Front End (Fv) - Philips VR120 Service Manual

GB 92 8.
Notes:
With varying frame amplitudes, the setting is made for the
greatest amplitude.
A: AC, 50mV/Div, 20us/Div
8.4

Front End (FV)

Service tasks after replacement of IC 7705, coil L5702 and
TUMOD:
8.4.1 AFC Adjustment:
Purpose:
Correct adjustment of demodulator AFC - circuit
Symptom, if incorrectly set:
Bad or disturbed TV channel reception.
PAL - AFC adjustment [5702]:
SECAM band 1 - AFC adjustment [3730]: (SECAM L / L'
only)
Before commencing adjustment:
– Switch to a band 1 SECAM L' preset.
– Is the system switch, in the menu 'MANUAL
SEARCHING', not possible, press the right cursor key of
the remote in the 'CHANNEL NUMBER' line for a short
moment.
– A fine-tuning will be done and the system will switch to
the 'AUTO' function.
VR120 Electrical alignments
REC
A
8.4.2 HF - AGC adjustment [3707]:
Service tasks after replacement of ICs 7705, or TUMOD:
Purpose:
Set amplifier control.
Symptom, if incorrectly set:
Picture jitter if input level is too low and picture distortion if
input level is too high.
8.4.3 Attenuating the 40.4 MHz [5704]: (SECAM only)
Service tasks after replacement of coil 5704:
Purpose:
To attenuate the band I carrier rests.
Symptom, if incorrectly set:
Bad picture quality when the filter attenuates the picture
carrier (38.9MHz).
If the adjustment is correct the signal at pin 1 of SFW [1704]
must be smaller than the input signal amplitude by at least 5
dB.