUMB
mode.
In
this
mode
the
Host
will
not
transmit
any
cursor
positioning
sequences
at
all.
In
CompuServe,
this
is
done
by
appending
",TTY"
to
the
user
ID.
2.
Change
emulation
modes
through
the
Set-Up
Mode
to
match
the
Host
system's
requirements.
Buzzer
ON
Continually
This
could
result
from
one
of
the
following:
The
MPU
(U-12)
is
not
working.
------------------------nat11elhaell---------------------
-
12
-
___
D_T_--
1
-------
TRS-80
®
Service
Manual
The
oscillator
is
not
working.
Check
for
7.328
MHz
at
pin
18
of
U-12.
The
Reset
Capacitor
CC-13)
is
installed
backwards
or
is
shorted.
R-22
Missing
or
open.
Some
units
may
have
8751
microprocessors
instead
of
8~5l's.
875l's
need
the
pull-down
resistor
CR-22}
to
operate.
Keyboard
Will
Not
Operate
Eliminate
the
Host,
connections,
protocol,
etc.
Check
keyboard
Cable.
Make
sure
keyboard
is
being
scanned
by
U-5.
You
must
press
a
key
to
see
activity
at
this
IC's
output,
OR
add
pull
up
to
+5
volts.
This
is
an
OPEN
COLLECTOR
circuit.
Check
for
two
or
more
keys
shorted
or
jammed
closed.
Check
for
defective
U-5
or
U-6.
FSTRW*
to
pin
1,19
on
U-6
not
present.
EEPROM
Will
Not
Retain
Data
or
Data
Stored
in
the
EEPROM
Changes.
Power
Fail
Detect
Circuitry
not
operating.
CR-1
or
Q-1
shorted;
Q-2
open.
Defective
U-25.
This
part
has
a
l~,~~~
store
cycle
life.
Parallel
Printer
Port
Will
Not
Operate
Printer.
PSTRB*
will
not
drive
a
heavy
STROBE
current
from
printer.
Add
shunt
resistance
to
ground
on
this
pin.
The
resistor
added
should
match
the
resistance
of
the
pull
up
resistor
in
the
printer.
----------lladtelllaeli----------
-
13
-
_______
D_T_-_1----------------"TFl!S-l3Cl®
_____
s.e•r•v.;....m.ic.e.-.....M•a•n•u•a--.1
______
_
Display
Will
Not
Operate
+12
Volt
power
supply
fault.
U-7
Defective.
Display
Oscillator
CU-4)
not
functioning.
U-15
Defective.
RS-232
output
Not
Functional
DTR,
DCD,
or
DSR
not
set
correctly.
U-2~
Defective.
Cable
not
connected,
or
open
wire
in
cable.
Serial
Printer
Port
will
not
operate.
DSR,
DTR,
or
DCD
Not
set
correctly.
R-18
open.
Cable
open
or
missing.
Problem
with
Video
Board,
CRT,
etc.
See
Technical
Reference
Manuals
for
similar
Model
III
Modules.
