Schematic Diagram; Schematic Diagram, Video; Wiring Diagram; Amplifier - Radio Shack TRS-80 Service Manual

4.3
TROUBLESHOOTING GUIDE
The following information
is
intended to aid service
personnel
in
troubleshooting.
SYMPTOM ACTION
1.
Printer
does not
print
with
power
switch
in
ON
position.
1.
Check power cord and
line
fuse
at rear
of printer;
depress
PRINT
switch.
2.
Printer
does not print,
but
printer
is
PR INT
ENABLED.
2.
Ensure
interface cable
at
rear of printer
is
secure.
3.
Paper Skewing.
3.
Position pin feed tractors
(26-1152) and secure locking
lever.
4.
Ribbon
tracking
problems. 4.
Ensure
that
ribbon
is
properly
installed as
described
in
Operator's Manual.
5.
Poor
print quality
(e.g.
smudging
or
light print). 5.
Adjust head penetration
as
described
in
the Operator's
Manual.
When
servicing
the
printer for
any
reason,
a brief
inspection
and
verification of the printer areas described
below
may
prevent
potential failures
in
the
future.
To
perform
this
inspection,
first
remove
the printer covers.
Then, with
power
turned
off,
check
the following
areas:
1.
Verify that the
carriage
guide bars are clean
and
free of caked-on-dirt.
2.
Verify proper
main
drive
belt
tension.
3.
Verify smooth,
free carriage
motion.
4.
Check
that the
RTP
and
EOP
switches
are
not
loose.
5.
Verify proper pin
alignment on
optional pin feed tractor.
6.
Verify
proper back
stop
pawl spring tension
in
the
line
feed clutch
unit.
7.
Verify
smooth
line
feed clutch operation.
Detailed information
on
the operation, removal, replacement
and
adjustment of each
functional
assembly
is
contained
in
Sections 2
and
3 of
this
Manual.
4.4
ENGINEERING DRAWINGS
The
following pages contain schematic, wiring
and assembly
diagrams for the
printer.
A
list
of these
drawings
is
as
follows:
FIGURE
DESCRIPTION DRAWING
NO.
4-1 Schematic Diagram,
Electronics
Board 63779105-9001
4-2
Schematic Diagram, Video
Amplifier 63703165-9001
4-3 Wiring Diagram,
Printer 63779102-9001
4-4 Primary
Voltage, Wiring Diagram 63703115-9001
4-5 Assembly
Diagram, Electronics Board 63779104-4001
4-6 Assembly
Diagram,
Video
Amplifier 63703164-4007
4-3