Tektronix TG501 User manual

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TABLE OF CONTENTS
Page
LIST
OF
ILLUSTRATIONS ... .............. ............ ................. . .

ii
TG 501
REVD AUG 1980

i
Section 1 Specification . ... ......... ............ ................. . .
1-1
Section 2
Operating Instructions ......... ........... ................. 2-1
WARNING
THE FOLLOWING SERVICE INSTRUCTIONS ARE FORUSE BYQUALIFIED
PERSONNEL ONLY . TO AVOID PERSONAL INJURY, DO NOT
PERFORM
ANY SERVICING OTHER THAN THAT
CONTAINED IN OPERATING
INSTRUCTIONS UNLESS YOU ARE
QUALIFIED
TO DOSO .
Section 3
Theory
of
Operation . . ........... ........... ............... 3-1
Section 4 Calibration Procedure . ............ ........... ............. .
4-1
Performance Check
. . . ......... ........... ..... . . . ...... 4-1
Adjustment Procedure
. ......... ........... .... .... ...... 4-5
Section s
Maintenance ........ ........... ........... ..... ... ...... 5-1
Section 6 Options
............... ......... ............. . ..... ..... 6-1
Section 7 Replaceable Electrical Parts ... ........ . . ................. . . .
7-1
Section 8 Diagrams and Illustrations ..... ........... ...................
8-1
Section 9 Replaceable
Mechanical Parts
. . ....... .
. . .................... 9-1
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TG 501
LIST O F
ILLUSTRATIONS
Figure
No .
Page
2-1
Plug-in installation and removal ...... ......... ................
2-1
2-2 Controls and Connectors
. . ........... .......... ............
2-2
2-3 Timing
error of time base ... .............
........ ...........
2-3
2-4 Measuring timing error of
time base . .......... ............ ..... 2-3
2-5
Markers approximately at pulse duration and
period
................
2-4
2-6 Measuring pulse duration .......... ..........
...............
2 - 4
2-7
Measuring pulse period ..... .......... . . .........
.........
.
. . 2-5
3-1
Functional Block Diagram of schematic diagrams
1 and 2 circuitry . . .... 3-3
3-2 Functional
Block Diagram of
schematic diagram 3 circuitry . ..........
3-5
3-3 Functional
Block Diagram of schematic diagram 4 circuitry ...........
3-7
3-4
Functional Block Diagram of
schematic diagram 5 circuitry ...........
3-9
5-1
Semiconductor device lead configuration
found in the TM 500 family .... 5-5
5-2
Location of jumpers and integrated
circuits required for clock options . . . 5-9
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TG 501
OPERATORS SAFETY SUMMARY
The general safety information in this part
of
the summary
is for both operating and servicing personnel . Specific
warnings and cautions will be found throughout the
manual where they apply, but may not appear in this
summary .
power cord into a properly wired
receptacle before
connecting to the product input or output terminals . A
protective ground connection by way of the grounding
conductor in
the
power cord is essential for safe opera-
tion .
Terms In This Manual Danger Arising From Loss of Ground
CAUTION statements identify conditions
or
practicesthat
could result i n damage to the equipment or other property .
WARNING statements identify conditions or practices
that could result in personal injury or loss of life .
Upon
loss
of
the protective-ground connection, all
accessible conductive parts (including knobs and con-
trols that may appear to be insulating) can render an
electric shock .
Terms As Marked on Equipment
CAUTION indicates a personal injury
hazard
not im-
mediately accessible as one reads the marking, or a
hazard to property including the equipment itself .
Use the Proper Power Cord
Use only the power cord and connector specified
for
your
product .
DANGER
indicates a personal injury hazard immediately
accessible as one reads the marking .
Symbols As Marked on Equipment
DANGER - High voltage .
Protective
ground
(earth) terminal .
ATTENTION - refer to manual .
Use only a power cord that is in good condition .
Refer cord and connector changes to qualified service
personnel .
Use the Proper Fuse
To avoid fire hazard, use only the fuse of correct type,
voltage rating and current rating as specified in the parts
list
for
your product
.
Power Source
Refer fuse replacement to qualified service personnel .
This product is intended to operate from a power source
that will not apply more than 250 volts rms between the
supply conductors or between either supply conductor
and ground . A protective ground connection byway of the
grounding conductor in the power cord is essential for
safe operation .
