Adjust External Horizontal Amplifier; Balance (R 186); Variable Control I S Rotated; Adjust External Input Gain (R25) - Tektronix 7B70 Time Base Instruction Manual

Performance Check/Calibration-7B70 (SN I3205000 and Up)
6. Adjust DC Level Center (R 121
)
0
a. Set the TRIGGERING MODE t o P-P AUTO, DIS-
PLAY MODE t o TIME BASE and apply a one volt signal
a. Set the LEVELISLOPE control near 9:00 and adjust from the standard amplitude calibrator to the EXT TRIG
for a stable display. I N connector. Set the 7870 TIMEIDIV t o .2 ms.
b. ADJUST-Change the TRIGGERING COUPLING to
DC and adjust R121 for a stable display. Return the TRIG-
GERING COUPLING to AC.
7. Check SINGLE SWEEP MODE
a. Adjust the LEVELISLOPE control for a stable dis-
play and change the TRIGGERING MODE t o SINGLE
SWEEP.
b. CHECK-Remove the signal from the 7A16A. Press
the RESET button and check that the READY light is lit.
Reconnect the signal to the 7A16A and check that the
sweep runs one time. (Increase the B lntensity as necessary
to view the trace.) A t the end of the sweep, the ready light
should go out. Reduce the B Intensity t o its level before
step 7.
c. Disconnect the signal from the Type 191
8. Adjust External Horizontal Ampli-
0
f ier Balance (R 186)
a. Set the COUPLING to DC and the DISPLAY MODE
t o AMPLIFIER. Set the SOURCE switch so that all buttons
are out (this may be accomplished by pressing lightly on
one of the buttons until all the buttons are cancelled).
b. ADJUST-R186 to bring the dot on to the display
area. While rotating the AMPLIFIER VARIABLE control,
adjust R186 for minimum movement of the dot as the
VARIABLE control i s rotated throughout i t s range.
9. Adjust External Input Amplifier
0
Balance (R37)
a. Set the SOURCE t o EXT.
b. ADJUST-While rotating the AMPLIFIER VARI-
ABLE control throughout
i t s
range, adjust R37 for mini-
mum movement of the dot.
10. Adjust External Input Gain (R25)
0
NOTE
Step 10 requires two 7A 16A
amplifiers or a dual
trace amplifier such as the
7A 12.
b. Set the Oscilloscope Vertical Mode to Add. Set both
7A16A VoltsIDiv to
50
millivolts. Set the Polarity switch
of the 7A16A in the right vertical compartment t o Invert.
Connect a 1X probe from the left vertical plug-in to pin F
on the External lnput board and a 1 X probe from the right
vertical plug-in to pin H on the External lnput board. See
Fig. 5-2 for location of pins.
Fig. 5-2. Location of pins for Calibration Step 10.
c. ADJUST-R25 for a four division display on the
CRT.
11. Check Horizontal Amplifier Gain
a. Reset the DISPLAY MODE to AMPLIFIER and turn
the amplifier VARIABLE control fully clockwise. Apply a
0.1 volt signal from the standard amplitude calibrator to
the EXT VOLTS I N connector.
b. CHECK-Display amplitude should be between 3.2
divisions and 4.8 divisions.
c. Reset the SOURCE switch to EXT + I 0 and the
standard amplitude calibrator to 1 volt.
d. CHECK-Display amplitude should be between 3.2
divisions and 4.8 divisions.
Scans by ArtekMedia O 2006