Tektronix 7834

The 7834 crt has a special high-speed target, known as the
fast target, located just behind the storage target . The fast
target has an extremely high writing speed but retains
images for only a fraction of a second . For this reason
images stored on the fast target are quickly and auto-
matically transferred to the storage target ; this operation is
called transfer storage . Transfer storage can be used with
the storage target operating
in either bistable or variable
persistence mode, resulting in
the FAST BISTABLE and
FAST VAR PERSIST modes .
In either of the FAST modes the writing speed is adjusted
by the STORAGE LEVEL control, as well as the crt
INTENSITY controls . Maximum
stored writing speed in
both FAST storage modes is attained by setting
the
STORAGE LEVEL and INTENSITY controls fully
clockwise
.
In all storage modes,
an
erase
cycle removes any previous
display from the storage target . This prepares the
storage
and
fast targets (in the FAST storage modes) to receive the
next waveform . Erase cycles are initiated by pressing the
ERASE
push button, grounding the rear panel REMOTE
ERASE INPUT, or by
rotating the AUTO ERASE control
out of the OFF (detent)
position . The AUTO ERASE
control can be set to erase the storage display in 1- to 10-
second intervals .
Two modes of operation for the
AUTO ERASE function
are available, either Erase After Sweep
or Periodic Erase
(refer selection of either mode
to qualified service personnel
In the VAR PERSIST mode,
points on the storage target
can vary in luminance between
totally dark and very
bright . In this mode, writing speed
is
greater than
in the
BISTABLE mode, but the stored display is essentially
unstable,
or continuously fading away . The rate of fading
is adjusted by the PERSISTENCE control . the VAR
PERSIST storage mode is particularly useful for viewing
high-speed
repetitive signals with low repetition rates . The
PERSISTENCE control can be adjusted in
conjunction
with the STORAGE LEVEL and INTENSITY
controls,
to produce a steady, bright trace . Writing speed
is
varied
in this mode by the STORAGE LEVEL control as well
as the crt INTENSITY controls . Maximum stored writing
speed is achieved by setting the INTENSITY controls and
the STORAGE LEVEL control fully clockwise .
Electric-shock hazard . Only qualified
service
personnel should internally modify
the oper-
ation of the instrument .
Operating Instructions-7834
only) . The
two modes differ in the following ways :
The
Erase After Sweep mode requires that the displayed time-
base unit complete a sweep in order to initiate the delay
interval
prior to the
erasure ;
the Periodic Erase mode repet-
itively erases independent
of
the
displayed
time-base
operation .
Both time-base units and the readout system are inhibited
during the erase cycle . Also during each erase cycle, the
displayed time-base unit is reset if it is in single-sweep
mode . (The other time base will also be reset at this
time if it is also in single-sweep mode .) In the BISTABLE
and
VAR
PERSIST
storage modes, the erase cycle takes
approximately 0 .9 second ; in the FAST BISTABLE and
FAST VAR PERSIST - modes, the erase cycle takes
approximately 1 .4 seconds . The additional time is required
for preparing the fast target .
In all storage modes the time-base
unit(s) is free to
run
immediately following an erase
cycle
.
However, in
FAST
BISTABLE or FAST VARIABLE PERSISTENCE
storage
modes, the time-base unit(s) is locked
out immediately
after the first sweep occurs,
so that transfer can occur . (in
the ALT
or CHOP horizontal modes, both time-base units
are allowed to run once before
transfer occurs .) If the time-
base unit(s) is set for single-sweep
operation, it remains
locked out indefinitely after
transfer occurs . The operator
can initiate a cycle, however,
called
the
multi-trace cycle,
which causes another
trace to be stored without erasing the
initial
display . This is accomplished by pressing the single-
sweep-reset
button on the time-base unit(s), or by ground-
ing
the REMOTE RESET INPUT on the 7834 rear panel .
When this is
done
the
storage system initiates a cycle,
lasting approximately
600 milliseconds, which prepares the
fast target to store another
display and sends an additional
single-sweep-reset command
to
the
time-base unit(s) . After
the multi-trace cycle, the time-base unit(s) can again sweep
once, after which it is again locked out and the transfer
function
occurs .
When the time-base unit(s)
is operated
in
other than a single-
sweep mode, the multi-trace cycle is
controlled by
the
MULTI TRACE DLY control . If the MULTI TRACE DLY
control is set to its detent position, operation is
as
previously
described for the single-sweep mode . If the
MULTI TRACE
DLY control is out of the detent
position, the multi-trace
cycle is triggered automatically following the transfer
cycle .
The length of the cycle can be varied by
the MULTI
TRACE DLY control over a range from
approximately 600
milliseconds to more than 4 seconds .
SAVE MODE . The SAVE mode can be entered
from any
storage mode by pressing the SAVE
button or by grounding
the rear-panel REMOTE SAVE INPUT . The
indicator next
to the SAVE push button switch illuminates
when the
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