Do
Not Operate in Explosive Atmospheres
To avoid explosion, do not operate this product in an
explosive atmosphere unless it has been specifically
certified for such operation .
Grounding the Product
This product is grounded through the grounding conduc-
tor of the power
cord . To
avoid
electrical shock, plug
the
Do Not Operate Plug-In Unit Without Covers
To avoid personal injury, do not operate this product
without covers or panels installed . Do not apply power to
the plug-in via a plug-in extender .
@ AUG 1980
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Do Not Service
Alone
SERVICE SAFETY SUMMARY
FOR QUALIFIED SERVICE PERSONNEL
ONLY
Refer also to the precedingOperators
Safety Summary .
Do
not perform internal service or adjustment of this
product
unless another person capable of rendering
first
aid and resuscitation is present .
Use Care
When Servicing With Power On
Dangerous voltages exist at several points in this product
.
To avoid personal injury, do not touch
exposed connec-
tions andcomponents
while power is on .
@ AUG 1980
TG 501
Disconnect
power before removing protective panels,
soldering, or replacing components .
Power Source
This product is intended to operate from a power
source
that will not apply more
than 250 volts rms between the
supply
conductors or between either supply conductor
and ground . A protective ground connection
byway
of
the
grounding conductor in the power cord
is essential for
safe operation .
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TG 501 Time Mark
Generator
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Description
The TG 501 is a general purpose Time Mark Generator
plug-in
designed to operate in a TM 500 Series Power
Module . A Variable Timing Readout provides a simple but
accurate
means
of measuring timing errors over t7 .5%
minimum range . Since many specifications are given in
percentages, the error readout eliminates the need for
computations and, additionally, lessens parallax dis-
crepancies
.
Marker selection from 5 s through 1 ns in a 1, 2, 5,
sequence is available
. 5 s through 10 ns markers are
selected by a rotary switch . 5, 2, and 2
ns modified sine
REV D SEP 1980
SPECIFICATION
INTRODUCTION
Table 1-1
ELECTRICAL CHARACTERISTICS
Section 1-TG 501
waves are selected by self-canceling push-buttons
when
the rotary switch is in the 521n position .
All outputs are available at the
front-panel connectors,
or by modification at the interface connector,
located at
the back of the plug-in, and the TM 500 Series Power
Module .
Power supplies are current limited
. The 5 V supply is
over-voltage protected to avoid
damage to the integrated
circuits .
Characteristics Performance Requirements Supplemental
Information
Markers
5 s through 1 ns in a 1, 2, 5 5 s through 10 ns are selected
sequence .
by a rotary switch . 5 ns, 2 ns,
and 1
ns are push button selected
modified sine
waves .
Marker Amplitude
>1 V peak on 5 s .through 10 ns
markers . >750 mV peak-to-peak into
50 O on 5 ns and 2 ns markers
.
>200 mV peak-to-peak into 50 S2
on 1 ns markers .
Trigger Output Signal
Slaved to marker output from 5 s Amplitude same as marker amplitude .
through 100 ns . Remains at
100 ns
for all faster markers .
Internal Reference Standard Option 01
Crystal
Frequency 1 MHz 5 MHz
Stability (0°C to +50°C) Within 1 part Within
5 parts
after 1/2 hour warm-up in 10 5 in 10'
Long-Term Drift
1 part or less 1 part or less
in 10 5 per in 10' per
month month
Setability Adjustable to Adjustable to
within 1 part within 5 parts
in 10' in 10 9
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Specification-TG
501
Table 1-1 (cont)
Table 1-2
ENVIRONMENTAL
CHARACTERISTICS
REVD
AUG 1980
Characteristics
Performance
Requirement
Supplemental
Information
External Reference
Input
Lift pin
3 of U350 from socket
;
(Available Only
if U50 and
IC
and jumpers for 5 or
10 MHz,
jumpers are
installed and U100
1 MHz external
reference requires
is removed)
jumpers .
Acceptable Frequencies
1 MHz, 5
MHz, or 10 MHz .
Internally hard wired so
output
frequencies
counted down to 1 MHz .
Input
Amplitude
Must
be TTL,
compatible .
Error
Readout Range
To±7
.5% .
