Tektronix FG 5010 User Manual

Maintenance
- FG 5010
GENERAL
TROUBLESHOOTING
Introduction
The
front panel
error
codes
help to
isolate the
difficulties
.
After
the
trouble is
isolated ,
review the
schematics and
cir
cuit description as aids in finding the difficulty . Signatures
for the CPU , serial shift registers and some logic in the Loop
2
and Sine
Shaper
circuitry
are
included
in
this
manual .
Sev
eral
troubleshooting
techniques for
the
analog circuitry on
Loop
1 and Loop
2
boards are also
included .
Analog type
troubleshooting
techniques
are
usable on
the
Sine
Shaper ,
Output
,
Display
Driver ,
Interconnect
,
and Front
Panel
circuit
boards .
Loop 1
Troubleshooting
Remove
jumper
P1435
.
Location of
this
jumper is
shown
on
the
Adjustments
Location
illustration for
the Loop
1
board
in
the pullout
pages
at
the rear
of
this manual
.
Ground
the
collectors
of
Q1432
and Q1340
.
Connect a
variable
dc
voltage
source
( ± 1.1
V )
from ground
to the
capacitor
side
of
jumper
P1435 (
across
C1432 ) .
Connect
an
oscilloscope
to
the
emitter of
Q1332 ,
the
output of the
triangle
buffer
.
Now
vary
the voltage
source
from
approximately
+1.1
V to
-1.1
V. The
voltage
at the
oscilloscope
should
smoothly
track the voltage source changes . This proves proper oper
ation
of the
triangle
buffer .
Connect the
oscilloscope
probe
to
either
pins 13 or
14 of
U1351A
, the
level
detector
circuit
ry
. One
output is
the
complement
of the
other .
Again , vary
the
voltage
source
from +1.1 V
to 1.1
V.
Look for
a
high
to
low 400
mV
voltage
change at the
output
pins .
Satisfac
tory
operation
indicates the
level
detector is
operating
properly
. To
check
the
level
shifter
and
transistor
bridge ,
substitute a
current
meter
for the
short
from the
collectors
of Q1432 and U1340 to ground . Vary the voltage source
between
+1.1
V
and 1.1
V and
observe
the
current me
ter
. The
meter
should indicate first
one
current polarity
and
then the
other as
the
voltage
source is
varied .
Cal Mode Troubleshooting
Troubleshooting
the
frequency
control
circuits
can
also
be
done
in
the Cal
mode
. The
FG 5010
goes into
the Cal
mode
by
setting
the mode
strap on
the rear
of
the
CPU
board
( J1121
) to
the
Cal position
.
The
instrument
must
then
go
through
a
power -
on cycle
to
enter
the
Cal
mode .
The
differences between
the
Cal and
Normal
mode are :
1.
The
automatic
frequency
control
is
disabled .
The
fre
quency
D / A
is
always
set to
4000 (
decimal
) at
the
top
of
each
range .
For example
, 2.000
MHz
will
set
the
frequency
D
/ A to
4000 ,
1.000
MHz will
set
it to
2000 ,
and
200.1
kHz
will set it to 400. In the VCF mode , the frequency D / A may
be
set to zero
by
setting the
frequency to zero
.
7-14
2.
Both
frequency D / As and
both
symmetry D / As may
be
set to
zero by a
RECALL
command .
These D / As may
be
restored
by a
RECALL 1
command
or by
turning the VCF
mode
off .
3.
The automatic
range
switching in
the PH
LOCK
mode
is disabled . To select a desired frequency range or phase
lock filter , go to CONTinuous mode , program a frequency in
the
desired
range ,
then
go
to
PH LOCK
mode .
4.
The
message
delimiter
switch
on
the
rear of
the
in
strument is used
in the Cal mode
to stop the
power - on self
test
when the
first error is
detected . Set the
message
delimiter
switch to
the LF /
EOI
position to stop
the self
test
on
the first
occurrence
of an
error .
This
leaves
the
instru
ment
hardware
in the
state
where the
fault
was
detected
. To
resume
execution
of the
self
test
,
press the
ID key
.
5.
While the
SLOPE
setting is
negative , the
frequency of
the
main
loop is
measured by the
frequency control
logic on
the
Loop 2
board
approximately
every
30 ms
.
The frequen
cy
D / As
on
the Loop 1
board
are
not
changed to
correct
for
frequency
errors
.
This is
done
to
allow
for
troubleshooting
of
the
frequency control
logic
on
Loop 2 .
While the
SLOPE
setting is
positive , the
frequency
of the
main
loop is
measured
whenever
the
manual
trigger key
is
pushed
.
This is
used for
triggering
single
shot
measure
ments
by
the
frequency
control
logic
on
Loop
2.
After
each
measurement
is
made ,
the
number
of
counts
in
the
refer
ence
frequency
counters
(
U1320
and
U1322
Loop 2
) is
dis
played
on
the front
panel
readout .
The
number of
main
loop
cycles
over
which
the
measurement
is
made
can
be
calculat
ed
by
multiplying
the
frequency
setting (
in
Hertz ) by
0.005 .
The
result of
this should
then
be
rounded
off to
the nearest
integer
. If
this
number
is
exactly
half
way
between two
inte
gers , it
should
be
rounded to
the
nearest
even
integer ( i.e.
,
5.5
rounds
to 6 , and
8.5
rounds to 8. )
Loop 2
Troubleshooting
The
following
procedure
checks
the
trigger -
gate
input
amplifier
,
the
phase
detector
,
charge
pump ,
phase
lock
fil
ter
,
and
over
and under -
range
detectors .
Place
the FG 5010
in the Cal
mode . This
is accomplished
by
moving
jumper
P1121
,
located
on
the
CPU
board
, to
the
Cal
position
and
powering
up the
instrument
.
See
the
CPU
board
Adjustment
location
illustration
for the
location
of
this
jumper .
Upon
power
up ,
the
display
reads
CAL
, then
1
kHz
)
REV JAN 1982
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Tektronix FG 5010 Specifications

General

Brand	Tektronix
Model	FG 5010
Category	Portable Generator
Language	English