Tektronix 7B85 Instruction Manual page 91

Performance Check and Adjustment_-7885
c. Note the difference in readout from 16 .02 ms . I. Check for a ~ TIME readout of exactly 0.000 ms and
for horizontal alignment of the delayed sweep time markers
within 0.1 div.
d. ADJUST--Set the 'TIME/DIV switch to 1 ms and ad-
just R605 (Scaling) for a 0 TIME readout of 8.000 ms plus
one-half the difference in the readout noted in part c.
EXAMPLE: If the reading in part c was 16 .21 ms, the
difference would be (16.21--~ 16.02) =_= 0.19 ms . Adjust
8605 for a ~ time readout of [8 .000 ms -F 0.5 (0 .19 ms)]
=- 8.095 ms .
e. INTERACTION--Set the O TIME control for a O TIME
readout of 8.000 ms . Repeat parts b, c, and d as necessary.
f. Set the TIME/DIV switch to 5 ms and check for a O
TIME readout between 39 .97 and 40 .07 ms .
g. Set the TIME/DIV switch to 1 ms and rotate the 0
TIME control fully counterclockwise .
h . Set the DELAY TIME control to position the intensi-
fied zones near the second graticule line so that the time
markers in the delayed-sweep display are on the center
graticule line .
NOTE
If it is difficult to set the d TIME control for exactly
2 div (20~s) between delayed-sweep time markers,
note the actual time separation displayed. Then, fol-
low the procedure outlined in part j and adjust R625
so that the d TIME readout corresponds to the actual
time separation displayed between the delayed-sweep
time markers.
EXAMPLE: A 2 .2 div time delay corresponds to a
0.022 ms 0 TIME readout. Adjust R625 for a O time
readout of 0 .021 ms . Then, adjust R625 until the ~ time
readout just changes to 0.022 ms .
j. ADJUST-R625 (DVM Zero) for O time readout of
0.019 ms . Then, adjust R625 until the O TIME readout just
changes to 0.020 ms .
k. Rotate the O TIME control fully counterclockwise .
B10. Adjust DVM Gain (8620)
a. Set the DELAY ~°IME control to start the first intensi-
fied zone on the second time marker and set the ~ TIME
control to start the second intensified zone on the tenth time
marker. Further rotate the D TIME control to horizontally
align the delayed-sweep traces (it may be necessary to
rotate the TRACE SEP control to view the two delayed-
sweep traces).
NOT
If the d TIME control cannot be set to obtain 8 divi-
sions between intensified zones, preset R535 (Second
Pickoff Bias) fully clockwise. Final adjustment of R535
is made in step B12.
b. Check for a ~ TIME readout of 8.000 ms .
c. ADJUST---R620 (DVM Gain) for a 0 TIME readout of
8.000 ms .
i. Advance the ~ TIME control until the first and second
B1 1 . Adjust Delay Start and Second Pickoff Bias
delayed time markers are 2 .0 div (20 ~s) apart (1 horizontal
(R305, R535)
division equals 10 ~s of delayed sweep) .
a. Set the 'i'RACE SEP control fully clockwise into the
switch detent to disable 0 TIME operation.
b. Position both traces horizontally (7885 trace and
companion time-base trace) to start on the first graticule
line.
c. Set the DELAY TIME control for 0.950 ms of delay-
time readout.
d. Check for a delayed-sweep time marker (lower trace)
at graticule center, within 1 .0 div.
e. ADJUST---R305 (Delay Start) to position the delayed
time marker, corresponding to the intensified delaying-
sweep time marker, to graticule center.
f. Rotate the TRACE SEP control counterclockwise, just
out of switch detent, to enable the ~ TIME mode . Set the
DELAY TIME control fully counterclockwise and the d TIME
control fully clockwise.
5- 1 4
REV AUG 1981