Tektronix 2445, Instruction Manual

Page: 130 / 351

Adjustment Procedure— 2445 Service
Table 5-3
Horizontal Timing
Step No. Time-Marker Period
Markers Over
8 Divisions
17
1
n$
8
18 1
juS
24
19
2
fis
8
20
2
fis
24
21 10 MS 8
22 50
ms
8
23 50
ms
24
24 500 ns 8
25 500 ns
24
26 100 ns 8
27 20 ns 8
CD
00
C
M
skipped
29 1 ms 8
aFirm ware in the 2445 is shared with a similiar instrument, the
2465, which requires step 28. The 2445 skips step 28.
N O T E
If the rem ainder o f the A djustm ent Procedure w ill n o t
b e p erform ed (in totality), readjustm ent o f H orizo ntal
R eado u t J itte r (R 8 0 5 ) m ay be necessary if the X I
G ain (R 8 6 0 ) o r the X I 0 Gain (R 8 5 0 ) w as changed.
S ee subsection 2 on p ag e 5 -1 7 for th at procedure.
dd. Disconnect the test setup.
CAL 02— VERTICAL
2. Check/Adjust Vertical Preamp Gain, Gain
(R638), and Vertical Centering (R639).
N O T E
if the previous step (C A L 0 1 ) w as n o t perform ed, the
adjustm ents in this subsection should only be p er­
form ed if those constants th a t would have been s e t in
CAL 01 are know n to be correct.
a. Set the front-panel INTENSITY control at midrange.
b. Scroll to CAL 02,
c. Press up and release the TRIGGER COUPLING
switch. The instrument will automatically increment through
steps 100 to 111.
d. CHECK— Readout indicates CH 1 VAR, CH2 POS,
(step) 111, 500 mV, and BWL.
N O T E
The read o ut p rom pts the o p erato r b y show ing the
controls to b e m oved (upper le ft co m er an d upper
center), the au to cal step num ber (upper rig h t corner),
the am plitude o f signal to be applied to eith er the C H 1
o r C H 2 connectors (low er le ft corner), an d an y o th er
scope function th a t is enabled. A n exam ple (from step
d above) is:
CHI VAR CH2 POS 111
500 mV BWL
e. Connect a 0.5 V, standard-amplitude signal from the
Calibration Generator to the CH 1 OR X input connector via
a 50 S2 BNC cable.
f. Use the CH 2 POSITION control to vertically position
the trace to within 1 division of the center graticule line.
g. ADJUST—CH 1 POSITION and VOLTS/DIV VAR
controls to obtain a 10-division horizontal signal. Press up
and release the TRIGGER COUPLING switch.
h. CHECK— Readout indicates MOVE SW, CENTER
CHI POS, (step) 112,100 mV, and BWL; then press up and
release the TRIGGER COUPLING switch.
i. ADJUST— CH 1 POSITION control carefully until the
CH 1 input coupling “1 Mfi DC” indicator remains illuminat­
ed, then press up and release the TRIGGER COUPLING
switch.
N O T E
In the follow ing steps, if the “L IM IT ” m essage ap­
pears, it probably indicates th at the TR IG G E R C O U ­
P LIN G (step) sw itch w as m oved before the required
signal was applied. Press dow n and release the TR IG ­
G ER C O U P L IN G sw itch, verify th at the correct signal
is applied, then press up an d release the TR IG G ER
C O U P LIN G switch.
j. CHECK— First step number listed in Table 5-4
appears in the readout.