Tektronix 7T11A, Instruction Manual

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Maintenance—7T11A
11. Check Trig Level Zero. Set the STABILITY control
for free running within a narrow band. The Schmitt Trigger
circuit should still free run within this narrow band when +
or — slope is selected.
h. Strobe Drivers—To get an output, return the collector
of A2Q342 to ground through a resistor (100 Ω to 1 k).
i. Stop Drive to (—) Slope Driver (input of A2Q252).
12. Check the TRIG LEVEL indicator dot position to be
2 o’clock when Trig Level Zero is properly adjusted. For this
check use 50 Ω, ext trig input, zero signal.
j. Time to Height Converter.
13. Check Arming Bias and Output Bias adjustments
A3R145 and A3R155 are be set for triggered operation. Use
the Pulse Generator recommended for use in Section 5.
k. Horizontal Amplifier.
I. Horizontal Memory Gate Driver.
14. Check the Holdoff Multivibrator; it should now run.
Check for operation in all equivalent-time (sequential) posi­
tion ranges.
m. Horizontal Memory—Memory Gate Bal adjustment
A2R550 may now be set.
15. Check for operation of the following circuits with
the Holdoff Multivibrator running. Set TIME POSITION
RANGE to 5 µS and refer to waveforms shown on the sche­
matics in Section 8 of this manual.
n. Output Amplifiers.
o. Dot Position Memory—Once the output amplifiers
have been checked, reconnect the 510 Ω resistor.
a. Pulse Out Driver—When this circuit is functioning, the
test scope can be triggered by this pulse.
b. Trigger Coupling Amplifiers.
c. Start Multivibrator.
d. Slewing Ramp—It may be necessary to unplug one
end of 510 Ω resistor A1R586. Set TIME/DIV to .1 µs and
TIME POSITION to midrange.
e. Time Position Amplifier (A1U572D).
16. Check Time To Height Converter output. Switch
sampling mode from Sequential to Random. Set TIME PO­
SITION RANGE to 5 µs or 50 µs. Set the TIME POSITION
control full counterclockwise. Use the test oscilloscope and
monitor the Time To Height Converter output. The plateau
between the start multivibrator firing and the trigger input
should be flat, with no + or — slope.
If the unit does not work properly in Random mode,
check the Ratemeter and the Ratemeter Correction Memory
for correct operation.
f. Slow Ramp Generator.
g. Slewing Ramp Comparator—the collector of A2Q328
should change from -15 V to about +3 volts in 2 ns.
17. Check for operation in Real Time sampling mode.
If not functional in the .5 µs TIME POSITION RANGE, check
the Real Time Multivibrator and feedback reset path
through A2Q554 to the Holdoff Multivibrator.
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