Timing
Error
Measurement
Device under
test error is
Example : If DUT Timing
error reads
Accuracy
indicated
to within one
least 3
.0% slow, the absolute
accuracy
significant digit (i .e .,
to
will be between
2 .9%and 3 .1%
within one
displayed count) .
slow .
Characteristics
Description
Meets
MIL-T-288008, class 5 .
Temperature
Operating
0° C to +50° C
Non-operating
-55° C to
+75° C
Humidity
95%
RH, 0°C to 30°C
Exceeds MIL-T-288008,
class 5 .
75%
RH, 30° C to 40° C
45% RH, 40° C to
50° C
Altitude
Exceeds MIL-T-288008,
class 5 .
Operating
4 .6
Km (15,000 ft)
Non-operating
15 Km (50,000
ft)
Vibration
0 .38
mm(0 .015 inch
peak-
Exceeds
MIL-T-28800B, class
5,
to-peak,
5 Hz to
55 Hz,
when
installed in qualified
75 minutes .
power modules .
Shock
30 g's
(1 /2 sine)
11 ms
Meets
MIL-T-288008, class 5,
duration, 3
shocks in each
when
installed in qualified
direction
along 3 major
axes,
power modules .
18 total
shocks .
Bench Handling
12
drops from 45°,
4 inch
Meets
MIL-T-2880013, class 5 .
or
equilibrium,
whichever
occurs first .
Transportation
Qualified
under National
Safe Transit
Association
Preshipment Test
Procedures
1A-B-1
and 1A-B-2 .
EMC
Within limits of
MIL-461A, and
F .C
.C
. Regulations,
Part 15, Subpart
J,
Class A .
Electrical
Discharge
_ t20
kV maximum c harge
applied to
instrument case .
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Table 1-3
PHYSICAL CHARACTERISTICS
Specification-TG 501
REV C AUG 1980
Characteristics Description
Finish Anodized aluminum panel and chassis
Net Weight
2 lbs ., 4 oz . (1 kg .)
Dimensions 2 .633 in . (66 .8 mm) w
x
11 .240 in . (285 .3 mm) d
x4
.961 in . (125 .9
mm) h
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Section
2-TG 501
OPERATING
INSTRUCTIONS
Installation
The TG 501 is calibrated
and ready for use when
received .
Referring to Fig . 2-1, install the Generator and
turn on the Power
Module . Check the front-panel of the
Generator to
see that the knob skirt is lighted . The TG
501
is
designed to operate in any compartment
of a TM 500
Series Power Module . Refer to the
Power Module Instruc-
tion Manual for line
voltage requirements and Power
Module operation .
Turn the
Power Module off before inserting the plug-
in
;
otherwise,
damage may occur to the plug-in
circuitry .
CONTROLS AND CONNECTORS
Refer to the Controls and
Adjustments page for front-
panel controls,
connectors and indicator descriptions .
MARKER
Control
ORotary switch selects individual
marker intervals from
5 s to 10 ns . Set to 521n position
when using push buttons
for 5 ns, 2 ns and
1 ns . Readout Display is turned off in
521n
position .
Fig . 2-1 . Plug-in installation and removal
.
REV C AUG 1980
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Operating Instructions-TG 501
Fig . 2-2 . Controls and Connectors .
5 ns, 2 ns AND
1 ns PUSHBUTTON
(i)Self-canceling
pushbuttons select modified sinewaves
for 5, 2, and 1 ns when MARKER control is in 521n
position . 1 ns
marker has a separate output connector .
These aare not variable .
TRIGGER OUT Connector
OProvides trigger pulses slaved to MarkerOutput from
5 s through 100 ns . Remains at 100 ns for all faster
markers . Pulse amplitude is >_1 V into 50 0 .
MARKER OUT
Connector
O
Provides positive markers of >1 V peak amplitude into
50 S2 for 5 s through 10 ns selected by
MARKER Control
rotary switch . Provides markers of _>1 V peak-to-peak
amplitude into 50 S2 for 5 ns and 2 ns modified sine waves,
selected by self-canceling push buttons
when MARKER
Control is
in 521n position .
VARIABLE TIMING Control
O6 Concentric with MARKER Control switch . Markers are
calibrated when center button is pushed in allowing
selection as indicated by the lighted knob skirt . When
center button is out, output timing is fast or slow by the
percentage
indicated
on the
Readout Display .