---------------------lad1elllaeli----------------------------
-
14
-
DT-1
Service
Manual
-----------TRS-BO
®
-----------
Main
Logic
Board
Solder
Side
-----------1tad1elhaeli-----------
-
15
-
DT-1
-----------TRS-80
®
Service
Manual
-----------
llad1elhaell----------
-
16
-
____
DT_-_1
________
TRS-BO
®
___
s_e_r_v_i_·
c_e_M_a_n_u_a_l
___
_
5/Parts
List
.Electrical
Parts
Capacitors
=============================================================
Component
Description
Part
Number
------------------------------------------------------------
------------------------------------------------------------
Cl
.0
.1
mf
d
Mono
S{cfv
C2
,0.1
mfd
Mono
S{cfv
C3
,0.1
mfd
Mono
S{cfV
C4
,0.1
mfd
Mono
S{cfV
cs
1.0.0.0
pf
Mon
S,0V
C6
lS
pf
disk
S{cfV
C7
lS
pf
disk
S{cfV
ca
,0.1
mfd
Mono
S.0'V
C9
,0.1
mfd
Mono
S{cfV
Cl2
1,0
pf
disk
S{cfV
Cl3
33
mfd
Electrolytic
16V
Cl4
to
C3S
,0.1
mfd
Mono
S,0'V
Integrated
Circuits
Ul
U2
U3
U4
us
U6
U7
ua
U9
Ul,0
Ull
Ul2
Ul3
Ul4
OlS
Ul6
017
018
019
U2,0'
74LS17S
Flip
Flop
74LS17S
Flip
Flop
SN74LS86N
74LS.04 Hex
Inverter
74LS14S
Decoder
74LS24,0
Inv
Octal
Buffer
8276
Video
Generator
2716
Character
Generator
SN74LS,0'8N
74LS.0.0'
Nand
Gate
74,06 Hex
Inv
Buffer
8,0Sl
Microprocessor
MC1489 Quad
Level
Converter
74LS166
Shift
Register
SN74LS161N
4-bit
counter
74LS138
Decoder
MUX
74LS74
Dual
J-K
Flip
Flop
SN74LS373N
Octal
D-Type
74LS24S
Octal
Bus
Transceiver
MC1488 Quad
Level
Converter
837-4l{cf4
837-41,04
837-41,04
837-41,04
83,0-21,0S
83,0,0'1S3
83,0',0'1S3
837-41,04
837-41.0'4
83.0'-.01.04
832-6331
837-41,04
8,02-.017S
8,02-.017S
8,02-,0,0'86
8.0'2-.0.0'fcf
4
8,02-,014S
8,02-,024,0
8,04-,0276
8,04-S716
8,0'2-.0.0'fcf8
8,02-.0fcf
.0.0'
8,0.0'-.0.0.0'6
8,04-,0,0'Sl
8,0S-.0189
8,02-,0166
8,02-.0161
8,02-,0138
8,02-,0,0'7 4
8,02-,0373
8,02-.024S
8,0'S-.0188
-----------
lladlOlhaell-----------
-
17
-
DT-1
Service
Manual
-----------TRS-80
®
-----------
U21
U22
U23
U24
U25
026-29
MC1489
Quad
Level
Converter
74LSOO
Nand
Gate
74LS240
Inv
Octal
Buffer
SN74LS373N
Octal
D-Type
X2210-30
64
x
4-bit
RAM
2114A-6
RAM
Semiconductors
CR-1
Ql
Q2
Resistors
Rl
R2
R3
R4
RS
R6
R7
R8
R9
RlO
Rll
Rl2
Rl3
Rl4
Rl5
Rl6
Rl7
Rl8
Rl9
R20
R21
R23
R24
R25
R26
R27
1N748ARL
Zener
Diode
MPS3904
NPN
Transistor
MPS3904
NPN
Transistor
330
Ohm
l/4W
5%
4.7K
x
8NTWRK
l/8W
5%
330
Ohm
l/4W
5%
470
Ohm
l/4W
5%
lK
l/4W
5%
6.8K
l/4W
5%
lK
l/4W
5%
lOK
l/4W
5%
lOK
l/4W
5%
4.7K
x
8NTWRK
l/8W
5%
4.7K
l/4W
5%
4.7K
l/4W
5%
lOK
l/4W
5%
4.7K
l/4W
5%
4.7K
l/4W
5%
4.7K
l/4W
5%
lOK
l/4W
5%
lOK
l/4W
5%
4.7K
l/4W
5%
4.7K
l/4W
5%
2K
l/4W
5%
330
Ohm
l/4W
5%
lOK
l/4W
5%
30
Ohm
l/4W
5%
100
Ohm
l/4W
5%
lK
l /
4W
5%
Miscellaneous
Electrical
Audio
Transducer
805-0189
802-0000
802-0240
802-0373
804-0210
804-1114
815-0748
811-0904
811-0904
820-7133
829-2247
820-7133
820-7147
820-7210
820-7628
820-7210
820-7310
820-7310
829-2247
820-7247
820-7247
820-7310
820-7247
820-7247
820-7247
820-7310
820-7310
820-7247
820-7247
820-7220
820-7133
820-7310
820-7030
820-7110
820-7210
849-0001
-----------
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18
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