Tektronix 3A9 Instruction Manual page 9

SECTION 2
OPERATING INSTRUCTIONS
Type 3A9
Change information, if any, affecting this section will be found at the
rear of the manual.
FRONT PANEL
(See Fig. 2-1)
This section opens with a brief functional description of
the front-panel controls, INPUT OVERDRIVE light, input
connectors, securing latch and SIGNAL OUTPUT connector.
Following the front panel description is a familiarization
procedure and finally a general discussion of the operation
INPUT OVERDRIVE Input overdrive indicator lamp. Indi-
cates excessive differential drive to the
input amplifier stage. An input of ap-
proximately 90% of the differential dy-
namic range between input connectors
causes an overdrive indication.
Volts per displayed division-current per
displayed division (charceal-colored
knob). Nineteen position switch used to
select the calibrated deflection factors.
VARIABLE Variable volts-current per division (red
knob}. Provides continuously variable
uncalibrated attenuation between the
calibrated deflection factors and ex-
tends the attenuation range to at least
25V/DIV. Control is calibrated in the
CAL position.
UNCAL Indicates VARIABLE control is not in
GAIN Screwdriver-adjust control to set the
amplifier gain (CRT display scale factor}
to agree with the VOLTS/DIV switch
indication. Adjusted for proper deflec-
tion when the VOLTS/DIV is set to the
1 mV position.
POSITION The control which vertically positions
the trace or display.
Nine-position switch which selects the
approximate upper frequency —3dB
point. The switch positions are: .1, .3,
1, 3, 10 and 30 kHz; and .1, .3 and 1
LOWER —3 dB
FREQUENCY
Eight-position switch which selects DC
OFFSET, DC or one of six low-frequen-
cy —3dB points: .1, 1, 10Hz and .1,
1 and 10 kHz.
Signal input connector. Positive input
produces upward deflection {see Fig.
+ INPUT
— INPUT
CURRENT PROBE
L F COMP
CURRENT/VOLTS
(—INPUT)
DC BAL
(DC mode only)
(DC OFFSET mode
SIGNAL OUTPUT
SECURING LATCH
Signal input connector. Positive input
produces downward deflection (see Fig.
Current probe input. For use with 125-
turn current probes (Tektronix P6016,
Compensates for low frequency losses
of the current probe.
Two-position switch which selects Cur-
Three-position switch to select input
coupling. AC and DC positions deter-
mine the method of coupling the signal
to the preamp. The GND position dis-
connects the signal from the preamp
and grounds the preamp input. The
GND position also permits the coupling
capacitor to charge before switching to
AC to prevent overdriving the preamp.
Same function as the +INPUT coupling
Front-panel control for DC balancing
the amplifier input stage. With no sig-
nal applied to the input connectors, the
control is adjusted for no trace shift as
the VOLTS/DIV switch is rotated from
the 10 mV position to the 10 2V posi-
COARSE and FINE controls to provide
internal offset bias while maintaining
the differential capability. Available
range of the offset bias depends upon
the setting of the VOLTS/DIV switch,
and is indicated by color-coded bands
around the VOLTS/DIV switch.
Signal output connector. Provides a
DC coupled output signal at approxi-
mately 1 volt per displayed division
(depending on CRT deflection factor}.
Gray knob near the bottom center of
the front panel to lock the plug-in unit
into the plug-in compartment.
FIRST TIME OPERATION
Preparation
Steps 1 through 5 in the following procedure are intended
to help you get the trace on the screen quickly and pre-
2-1