FAST-SLOW Indicators
Light when variable timing control is used . 'Fast' lights
when timing is faster than the standard indicated by
lighted knob skirt . 'Slow' lights when timing is slower .
Percentage faster or slower is read from VARIABLE
TIMING Readout .
VARIABLE TIMING Readout
Indicates timing variation
from standard timing . First
digit is in percent units, second indicates one-tenth
percent units .
OPERATING MODES
Calibrated Mode
When the center-button of the VARIABLE TIMING
Control is pushed in, the MARKER Control selects
calibrated marker intervals from 5 s to 10 ns, indicated by
the lighted knob skirt . To select 5, 2, or 1 ns modified sine
wave markers, set the MARKER Control to 521 n position
and press the desired pushbutton .
Variable
Timing
Mode
When the center button of
the VARIABLE TIMING
Control is out, output timing is faster or slower than the
calibrated marker to the percentage indicated by the
VARIABLE TIMING READOUT Display and the FAST-
SLOW
Indicator lights . 5, 2, and 1 ns push-button con-
trolled modified sine waves are not variable and the
Readout Display is turned off when the
MARKER
Control
is in the 521n position
.
1 ns
ONLY Connector
OProvides _>0 .5 V peak-to-peak amplitude into 50 S - 2 of
1 ns modified sine wave selected by the 1 ns push button
when MARKER Control is in 521n position
.
Readout Display Test
To check
the
operation of
the display LED's (Light-
Emitting Diodes), press the center button of the
VARIABLE TIMING Control (push in firmly) . All LED
segments should light, displaying 8 .8 in the Readout .
2-2
REV C AUG 1980
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Operating Instructions-TG
501
TYPICAL APPLICATIONS
The TG
501 can be used for many applications
not
described in the manual . Use the
following examples to
become familiar with the
TG 501's VARIABLE TIMING
READOUT . Contact
your Tektronix Field Office or
representative for making specific measurements
with this
instrument .
Time Base Measurements
To accurately
determine the timing error of atime base :
1 . Connect the MARKER OUT of
the
TG
501 to the
Vertical Input of the oscilloscope .
Usea50 Qcoaxial cable
terminated into 50 0 .
2 . Connect the TRIGGER OUT of the TG
501 to the
External Trigger Input of thetime
base . Use a 50 S2 coaxial
cable terminated
into 50 O .
3 . Select external trigger source on the time
base .
Fig . 2-3 . Timing error of time base .
4
.
Select,
for example, the 1 us sweep rate of
thetime
base .
5 .

Setthe MARKER Control rotary switch of TG
501 to
1 /is .
6 . Make sure the center button of
VARIABLE TIMING
Control, concentric with the
MARKER Control, is out
(Variable Timing Mode) .
7 .

Usethe Horizontal Position
control of thetime base
to make the first time mark coincide
with thefirst graticule
line on the oscilloscope .
See Fig . 2-3 .
8 . Rotate the VARIABLE
TIMING knob until all time
markers coincide
with graticule lines on the oscilloscope,
as
shown in Fig . 2-4 .
9 . Either the FAST or SLOW
Indicator will light
showing whether the time base is
faster or slowerthan the
calibrated
markers
of
the TG 501 . Read the percentage of
error from the VARIABLE TIMING READOUT Display .
Pulse Generator Measurements
Rotate VARIABLE TIMING
knob until
all markers coincide
with graticule lines
.
1576-05
Fig . 2-4 . Measuring timing error of time base .
2 . Connect the MARKER OUT of the TG 501 to one
channel of the dual-trace oscilloscope . Use a50
S2 coaxial
cable terminated in 50 S2 .
To accurately determine pulse duration or
period of a
Pulse Generator :
1 . A dual-trace oscilloscope is required . Select
alter-
nate mode .
3 .
Connect the Output of the pulse generator to the
other channel of the dual-trace, using a50 S2 coaxial cable
terminated in 50 0 .
REV E AUG 1980
2- 3
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Operating Instructions-TG 501
Align
first time marker
with
beginning of Pulse
Waveform .
One
cycle of a pulse in
10 divisions of the grati-
cule .
Time marker at Pulse
Dura-
tion . (approximate)
Peaks of time markers
at
50%
Amplitude of pulse .
