Hameg HM 303-4, Service Manual

Subject to change without notice

39

(31) RV2234: X-Magnification x10.

Locate and identify RV2234 (31) on XY-Board.
Press pushbutton X-Mag. x10.
Set time base to 50µs/div.
Set time mark generator to f= 20kHz and connect signal to CH I  input.
Set X-POS control to mechanical center.
Using X-POS control, move the visible time mark to the  first left graticule line.
Adjust RV2234 (31) so that the next time mark coincides with the last (right) graticule line.
Release X-MAG. x10 pushbutton (out!).

(32) R624: XY-Gain

Connect a 1kHz squarewave signal of 25mVpp amplitude (HZ60-2) to input CH II.
Check that the CH II input sensitivity is 5mV/div.
Check that DC input coupling is selected.
Locate and identify R624 (32) on YPA-Board.
Press XY pushbutton.
Set X-POS control that the left dot coincides with the graticule center.
Adjust R624 (32) for a distance of 5 division between left and right dot.

(33) RV3293: Trigger-Symmetry

Locate and identify RV3293 (33) on TB-Board.
Connect a 50kHz sinewave signal of 40mVpp amplitude to input CH I.
Set input coupling CH I to AC.
Check that trigger coupling is in AC position.
Set attenuator switch CH I to 0.1V/div (calibrated position).
Press AT/NORM. pushbutton (in!).
Turn LEVEL control for triggering (center position).
Reduce signal height and correct LEVEL setting for just triggering with a minimum signal height.
Press and release the trigger SLOPE ± pushbutton and adjust RV3293 (33) for stable triggering

in both SLOPE conditions.

(34) R612: DC-Triggering CH I.

Locate and identify R612 (34) on YPA-Board.
Connect a 50kHz sinwave signal to input CH I.
Set generator amplitude to 8cm.
Set time base to 10µs/div.
Press AT/NORM. pushbutton (in!).
Turn LEVEL control to the center position.
Release AC/DC input coupling pushbutton CH I (out!).
Constantly switch between AC and DC trigger coupling and watch the trace start position.
Adjust R612 (34) so that there is no difference regarding the signal start position on the signal

slope between DC and AC trigger coupling.

(35) R603: DC-Triggering CH II.

Locate and identify R603 (35) on YPA-Board.
Connect a 50kHz sinwave signal to input CH II.
Press CH I/II-TRIG I/II pushbutton (in!).
Set generator amplitude to 8cm.
Set time base to 10µs/div.
Press AT/NORM. pushbutton (in!).
Turn LEVEL control to the center position.
Release AC/DC input coupling pushbutton CH II (out!).
Constantly switch between AC and DC trigger coupling and watch the trace start position.
Adjust R603 ( 35) so that there is no difference regarding the signal start position on the signal

slope between DC and AC trigger coupling.