Tektronix 1740A Series, User Manual

Page: 178 / 368

Maintenance
1740A/1750A/1760 – Series Service Manual
6–11
d. Using the digital multimeter, measure the voltage at U6, pin 3. It should
be approximately 5 Vdc. Short the base to the emitter of Q15. Pin 3
should now measure 0 V.
WARNING. Dangerous potentials exist on this circuit board. Extreme care should
be exercised in troubleshooting these circuits.
1. Preliminary Checks
a. Table 6–6 lists the High Volts Supply fault symptoms and procedures.
Table 6–6: High Volts Supply Fault Symptoms
Symptom Procedure
Unable to focus CRT using the
front-panel control Focus Amplifier Check
Unable to adjust CRT intensity using
the front-panel control Z-Axis Amplifier Check
Grid Drive Check
No CRT display High Voltage Oscillator Check
CRT Voltage Check
b. Load the Low Volts Supply with the instrument.
2. Focus Amplifier Check
a. Using the digital multimeter, measure the voltage between TP1 and the
collector of Q2.
b. It should vary from 0 to –300 Vdc when the front-panel FOCUS control
is rotated.
3. Z-Axis Amplifier Check
a. Using the digital multimeter, measure the voltage between TP1 and the
collector of Q6.
b. Short together the base and emitter of Q3. The collector of Q6 should be
near 0 V.
c. Short together the base and emitter of Q4. The collector of Q6 should be
near 0 V.
High Volts Supply
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com