Time marker at Pulse
period . (approximate)
1576-06
Fig . 2-5 .
Markers approximately at pulse duration and period .
4 .

Set the time/div switch to display 1 cycle of
a pulse
in 10 divisions of the
graticule on the oscilloscope, as
indicated in Fig . 2-5 .
11 . Read the VARIABLETIMING READOUT Display
and check the FAST-SLOW Indicators as described
in
step 9 to find the percentage of
error from standard timing .
5
.
Use
the MARKER Control switch of the TG 501 to
display one time marker approximately at pulse duration
andone at pulse period .
Alignthe first time marker with the
beginning of pulse wave-form . See Fig . 2-5 .
6 . Select Variable
Timing Mode on the TG 501
(VARIABLE TIMING Control center button out) .
7 .

Usethe Vertical Position control of the oscilloscope
to set the peaks of the time markers at 50%
amplitude of
the pulse shown in Fig .
2-5
.
8 . To check pulse duration, rotate the
VARIABLE
TIMING knob until time
marks coincide with pulse
duration, as
shown in Fig . 2-6 .
9 . Either the
FAST
or
SLOW Indicator will light,
showing whetherthe pulse duration of the pulse generator
is faster or slower than the
calibrated time mark of the
TG 501
. Read the percentage of error from the VARIABLE
TIMING READOUT Display .
10 . To check pulse
period, rotate the VARIABLE
TIMING knob
until time marks coincide with pulse period .
See
Fig . 2-7 .
Rotate VARIABLE TIMING
knob until timemarker coincides
with pulse duration .
Fig . 2-6 . Measuring pulse
duration .
1576-07
2-4
REV H DEC 1980
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OperatingInstructions-TG 501
Rotate VARIABLE TIMING
knob until time marker coincides
with pulse period .
Save and re-use
the package in which your instrument
was
shipped . If the original package is unfit for use or
not
available, repackage the instrument as
follows :
1 . Obtain a
carton of corrugated cardboard having
inside
dimensions of no lessthan six inches morethanthe
instrument dimensions ; this will allow for
cushioning .
Refer to the following table
for carton test strength
requirements .
2 . Surround the instrument
with polyethylene
sheeting to protect the
finish of the instrument .
3
.
Cushion
the instrument on all sides by
tightly
packing dunnage or urethane foam
between carton and
instrument, allowing three inches on
all sides .
4 .

Seal carton with
shipping tape or industrial stapler .
1576-05
Fig . 2-7
. Measuring pulse period .
SHIPPING
CARTON TEST STRENGTH
REPACKAGING
FOR SHIPMENT
If the Tektronix
instrument is to be shipped to a
Tektronix Service Center for service or repair, attach
atag
showing : owner (with address)
and the name of an
individual at your firm that
can be contacted, complete
instrument serial
number and a description of the service
required .
REV G DEC 1980
2-5
Gross Weight (lb) Carton
Test Strength (Ib)
1-10
200
10-30 275
30-120
375
120-140
500
140-160
600
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1 MHz Crystal Reference and Enable Gate
THEORY OF
OPERATION
DIAGRAMS 1
& 2
The reference frequency is
supplied by the 1 MHz
crystal reference
circuitry of Y100, U100 and U350A . The
output of the crystal
reference circuit is supplied to pin 12
of
U110D, which is part of the enable gate circuit . The
enable gate circuit, which determines
whether the 1 MHz
crystal referenceorthei
MHz variable clock is connected
to
the phase lock loop, is composed of U110A, U110B,
U1
10D, and U1 15D . When the VARIABLE TIMING (OUT)
knob is pushed in and locked, a low is on
pin 11 of U1 10D,
allowing the crystal reference
oscillator to be available at
pin 13 of U1 10D
. A low is also created at pins 12 and 13 of
U1 15D,
resulting in a high at pin 11 of U1 15D and at pin 3 of
U1
10A . The high at pin 3 of U1 10A causes a low at
pin 5
of
U1 10B, which allows U1 10B to pass the
crystal reference
oscillator signal to pin
1
of
U230A .
