Philips PM 5508 User manual

9499 490
0491 1
PHILIPS
PAL
-COLOUR
PATTERN
GENERATOR
P M 5508
(9449 055 080.1)
1 t
/369/302/03/04

i
1
1
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PHILIPS
1
i
A
Operating manual
PAL
-COLOUR PATTERN
GENERATOR
9499 490
04911
P M 5508
(9449 055 080.1)
11
/369/3/02/03/04
w

2
Contents
GENERAL
I.
Introduction
II.
Technical data
III.
Accessories
IV.
Description
of the block
diagram
OPERATING
INSTRUCTIONS
Page
5
7
11
12
V.
Installation
19
A.
Adjusting
to
the
local
mains
voltage
19
B.
Earthing
19
C.
Connections
19
VII.
Application
23
VI.
Operation
21
A. Pattern 1 :
"Cf1ECKERBOARD" 24
B. Pattern 2:
"WHITE"
28
C.
Pattern
3:
"RED"
29
D. Pattern 4 :
"GREYSCALE"
31
E.
Pattern
5: "DOTS"
33
F. Pattern
6:
"CROSSHATCH"
35
G.
Pattern 7 : "DELAY"
38
H. Pattern 8: "PHASE"
44
I. Pattern 9: "MATRIX"
50
J.
Pattern
10 : "COLOUR BAR"
52
K. Adjusting with
the oscilloscope
58
Addresses 81
© N.V.
PHILIPS' GLOEILAMPENFABRIEKEN -
EINDHOVEN -THE
NETHERLANDS

3
List of
figures
Page
IV -1 Block
diagram 15
VI -1 Controls
and
sockets
21
Vil-1
"CHECKERBOARD" -pattern
24
VII -2 Incorrect
vertical amplitude
and linearity
25
VII
-3
Incorrect
centring 26
VI I -4 "WHITE"
-pattern
28
VII -5 "RED"
-pattern
29
VII
-6
Typical purity error 30
VII -7
"GREYSCALE"-pattern 31
VII -8
"DOTS"
-pattern 33
VI I -9 Detail of incorrectly converged picture
34
VII -10 "CROSSHATCH"
-pattern
35
VII -11 Incorrect horizontal dynamic convergence 36
VII -12 Picture
detail
incase
of
incorrect dynamic convergence 36
VII -13 "DELAY" -pattern 38
VII -14
Vectorscope display
of
the
"DELAY" -pattern 39
VII
-15 Picture
detail showing the "Venetian blinds" effect 40
VI I
-16
"Venetian
blinds"
in bar
3
(detail) 41
VII
-17 "Venetian
blinds"
in bar 2 (detail)
41
VII
-18
"PHASE" -pattern
44
.~
VII
-19 Vectorscope display
of
the
"PHASE" -pattern 45
VII
-20 Incorrect
subcarrier phase to
the
(R -Y)
demodulator
46
VI I -21
Incorrect
subcarrier phase to the (B -Y)
demodulator 47
~.. VII -22 Incorrect subcarrier phase to
both demodulators
(R-Y)and (B -Y)
48
VII -23
"MATRIX"
-pattern 50
VII -24 Vectorscope
display
of
the
"MATRIX" -pattern
51
.r
VI I -25
"COLOUR BAR"
-pattern 52
VII
-26
Vectorscope display
of
the
"COLOUR
BAR" -pattern 53
VII -27
Blue-colourdifference-signal of "COLOUR
BAR" -pattern 54
-- VII
-28
Red-colourdifference-signal of "COLOUR
BAR"
-pattern
55
VII
-29
Green-colourdifference-signal of "COLOUR
BAR" -
pattern
56
VII
-30
Correctly adjusted
delay -Fine
58
._..
VII -31
Amplitude
error in delay -line
59
VII -32 Phase
error
in
delay -line
59
VII -33
Both demodulators
adjusted
correctly
60

