Maintenance—
Type
575
individual
circuits.
If
you
recognize
immediately
which
cir
cuit
is
at
fault when
a
trouble
appears,
you
can
proceed
directly
to
the
Circuit
Troubleshooting
information
without
using
the
recalibration
procedure
to
isolate
the
defective
cir
cuit.
In
such
cases,
however, you
must
be
certain
that
the
trouble
cannot
be
corrected
by
recalibration
before using
the
Circuit
Troubleshooting
information.
For
any
type
of
trouble
the
power
supplies
should
be
checked
as
one
of the
first
steps
in
the
troubleshooting
pro
cedure.
Correct
operation
of
every
circuit
in
the
instrument
depends
on
proper
output
voltages
from
the
regulated
power
supplies.
Due
to
the
circuit
configuration
employed
in
the
Type
575,
it
is possible
for
an
incorrect
power
supply
voltage
to
affect
one
circuit
more
than
the others. When
all
but
one
circuit
is
operating
properly,
there is
a
tendency
to
overlook
the
power
supply
as
a
source
of
the trouble
and
to
concen
trate
on
the circuit
where
the
trouble
apparently
exists.
In
cases
of
this
type,
valuable
time
can
be
saved
by
checking
the
power
supplies
first.
The
power
supplies
may
be checked
using
Step
1
of
the
recalibration
procedure.
WARNING
Be
careful
of
power
supply
voltages.
Under
cer
tain conditions,
they
can
be
dangerous
to
human
life.
Outputs of
the
Low
Voltage
power
supply
are
particularly
dangerous due
to
their
high
current
capabilities.
When
working
on
the
instrument
with
the
power
on,
you
should
work
with
only
one
hand
at
a
time,
being
careful
that
the
other
hand
does
not
touch
the
metal frame
to
the
instrument.
If
possible
stand
on
an
insulated
surface
and
use
in
sulated
tools
and
probes.
Circuit
Troubleshooting
This
portion
of
the
Troubleshooting
Procedure
contains in
formation
for
locating a
defective
stage
within
a
given
circuit.
Once
the
stage
at
fault is
known,
the
component(s)
causing
the
trouble can
be located by tube
and
component
substitu
tion,
voltage
and
resistance
measurements,
or by
short
and
continuity
checks.
Tube
failure
is
the most
prevalent
cause
of
circuit failure.
For
this
reason, the
first
step
in
troubleshooting
any
circuit
is
to
check
for
defective
tubes,
preferably
by
direct
substitu
tion.
Do
not
depend
on
tube
testers
to
adequately
indicate
the
suitability
of
a
tube for use
in
the
instrument.
The
cri
erion
for
usability
of
a
tube is
whether
or
not
it
works
satis
factorily
in the
instrument.
Be
sure
to
return
any
tubes
found
to
be
good
to
their
original
sockets.
If
this
procedure
is
followed,
less
recalibration
of
the
instrument
will
be required
upon
completion
of the
servicing.
If
the
replacement
of
a
defective
tube
does
not correct
the
trouble,
then
check
that
components
which are
associated
with
the
tube
have
not
been
damaged.
Shorted
tubes will
often
overload
plate-load
and cathode resistors. These
com
ponents
can
usually be
checked
by a
visual
inspection
of
the
circuit.
If
no
damaged
components
are
apparent, however,
it
will
be necessary
to
make
measurements
or other
checks
within
the
circuit
to
locate
the
trouble.
Troubleshooting
The Low-Voltage
Power Supply
Proper
operation
of
every
circuit
in
the
Type
575
depends
on
proper
operation
of
the Low-Voltage
Power
Supply.
The
regulated
voltages
must
be
within
their
specified
tolerances
for
the
instrument
to
remain
within
calibration.
For
no output voltage
If
the
pilot lamps
and
the
fan
do
not
operate
when
the
power
switch
is
turned
on,
check
the
power
switch,
the
line
fuse,
and
the
line
voltage.
If
your
instrument
is
wired
for
234-volt
operation,
also
check
the
thermal
cutout
switch.
(In
an
instrument
wired for
117-volt
operation,
the
fan
will
run
even
though
the
thermal
cutout
switch
may
be
open). If the
fuse
is
not
blown
and
the
line
voltage
is
correct,
check
the
primary windings
of
the
power
transformer.
If
the
pilot
lamp and
the
fan
operate
correctly,
the
primary
circuit
of
the power
transformer
may
be
assumed
to
be
op
erating
normally.
The
trouble
then
lies
somewhere
in
the
secondary
circuits.
When
only
one
of
the
outputs
of
the
Low-Voltage
Power
Supply
is
zero,
the
trouble
is
probably
due
to
a
defective
rectifier,
series
regulator,
or
power
transformer
secondary
winding.
To determine
which
circuit
element
is
defective,
measure
the
secondary
voltage of
the
transformer
and
the
voltage
at
the
output
of
the
rectifier.
The
cause
of
the
trouble
can
be
determined
by
the
voltage
readings
obtained.
For
failure of a power supply to regulate
at the
proper voltage
If
any
one
or
all
of
the
supplies
fail
to
regulate
at
the
proper
voltages, first
check
the
line voltage.
The
supplies
are
designed
to
regulate
between 105 and
125
volts
(or
210
and
250
volts)
with
the
design
center
at
117
volts
(or
234
volts),
rms.
Improper
line
voltage
may
cause
abnormal
operation
of
one
or
all
of
the
power
supplies.
The
+100-
and
+300-volt
power
supplies
are
dependent
upon
the
—150-volt
power
supply
for
regulation,
and
con
sequently
a
change
in
the
regulation
point
of
all
the
supplies
is
indicative
of
a
defective —150-volt
supply.
If
the
output
voltage
of
the —150-volt
power
supply
is
off
only
a
small
amount,
it
may
be possible
to
readjust
the
—150
ADJ
con
trol
for
the proper
voltage.
In
any
event
it
will
be
necessary
to
recalibrate
the instrument when the
trouble
is corrected
and
the
output
voltages
are
again
normal.
In
case
a
single
power
supply
should
fail
to
regulate
at
the proper
voltage
check
the
following:
1.
Line voltage
2.
Transformer
secondary
voltage
3. Output
voltage
of
the rectifier
4.
Tubes
5.
Loading
Important
power
supply
voltages
are
marked
on the
power
supply
schematic
diagram.
These
voltages
may
be
used
to
4-4
Summary of Contents for 175
Page 4: ...VWTICM OINltAlO TRANSISTOR CUM TRACfR UB l COUlClO r hokizoniai VCKIJ O lUnK Hix M Type 575 z ...
Page 6: ...NOTES ...
Page 26: ...NOTES ...
Page 48: ...NOTES ...
Page 54: ...Recalibration Type 575 C706 Fig 5 3 Left Side View 5 6 ...
Page 56: ...NOTES ...
Page 100: ...INPUT AMPLIF1E ...
Page 104: ...TYPE 575 TRANSISTOR CURVE TRACER ...
Page 108: ...OSCILLATOR 4OOV UNREG TYPE 575 TRAN5I5TOR CURVE TRACER AB ...
Page 115: ... 300 ...
Page 119: ...Type 175 Tent S N 570 PARTS LIST CORRECTION Change to Q233 151 0137 00 2N21U8 MIO 298 1165 ...