100 MHz
Voltage Controlled Oscillator and Dividers
The voltage controlled oscillator (VCO) iscomposed
of
an astable multivibrator
(Q280-0285-Q290), an etched
capacitor, and
Q272, which supplies the charge current
for the etched circuit board capacitor . U290D acts as
a
buffer for the VCO . The NOR output of
U290D is
connected to the Divide-By-Five
Counter . The +5 counter
contains U31
OA, U31 0B, and U315A . The output of the= 5
counter is translated from ECL into
TTL
logic
levels by
Q330, then supplied to =2 counter
U320 .
The output of =2 counter U320 is supplied to the
input
of U325 . The output, pin 11 of
U325 is applied to another
=2 counter
(U225 pin 12) . The Q output of U225 is
supplied to pin 5 of
U230B .
U230A pin 1 receives 1 MHz from either
the crystal
reference or the variable clock .
U230B pin 5 receives the
counted down (=100) 100 MHz signal from
the VCO . Pins
9 and 12 of U230 go high if
the negative edges of the input
signals
coincide ; this occurs when the 100 MHz VCO is
operating on frequency . The high inputs
to U235A
produce a low output that
clears U230A and U230B . The
transition to a low that occurs
at pin 12 of U230A is
integrated by
R231 and C231 ; the transition to a high level
that occurs at pin 8 of U230B is integrated by R239 and
C239 . The two integrated output
levels are summed by
R234 and R239 .
This summation is then fed to the negative
input
of
the loop amplifier/filter .
REV A AUG 1980
Out-of-Lock Detector
Section 3-TG 501
The input
signal to the loop amplifier/filter is amplified
and inverted by
operational amplifier U250 . The output of
U250 is
kept from changing rapidly by C250
and C251 .
VR250 level-shifts the output of U250 to
a level that can be
used to control the current
flow through Q272 .
Frequency
Control of the 100 MHz Oscillator
Assume that
the frequency has been correct up to this
cycle, and
that pins 9 and 12 of U230 are low . When the
100 MHz
VCO frequency is slower than 100 MHz
the
negative edge to the phase comparator will toggle
U230A
first . This results in a high at
pins 8 and 12 of U230 and a
more negative voltage
at the output of U250 . This more
negative
voltage causes Q272 to conduct harder, which
allows the etched circuit board capacitor to
charge more
quickly, thus increasing the
oscillator frequency .
Again assume that the frequency has been correct
up to
this cycle, but this time the VCO is faster
than 100 MHz .
The negative edge of the
next cycle will toggle U23013 first,
resulting in
a low at pins 8 and 12 of U230 . This in turn
causes
a more positive voltage at the output of
U250,
which reduces the conduction to Q272 . The
etched circuit
board capacitor now requires longer to
charge since its
available charging current
has been reduced by Q272, and
the frequency
is decreased .
Ground from the cam switch for all the marker output
enable logic gates is via Q270 . If the 100
MHz VCO is
running slow (out of specifications),
the voltage at the
output of the loop
amplifier/filter operational amplifier
Q250 will be low
. This low voltage will turn on Q255 and
Q260, which will turn off Q270, stopping the marker
output .
On the other hand,
if the 100 MHz VCO is running fast
(out
of specifications), the voltage at the output of U250
will be high . This high voltage will turn
off normally
conducting Q54,
which in turn will turn off Q270, breaking
the ground on
the enable logic gates . Without ground
there is no marker output .
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Theory of
Operation-TG 501
20 ns and .3 ,us
Divide-By-Two
Counters
The 20 ns
=2 counter
contains U315B, U290B
and
U290A . The input to the
counter is the output
of the 100
MHz VCO . The 20 ns
markers from the
=2 counter are
coupled to enable
gate U300B .
The
.2,us =2 counter is
part of U325 . The
=2 counter
output
is pin 12 of the
integrated circuit,
which issupplied
to
enable gate U330A
.
10 ns,
20 ns, or 50 ns and .
1 ,us, .2 ps, and .5
/is
Enable Gates
Enable
gatesforthe 10 ns, 20
ns, and 50 ns
markers are
U3000,
U300B, and U300A
respectively,
while the enable
gates for the .1 us, .2
jus, and .5,us
markers are U330C,
U330A, and
U335A-U335B
respectively . U335C is an
OR
gate that
couples the selected .1
Ns, .2 us, or .5
ors markers
to the
decade dividers .
