Zanussi 22ZT907, Service Manual

Page: 23 / 64

PCB BS
Denomination
Luminance-chrominance and video
output amplifier.
Adjustment procedure
Preliminary operations
Check that the p.c.b. is correctly supplied:
25OmV on contact
F12; DC on contact G5; DC contact
12 Vpp on contact F14; Vpp on contact G2; 11 Vpp on contact
Brightness and contrast controls to maximum (adjustment on remote
control when provided).
Colour saturation to minimum.
Grey scale signal in antenna. Correct tuning.
Adjust black-level potentiometers to max. (clockwise)
Adjust gain potentiometers,
to max. (anticlockwise).
Oscilloscope with attenuated probe on contact F2.
Check that the
2.65 Vpp.
Operations
Oscilloscope's
Adjust
to
Oscilloscope's
Adjust
to
Oscilloscope's
Adjust
to
probe on red output (H4).
set the reference level (see figure 4) to 170V DC.
probe on green output (H2).
set the reference level to 170V DC.
probe on blue output
position the reference level to 170V DC.
Colour bar signal in antenna. Correct tuning. Saturation to max.
Oscilloscope's probe on TP102. Apply a 1 V DC voltage to TP103.
Adjust
for max. amplitude of signal displayed.
Suppress voltage applied to TP103.
Plug in jumper S103. Disconnect
Adjust Cl23 for minumum bar horizontal drift.
Disconnect S103. Reconnect
Test 3 signal (delay) in antenna.
Oscilloscope's probe on red output (H4).
Adjust
and, if necessary, so as to perfectly align the
bottom portion of the signal displayed.
Test 2 signal (phase) in antenna.
Adjust
for best superimposition of the two wave shapes displayed.
signal present on this point has a total width of