HEIDENHAIN TNC 306 Service Manual - Manual (Page 51)

SERVICE MANUAL TNC 306/360
Page 44
HEIDENHAIN Service
If the VDU remains dark after the test button was pressed, the VDU is defective and must
be exchanged.
If however, the highlighted field appears, the processor board of the LOGIC UNIT is
probably defective.
In addition, the control signals for the VISUAL DISPLAY UNIT can be checked with an
oscilloscope.
Procedure:
Connect the measuring adaptor between the VDU and connector X9 of the LE.
Measure the signals at the corresponding pins and compare the results to the following
diagrams.
2V/DIV H-SYNC PIN 10
20 µs/DIV
2V/DIV V-SYNC PIN 9
5 ms/DIV
2V/DIV VIDEO PIN 13
5 ms/DIV
Note:
With the VIDEO diagram (pin 13) a deviation in the time axis can occur, depending on the
image being displayed.
Moreover, the amplitude (video) doubles, if:
- the VDU is disconnected
or
- the external test button is pressed.