1 MHz
Variable Clock
The
1 MHz variable
clock circuit is an
emitter-coupled
astable
multibibrator
. Temperature
compensation tran-
sistor 0120, which is
the same type of transistor as
Q130
and Q135, establishes
the power
supply voltage for
the
multivibrator .
Q130, Q135, and
0140 arethe
multivibrator
transistors .
Q130 controls the
charge current
availableto
timing
capacitor C127
. VR140 provides
level shifting for
the Q130 base voltage .
R135 controls
the frequency of the
multivibrator by
controlling the
conduction of Q135 .
The
lower end of
R135 is the higher
frequencyend
while the
top
end reduces the
frequency . R145
Variable Timing
Center, is used to
set the frequency of
the multivibrator to
1 MHz when
R135 is set to
its mechanical
midrange
position .
Phase
Comparator and Fast-Slow
Led's
1 MHz is fed to pin
1
of
U150A by
either the crystal
reference or the
variable clock .
The 1 MHz crystal
reference is fed to
pin 5 of U150B
. Pins 12 and 9 of
U150
will go high
if the negative edges
of the two
1 MHz input
signals
coincide . This occurs
when the variable
clock
frequency
is 1 MHz . With
these inputs
high, U115A
produces
a lowthat clears
U150A and U150B
. The low now
at
pin 9 of U15013
and the high now
at pin 13 of U1 50A
are
summed by R152
and R153 .
The output of the
summing
resistors
i
s
then fed tothe
negative input of am plifi
er U 160 .
The input signal to
U160 is
amplified and inverted .
The
output of U160
is kept from
changing rapidly by
C160 . The
slow
change in the output
of U160 causes
it to be an
apparent do level . If
U115B has been enabled
byreleasing
the VARIABLE
TIMING (OUT)
control, the output voltage
level of
U160 is applied to
the junction of
DS170 and
DS172 .
3-2
Assume that the
frequencyhas been
correct up to this
cycle, pins 9 and
12 of U150 are
low . When the 1
MHz
variable
clock frequency is
slower than 1 MHz,
the
negative edge to the phase
comparator will toggle
U150B
first .
This results in a
high at pins 9 and 13 of
U150 and a
more positive
voltage at the output of
U115B . This more
positive voltage
causes DS172
to conduct and
become
illuminated
.
Agai n
assume that the frequency
has been correct
up to
this
cycle, but this time
the 1 MHz variable clockfrequen-
cy
is faster than 1 MHz .
The negative edge of
the next
cycle will toggle
U150Afirst, resulting
in a lowat pins 9and
13 of U150 .
This in turn causes a
more negative voltage
at
the output
of U1 15B, which
results in the conduction
and
illumination of DS170 .
Digital Mixer
and Counter
The 1 MHz Crystal
Reference is counted
down by a
factor of 20,000 (2
times 10`) using decade
counters U220,
U218, U212,
and U210 and flip-flop
U215A . The resultant
50 Hz
gate frequency (20
ms gate period) available at
the
outputs
of U210 is used to
control the display time
of the
VARIABLE TIMING %
LED . Pin 11 of
U210 is the =5
output ; pin 12 is the
=2 output . Thetwo
outputs of U210
are ANDed by
U180D to produce a2
ms pulse, which is
used to clear
BCD counters U185
(0 .01% digit, which is not
displayed), U195 (0 .1% digit)
and U200 (units %
digit) .
The 1
MHz Crystal Referenceand
the 1 MHz
variable
clock output
frequencies
are compared by
digital mixer
U215B, with only the
frequency difference of
thetwo input
frequencies appearing
at the output . The
output of U215B
is ANDed in U180C
with the inverted
=2 output (10 ms
wide gate) of
U210 . The output of
U180C goestothefirst
of
the three BCD counters
.
The 2 ms output pulse
of U180D
and the 10 ms output
pulse of U115C go
to NOR gate
U110C . The output of
U110C
(which is an 8 ms
pulse that determines
LED
display
time) is one input to
AND gate U180B . The
other
input to
U180B must be a
high from U235B to
enable
U180B
and cause the
LED display to be
unblanked . A high
out of U235B is
caused by either pressing
the VARIABLE
TIMING %
control fully in to
check the LEDs,
or by
releasing
the VARIABLE
TIMING % control to
its out
position . The low to pin 5 of
U235B in the out
position of
the VARIABLE TIMING
% control is from
pull-up resistor
R450 via CR115
and inverter U1
15D . In the 521n position
of the
MARKER Control, the
cathode of CR115
is con-
nected
to ground via
S350 to disable the variable
timing
circuit, since the
1 ns, 2 ns, or 5 ns
markers are not
variable .
