Philips VR2022/00 Service Seite 98

5-16
GB) U82(LLR) Adjustments
Note:
Measurements and adjustments to this module are possible
only with the aid of an extender board, code number
4822 263 70118
© 3046 (fo = 3,3 MHz)
— Connect frequency counter to 22U82.
— Disconnect 2028,
— Adjust 3046 for a counter reading of 3,3 MHz
(£50 kHz).
— When the FM sweep and white clipper need also be
adjusted, note the DC level at 10-7052 (approx. 3,8 V)
'on the oscilloscope (DC position).
*@ 3042, 3044 (FM sweep, white clipper}
— First of all set fg (3046) to 3,3 MHz.
— Disconnect the slider of 3042.
— Connect power supply unit (PSU) to 10-7052 (set
to approx. 4 V).
— Disconnect 2028.
— Connect frequency counter to 22U82.
— Adjust the voltage from the PSU for a reading of
4,75 MHz (+ 50 kHz) on the frequency counter.
— Note the DC level at 10-7052 (approx. 4,7 V) on the
oscilloscope (DC position).
— Remove the PSU and eliminate the interruptions at
2028 and slider of 3042.
— Tune the VCR to a white pattern from a test pattern
generator.
— By means of 3042 adjust the white level to the DC
level noted last (approx. 4,7 V) on the oscilloscope.
— Subsequently, adjust 3044 so that the amplitude of
the overshoot (C) is equal to 80 % of the difference
in voltage between black and white (D). Refer to
Fig. 5-1.
© 3038 (nonlinear pre-emphasis)
— Disconnect 2028.
— Inject a 1 MHz - 2,2 Vpp sine-wave generator signal,
through 100 nF, to 2-7052 (= 0 dB).
— Connect AC millivoltmeter to 7-7052.
— Select RECORD made.
— Adjust 3038 for + 9,5 dB (6 Vpp) reading.
— Check:
at300kHz +7 dB+1dB(5 Vpp+0,5V).
at 2MHz +9,5dB + 1dB (6 Vpp + 0,5 V).
© 3047 (symmetry adjustment FM modulator)
Method 1
— Set the VCR to the recording mode, no signal being
applied.
— Connect an oscilioscope to 22U82.
— Adjust 3047 so that the positive and the negative
halfcycles are symmetrical.
Method 2
— Set the VCR to the recording mode, no signal being
applied.
— Connect both the Yq and the Yg input of an
oscilloscope to 22U82.
— Add the two channels and invert one channel.
— An oscillogram as shown in Fig. 5.2. is now obtained.
— Adjust 3047 so that the distances B-A and A-C are
equal.
CS 76 616
© 3050 (adjustment of luminance write current)
— Connect an oscilloscope to 22U82.
— Set the VCR to the recording mode, no signal being
applied.
— Adjust the signal amplitude on 22U82 to 6 Vp.p
with 3050.
® 3032 (modulation depth)
— Tune the VCR to the white pattern from a test pattern
generator.
— Connect the oscilloscope, not earthed to the mains.
— Connect the oscilloscope to 4U82 (video).
— Connect the earthing lead of the probe to 3U82
{balance voltage).
— Connect 3U82 to earth via an electrolytic capacitor
(£7 uF).
— Set the oscilloscope to position 0' and move the
horizontal line to the top of the screen with the
"position" control.
— Mark the position of the horizontal line.
— Now set the oscilloscope to "DC.
— Adjust 3032 so that the white level in the video signal
is situated 150 mV below the previously marked level
of the horizontal line.
© 5001, 5002, 5011, 5012
The above coils are provided with adjustable cores. During
manufacture of these coils they have accurately been
adjusted to a specific self-inductance (+ 2 %) with
these cores.
The adjustment of these cores should never be changec.
¢ C=08D
4.75MHz
D |A=Ca1Vpp
3.3MHz
Ra 24 416 A16
B A c
19 379 A13
Fig. 5.2
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6002 6001, 5007, 7003.7005+ 7007, 70017002 S001 5006. 7023 7012. 7013 70th so
U82 LLR
@D U82 (LLR) _ Instellingen
Opmerking:
Metingen en instellingen op deze module kunnen alleen
worden uitgevoerd met behulp van een verlengprint.
Codenummer verlengprint 4822 263 70118.
© 3046 (fo frequentie 3,3 MHz)
— Frequentieteller aanstuiten op 22U82.
— 2028 onderbreken.
— 3046 afregelen op 3,3 MHz {+ 50 kHz).
- Indien de FM-zwaai en witbegrenzer ook afgeregeld
worden, het DC niveau van 10-7052 (+ 3,8 V) aan-
tekenen op het oscilloscoopscherm (stand DC).
© 3042, 3044 (FM-zwaai, witbegrenzer)
— Regel eerst de fo frequentie (3046) af op 3,3 MHz.
— Loper van 3042 onderbreken.
~ PSA aansluiten op 10-7052 (instellen op + 4 V).
— 2028 onderbreken.
— Frequentieteller aansluiten op 22U82.
— PSA spanning zodanig instellen dat de frequentieteller
4,75 MHz (+ 50 kHz) aangeeft.
23 844 013
— Het DC niveau van 10-7082 (+ 4,7 V) aantekenen op
de oscilloscoop (stand DC).
— PSA verwijderen en de onderbrekingen van 2028 en
de loper van 3042 opheffen.
-- VCR afstemmen op witpatroon van een patroon-
generator.
— Met 3042 het witniveau instellen op het laatste aan-
getekende niveau (+ 4,7 V) op de oscilloscoop.
— Vervolgens met 3044 de overshoot (C) zodanig
instellen dat deze 80% is van het spanningsverschil
tussen zwart en wit (D) zie fig. 5-1.
© 3038 (niet lineaire pre-emphasis}
— 2028 onderbreken.
— Via 100 nF het signaal van de sinusgenerator 1 MHz,
2,2 Vit injecteren op 2-7052 (=0 dB).
— AC milivoltmeter aansluiten op 7-7052.
— Apparaat in positie opname.
— 3038 afregelen op + 9,5 dB (6 Viz}.
— Controle:
bij 300kHz +7 dB+t14B (5 Vtr +05 V).
bij 2MHz +9,5dB+1dB (6 Vit +05 V).