Tektronix 1705A instruction manual High Voltage Oscillator Check, CRT Voltage Check

Maintenance

Connect the oscilloscope probe to the anode of CR5 and the probe ground to TP1. The signal should be a clipped sine wave of +75 to +200 V p-p.

High Voltage Oscillator Check

Connect the oscilloscope probe to T1 pin 3 (Q6 collector) and the probe ground to TP1. Power up the supply. The signal should be a +60 V p-p, 22 kHz sine wave.

Check the following voltages using the digital multimeter:

Table 6- 6: High Voltage Oscillator Test Points

Circuit Location	Voltage
T1, pin 4	Approximately +40 V.
T1, pin 13	Less than +2 V.
U2, pin 2	Approximately +4.8 V.
U2, pin 6	+4 to +11 V.
CR9, cathode	Approximately +100 V.

CRT Voltage Check

NOTE. This check requires a high voltage probe having an input resistance of 1 GΩ or more.

Connect the high voltage probe ground to TP1.

Load the Low Volts Supply with the instrument, or with a 20Ω, 2 watt resistor loading the 5 V supply.

Power up the Power Supply.

Use the high voltage probe to measure the voltage at the anode of CR4. It should be approximately -2530 V.

Measure the voltage at the anode end of CR3. It should be 50-150 V more negative than the reading from the anode of CR4.

1705A Spectrum Monitor 6- 17