REV B AUG 1980
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Theory of
Operation-TG 501
VARIABLE

a
U210,U215B
TIMING _
U180D,U115C
(OUT)
1 MHz
VARIABLE
CLOCK
0120, 0130
Q135,0140
U 110C, U 180C
U235B,U180B
U185, V 190B,
U195, U200
Fig . 3-1 . Functional block diagram of
schematic diagrams 1 and 2 circuitry .
-----J 1576-12
REAR
INTERFACE
CONNECTOR
REV B AUG 1980
3-3
I
BUFFERED I
I REFERENCE U50 I
1
(Either internal or
external
I
1I depending upon position of 1
I
jumpers)
1
L
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Theory of Operation-TG 501
Decade Dividers
The decade
dividers operate continuously ; however,
the output
is selected by enabling the appropriate enable
logic gate with a low, via the cam switch
S350 . The =10
dividers are U355,U360,U362, U364, U368,
and U372 . The
NAND enable
logic gates are U330B, U350B-C, U190A-C-
D and U366A-B-C-D . The square-wave pulses
from the
logic gates are differentiated by an RC
circuit using
capacitors C358,C360,C362, C366, C368,
C370 and C372 .
The resistance
for the RC circuit is selected by cam switch
S350
via the 5-2-1 sequence logic gates, depending
upon
the timing position in the 5-2-1 sequence .
The selection
of the resistance for the RC circuit
determines the slope of the falli ngedge of
the marker and
hence controls the marker
brightness . R385, the largest
resistance, is selected in all
positions of the 5-2-1 se-
quence . In the 2 position, a
low from the 5-2-1 sequence
logic gate turns on
Q384 and connects R384 in parallel
.
with R385, reducing the resistance and
the marker
brightness . In the 1 position,
Q380 turns on and R381
parallels R385 to reduce
the resistance and brightness
from that
obtained in the 2 position .
0405
provides a stage of isolation between the decade
dividers and the
low speed marker output amplitude . The
isolation
stage increasesthe impedance seen by the
input
to the low speed marker output
operational amplifier .
Low Speed
MarkerOutput Amplifier
The low speed marker
output amplifier is an
operational amplifier having a
gain of 1 .5 . The amplifier
consists of Q408 and
Q415 with R406 and R410 being the
input resistor
and feedback resistor respectively
.
3- 4
DIAGRAM
3
10 ns, 20 ns, 50 ns MarkerOutput
Amplifier
Q390 and 0400 form
an emitter coupled switch that is
controlled
by U300D, and ECL enable logic gate . U300D
requires a lowfrom the 10 ns, 20 ns, or 50 ns
logic gateto
pass the square-wave .
The square-wave at output pins 15
and 9 of
U300D is differentiated by RC networks C390-
R394
andC400-R400 . The differentiated signal is coupled
through Q400 as long as pin 13 of
U300D remains low . The
output from Q400 is
summed with the output from thelow
speed
marker output amplifier and supplied to the
MARKER OUT connectorJ470 .
Trigger Output
At MARKER
Control settings of 5 s through .1 Ns the
marker available
at the MARKER OUT connector is used
as
a slave trigger . The slave trigger from the low speed
marker output amplifier is coupled
through emitter
followers Q430 and
Q435 and made available at +
TRIGGER
OUT
connectorJ435 .
At Marker Control settings of 50
ns and faster, the
trigger
signal rate available at the + TRIGGER OUT
connector remains .1 has . The .1 /is output is obtained by
enabling logic gates U235D and U330D . Enabling
U330D
allows the output square-wave
from U320 to be differen-
tiated by RC
networkR445-C440, then amplified by Q440
before being coupled to the + TRIGGER OUT connector
via emitter follower 0435 . The rc network determines the
width and amplitude of the trigger signal,
while R439-C439
network in the emitter of
Q440 controls the signal gain .
R445 High
Speed trigger amplitude provides a means of
adjusting the high speed trigger amplitude to match the
low speed trigger amplitude .
REV B AUG 1980
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