Hameg HM303-6 Service Manual Download Page 38

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Subject to change without notice

– Check that trigger starts with ﬁ eld sync. pulses; approx.

2.5 frames should be visible.

–  Change polarity of the video signal.
–  Press SLOPE pushbutton (IN position).
–  Again approx. 2.5 frames should be displayed triggered.
–  Set time base to 20 μs/div for TV line triggering.
–  Now approx. 3 lines should be visible.
–  Change polarity of video signal.
–  Release SLOPE pushbutton to the OUT position.
–  Again 3 lines should be displayed triggered.

Note:

The switch over from frame to line TV triggering is perfor-
med by the time base switch. In time base settings from
0.2 s/div to 0.2 ms/div TV frame triggering is selected. Line
triggering is present from 0.1 ms/div to 0.1 μs/div.

35. Line Trigger

–  Set time base to 5 ms/div.
–  Connect 10:1 probe to CH I input.
–  Place the probe tip close to the oscilloscope mains cable,

so that it can pick up the more or less distorted line/mains
signal.

– Change attenuator CH I setting for a suitable display height

of at least 1 div.

– Press AT/NM and ALT pushbuttons (IN position).

Note:

This combination is marked with a sine symbol indicating
line/mains triggering.

– Check that the Trigger-LED (TR) is ON and the line/mains

signal is stable triggered.

– Disconnect 10:1 probe from CH I input.
– Check that the Trigger-LED (TR) is still ON although no

signal is applied.

– Release AT/NM and ALT pushbuttons (OUT position).
– Check that the Trigger-LED (TR) is OFF.

36. Trigger Filter Check

– Set time base to 1 ms/div.
– Connect a 1 kHz sine wave signal, 40 mV

amplitude,

to input CH I and check for full screen deﬂ ection (80 mm
at 5 mV/div).

– Set input attenuator CH I to 50 mV/div and check for 8 mm

display height.

– Set trigger coupling to AC, DC and LF. The signal must

always trigger.

– Set time base to 50 μs/div.
– Set sine wave generator to 50 kHz and 40 mV

output

amplitude and check for 8mm display height.

– Set trigger coupling to AC and DC. The signal must always

trigger.

– Select LF trigger coupling. Now the signal should not trig-

ger.

37. Component-Tester

– Press Comp. Tester pushbutton (IN position).
– Check that a horizontal trace of approximately 8 div. length

is displayed.

– Connect a short piece of wire between both “COMP. TES-

TER” sockets.

– Check that the trace is displayed in vertical direction with

approximately 6 div. height.

38. Calibrator Output

–  Connect 10:1 probe to CH I input.
–  Check that attenuator CH I is set to 5 mV/div.
–  Insert the probe tip into the 0.2 V

calibrator signal output

socket.

– Check that the 1 kHz / 1 MHz pushbutton is released (OUT

position).

–  Set time base to 0.2 ms/div.
–  Check that approximately 2 signal periods are visible.
–  Press 1 kHz / 1 MHz pushbutton (IN position).
–  Set time base to 0.2 μs/div.
–  Check that once again approximately 2 signal periods are

visible.

Spare-Part List HM303-6

P e r f o r m a n c e C h e c k H M 3 0 3 - 6

Spare Part

Spare Part Number

CRT Board

29-1000-0004

CRT Modul (Tube)

29-1000-0008

FC Board

29-1000-0001

TB Board