Philips PM 5509 Bedienungsanleitung Seite 22

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3.@ This pattern can be used to check whether a T.V. receiver suffers from excessive interference due to
the colour subcarrier. Moreover can be checked that no interference appears between sound and
colour carrier.
4.0 This pattern gives the possibility to align the chroma-writing current of the video head.
This alignment is critical. The total writing current {for PHILIPS N1500) consists of the luminance
current (which is about 25 mA) and the chroma-writing current (1 mA; with the red pettern).
The luminance writing-current magnetizes the tape very strongly and works on the principles as the
H.F. bias in an audio-recorder.
G. PATTERN 7
"White"
This pattern consists of a 100 % white signal with alternating burst (see Fig. 18).
1.@ Check the picture for constant brightness over the entire screen (no hum, etc.).
2." Check for a good ''white-D" of the colour-picture tube (re-adjustment is required after e.g.
replacement of the picture tube), This should be done with control CHROMA in position NOM. Some
colour receivers switch automatically from ''mono" white to "'colour''-white (white-D).
This, the so-termed preferred-white adjustment, can be checked by setting contro! CHROMA from
NOM to 0 % and back.
3.8 This pattern is also necessary to check and readjust the limiting of the beam-current of the colour
picture tube. For details about this adjustment, refer to the Service-Notes of the receiver under test.
4.0 For video recording this pattern, containing a 100 % white signal, is ideal to align the luminance-writing
current.
Secundly this pattern can also be used for adjusting the FM demodulator (white-level adjustment).
H. PATTERN 8
"Dem"
Special bar pattern (4 vertical bars and horizontal reference bar).
This pattern is especially designed for checking the PAL-delay line with the PAL-switch, the demodulators
and matrix circuitry. (see Fig. 19).
Bar 1 contains (R—Y) and (B—Y) information where (G—Y) = 0. This bar can be used for alignment of the
G—Y-matrix.
Bar 2 and the horizontal reference bar contain no colour information, thus only a luminance signal.
1.@ Checking the PAL-delay line circuit and the switch.
The (R—Y) information in bar 3 is N.T.S.C. coded i.e. the polarity of the (R—Y) signal does not change
each line. The burst signal on the other hand is PAL-coded and so ensures normal operation of the
PAL-switch in a colour receiver. This Dem" pattern is designed for on-the-screen alignment of the
64 us chrominance delay line in amplitude and phase.
Venetian-blinds will appear when adjustment is needed. One can distinguish between amplitude and
phase faults by observing in which bar these venetian blinds appear.
— Amplitude fault (see Fig. 20):
the third bar gives every line the same (R—Y) information. A fault in the delay line gives a difference
in amplitude between the direct and the delayed signal.
This will be clearly visible as a venetian blind effect in bar 3.
Do not look at the colours but only for the appearance of the venetian-blinds effect in the third bar.
— Phase fault.
a Phase fault will cause venetian blinds in bar 1 and 4. The fourth bar contains only (B—Y)
information which is alternated 180° each successive line.
The (B—Y) result will be zero if there is no phase fault in the delay line. If there is a phase difference
between the direct- and the delayed signal this will result in a (R—Y) component. This fault will
appear in the first and fourth bar (see Figs. 21 and 22).