Tektronix 511A, Instruction Manual

Page: 11 / 74

SECTION II
OPERATING INSTRUCTIONS
The Type 511-A may be operated in any normal in­
door location, or in the open if protected from moisture.
If the instrument has been exposed to dampness, it
should be left in a warm room until thoroughly dry, be­
fore being placed in operation.
To prevent excessive interior temperatures, it is im­
portant to allow adequate ventilation for the oscillo­
scope. Several inches clearance should be provided at
the sides, back and top of the case.
If the Type 511-A is used continuously for the same
application, and only one setting of the controls is re ­
quired, it is advisable to periodically check the instru­
ment at all control settings to be sure it is in normal
operating condition. For example, if only direct connec ­
tion to the vertical deflection plates of the CRT is used,
a defect in the
video amplifier might
not become evi ­
dent. Operation of the controls also helps to prevent
accumulation of dirt and tarnish on their contacts.
Although the components are well supported and the
adjustments very stable in setting to allow for portable
operation, the Type 511-A should not be subjected to
excessive vibration or rough handling.
To place the Type 51 1-A in operation for the first time
the following procedure is suggested.
1. Connect to a source of 50-60 cycle, 105-125V power.
2. Set controls as indicated below.
3. Turn POWER switch to ON and wait about 30
seconds.
INPUT CHAN. SEL............. ..................... 1 STAGE
INPUT ATTENUATOR ... ................................ X1
VERT. AMPL. ATTEN ....... ...................Clockwise
SIGNAL CALIBRATE .... ................................ X 1
VERT. POSITION.. ........ .............
Index vertical
CAL. VOLTAGE .............. ....................................
0
ASTIGMATISM .................. ............ Index vertical
INTENSITY ...................... .... Counterclockwise
FOCUS ................................ ..............Index vertical
HOR. POSITION ..................................... Clockwise
SWEEP MAGNIFIER POSITION ................... OUT
SWEEP
SPEED
MULT....
..................................... 5
SWEEP RANGE................ ..........................
10,000
SWEEP STABILITY .......... ....
Counterclockwise
TRIGGER AMPL...............
... .Counterclockwise
TRIGGER SEL ................... ........................... +INT.
4. Advance INTENSITY control until a spot is seen.
5. Adjust VERT. POSITION, HOR. POSITION, ASTIG­
MATISM and FOCUS until a sharply focussed spot is
obtained at the left center of the screen.
CAUTION — DO NOT ALLOW THIS SPOT
TO BE EXCESSIVELY BRIGHT OR RE­
MAIN FOR LONG IN ONE POSITION.
6. Advance the SWEEP STABILITY control until a
sweep appears, then turn it back just under
this
point.
7. Set the CAL. VOLTAGE control to 10. A vertical
line about 1 ½ inches high should appear.
8. Advance the TRIGGER AMPL. control until a
stable image of a sine wave appears.
The oscilloscope is now observing the 50-60 cycle
power line waveshape. To observe other waveshapes
connect them to the SIGNAL INPUT binding post, turn
the SIGNAL CALIBRATE switch to SIGNAL, select the
appropriate sweep speed, etc.
SWEEP CIRCUIT ADJUSTMENTS
The sweep circuit of the Type 511 A is different from
the gas tube type usually employed in portable oscillo ­
scopes. It is much more flexible and capable of syn­
chronizing with much higher frequencies than conven ­
tional sweep circuits. Fundamental frequencies of 10
mc
and
higher can be
easily
observed. By
one
simple
adjustment the sweep will run recurrently or triggered
as desired.
In a recurrent or sawtooth sweep as generated by a
gas tube or similar device the synchronization takes
place at the end of the sweep. The sync impulse causes
the beam to return to the left side of the tube where it
immediately starts another sweep. Thus the sweep time
must be a multiple of the signal period, or expressed
another
way, the
sweep frequency
an
integral fraction
of the signal frequency.
In a triggered sweep circuit each sweep is started in ­
dependently of the preceeding sweep by a trigger or
synchronizing impulse. When no trigger is being re ­
ceived, the beam remains at the left side of the trace.
When the trigger arrives, the beam goes linearity to the
right for a time in this case determined by the multi ­
vibrator pulse length. At the end of its sweep it returns
to the left side again to await another trigger. It is this
variable waiting period which makes the synchroniza­
tion so easy since the sweep time is now independent
of the signal period. The triggered sweep makes it pos ­
sible to view pulses such as used in radar and tele ­
vision where the length of the pulse is very short com­
pared to the space between pulses. This requires a fast
sweep with a long waiting period. Waiting periods of
2000 times the sweep length are frequently used.
ADJUSTMENT OF SWEEP STABILITY
The SWEEP STABILITY control varies the multivibra ­
tor bias and therefore detemines whether the sweep
will oscillate recurrently or wait for a trigger impulse.
Correct functioning for triggered operation is therefore
obtained when it is set just under the point where oscil ­
lation takes place. The procedure is to remove the
trigger source, turn the TRIGGER AMPL. control counter ­
clockwise, and advance the SWEEP STABILITY knob
until a sweep appears and then decrease it until it just
disappears.
SECTION 2, PAGE 1
TYPE 511-A, 511-AD