Radio Shack Quick Printer II Technical Reference Manual

5 POKE 65312,2
10 FORX=0TO10:
NEXTX
15 POKE 65312,0
20
FORX=0TO10:NEXTX
25
GOTO 5
Run the
program
and check
pin 2 of
U15;
a
switching
TTL
waveform should
be present.
Pin 6
of
U15
should
have the
same waveform
except
that it
will be switching
from +11 volts
to
-
11 volts.
Also check
pins 4
and
6
of
U14.
These pins
should have
the same
waveform
switching from to
+10
volts.
The
outputs of U14,
pins 1
and
2
should
show the
original
TTL
signal when the
test
program is
running.
POWER SUPPLY
If
you
have
a
power supply
problem,
usually
only one of the
four supply voltages will be bad.
However the
+5
volt supply
is powered by the
+12 volts supply, so
a bad
+12
volt supply
will also cause the
+5 volt supply to fail. Anytime you have a
supply that is at zero volts, you
should measure
the
resistance
between ground
and that supply (with
power off).
This will
quite
often show
that you have
a
short to
ground. Please
note
that the
+5
volt supply has an
overvoltage diode, CR17,
which
will automatically short
to ground in the case
of an over-
voltage
condition on the
+5
volt power supply.
If the
problem is
not an
external
short to
ground, refer
to
Figure
1
and check
the
voltages
along
the
affected
power
supply.
If
the voltage
is
bad
at one
output of
CR11,
the
reg-
ulator
or the filter
capacitor
is
bad. If
both voltages
are
bad
then
CR11
is
faulty.
Check
that
CR11
has the correct
input
voltage
from
the
transformer.
If
the voltage
is correct
at the
input
to
the
regulator
and
the
output
is not
shorted,
then the
regulator
is
bad.
The
+5 volt
supply is
more
complex than
the
other
supplies.
However, you
may use
the same
troubleshooting
method
as
with
the other
supplies.
Check the
voltage
from
the input to
the
output
of the
supply
until you find
the
point
where the
voltages
are
wrong. This
will usually
point to
the bad
device.
A
faulty
+5
volt
supply may be
caused by U13, Q2,
or Q3.
If the
+5 volt supply
was shorted to
ground by CR17
then
there is also a
problem with the
regulator
circuit. To
correct
this, remove CR17
and break
the +5 volt
line while
trouble-
shooting the
supply. Removing
R66
will break
the +5
volt
output
line.
46

Radio Shack Quick Printer II Specifications

General

Brand	Radio Shack
Model	Quick Printer II
Category	Desktop
Language	English