Hameg HM 303-4, Service Manual

Subject to change without notice

41

(36) RV2301 (A), 4322 (B): Component Tester Y-Position and Tilt.

Release all pushbuttons (out!).
Press COMPONENT TESTER pushbutton (in!).
Locate and identify RV2301 (36A) on XY-Board.
Adjust RV2301 (36A) to shift the approx. 8 div. horizontal component tester trace to the

horizontal center of the CRT graticule.

Locate and identify RV4322 (36B) on CC-Board.
Set up the instrument on a table in normal operating conditions to avoid misadjustment due

to the influence of the earth magnetic field.

Adjust RV4322 (36B) in such a way that the trace is parallel to the horizontal graticule center line

and not tilt. This adjustment

(37) VR8940: Calibrator Output.

Locate and identify VR8940 (37) on CC-Board.
Connect a digital multimeter to the 0.2Vpp calibrator output.
Set up the digital multimeter for DC measurement in a suited sensitivity setting.
Locate and identify IC8903 on CC-Board.
Connect pin 1 and pin 14 of IC8903 galvanically together.
Adjust VR8940 (37) for exactly 0.2V DC.
Check 2V calibrator output.
Remove the connection between pin 1 and pin 14 of IC8903.

Connect a 10:1 probe to the 0.2Vpp calibrator output and connect it to the CH I input of the scope.
Release all pushbuttons (out!).
Select CH I DC input coupling.
Set attenuator CH I to 5mV/div (calibrated detent).
Set time base to 0.2ms/div.
Now approximately 2 signal periods should be visible on the screen.
Press 1kHz/1MHz pushbutton (in!).
Set time base to 0.5µs position.
Check 1MHz calbrator signal.

Please note:

Neither the calibrator frequency nor the pulse duty factor are specified.

(38) Trigger Filter Check.

Set time base to 1ms/div.
Connect a 1kHz sinewave signal of 40mVpp amplitude to input  CH I and check for full

screen deflection.

Set input attenuator CH I to 50mV/div and check for 8mm  display height.
Select trigger coupling from AC to DC and LF. The signal  must always trigger .
Set sinewave generator to 50kHz and 40mV output amplitude  and  check for 8mm display height.
Select trigger coupling from AC to DC. The signal  must always trigger.
Select LF trigger coupling. Now the signal should not  trigger.

(39) Triggerbandwidth Check.

Set time base to 0.05µs/div, time base variable to CAL  position.
Set input coupling switch CH I to DC.
Set trigger coupling to AC.
Release AUTO/NORM pushbutton (out!).
Set input attenuator CH I to 5mV/div.
Connect a 100MHz sinewave signal to input CH I.
Adjust generator output for 5mm display height.
The signal must be triggered.

(40) External Trigger Check.

Set time base to 20µs/div.
Set input attenuator CH I to 0.1V/div.
Connect a 50 kHz sinewave signal via a 50-Ohm through terminator with an amplitude of

280mVpp (100mVrms) to input CH I and check for 2.8div display height.

Set LEVEL to midrange position.
Check that the Trigger-LED is ON.
Press EXT. pushbutton. The Trigger-LED (TR) should now be OFF.