4
Page
VII
-34 Only (R
-Y) demodulator
adjusted
incorrectly 61
VII -35 Only
(B -Y) demodulator adjusted
incarrectly
61
VII -36 Both
demoduUators adjusted
incorrectly
61
VII
-37 Correct (G -Y)
signal
62
VII -38
Incorrect (G -Y)
signal 63
Circuit diagrams
66,
etc.
IMPORTANT
In
correspondence concerning this instrument, please state the type-, serial-
and instrument
number
as
given on
the identification plate at the rear of the instrument.
t
1
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1
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5
U
GENERAL
I.
INTRODUCTION
The
PHILIPS
PAL
-colour
pattern generator PM
5508 is
an all solid state, mains
supplied instrument. bt is
intended for use
when installing,
fault
-tracing and re-
pairing colourTV sets operating
according
to the
PAL
systems G and
I
and
blackf
white TV sets
operating according
to
the
625 lines
CCIR
systems
B, I,
G and
H.
The PM 5508 is suited for use
with colour -TV receivers of
various principles,
the
circuits of which could
differ in many ways, e.g. R -
G -
B
control of
the picture
tube instead
of control with (R -Y), (G -Y) and (B
-Y)
and
Y, separation of lumin-
ance and chrominance
signal in the video stage instead of with the aid of an
additional I.F. chroma
detector,
etc.
Therefore the instrument is
designed so
that it
produces ten test
signals, by
means
of which the complete
receiver
performance
can
be checked by
simply
observing
the patterns
on the
screen.
A complete test
will only
take a
few
minutes.
If during
this test it is
observed that the receiver requires realignment,
the latter
can easily and accurately be done with the aid of the generator signals.
Re
-adjustments of the delay -line circuit, the chroma-demodulators and the ampli-
tude -ratio
of the colour -difference signals
can even
be carried out by simply
using the screen of the receiver as
an
i-ndicator.
The instrument moreover has the
following
features:
—
The
RF output
signal
covers
the
VHF-
and
UHF
ranges.
—
Presetting of 4 channels i~n the
VHF range and any 4 channels
in
the UHF
range; instead
of
one
VHF-chamnel,
the IF
vision carrier can be preset.
— RF
output
signal
continuously adjustable
and sufficiently high to supply
several receivers
simultaneously.
— Sound
carrier can be
switched on/off.
Sound
carrier can
internally
be
modulated with 1 kHz.

6
— Burst amplitude
continuously adjustable between
0 and 200%, fixed
nominal
position.
—
Composite
1
Vp-p video
signal externally
available.
"LINE-"
and
"FRAME
SYNC."
signals externally available
for triggering
purposes.
—
Handy,
small
and light -weight instrument suited
for
workshop
as
well
as
mobile service.
a

7
-
II.
TECHNICAL
DATA
•.,
..
Properties expressed in
numerical
values with
tolerances stated, are guaran-
teed by
us.
Numerical
values
without
tolerance are intended for information
purposes only and indicate
the
properties of an
average instrument.
Vision carrier:
,~ IF
38.9 MHz
Band I 55. . .
70
MHz
Band III 173. . .225 MHz
Band
IV/V
470. . .850 MHz
"'~ Push
-buttons enable
presetting of any
4
UHF
channels and 4
VHF
channels
or
3
VHF
channels and the
vision IF carrier.
..,
Spacing
of vision
and sound carriers:
PM
55088:
6.0
MHz
(CCIR
system I;
PAL system
I)
-~ PM
5508E: 5.5 MHz (CCIR
systems
B,
G and H;
PAL system G)
Frequency drift of sound subcarrier: ± 0.1 % {10° . . . 40°
C)
.~,
.~
Video modulation:
Modulation
AM,
negative
Residual carrier
i 5% at 100%
white
Vision
modulator balanced diode type; max
unbalance 5%
Differential
phase <
5 °
Sound modulation:
...
Modulation
FM
Sweep =~
50
kHz
Distortion
< 3%
Internal modulation
1
kHz, sine
wave
.~.
Modes
of operation
sound
carrier off
—
unmodulated
— modulated
with
1 kHz

8
Encoding
System
PM
55088:
PAL -I
PM
5508E:
PAL -G
Subcarrier
4.433619
MHz
Frequency
drift of
Subcarrier ± 20
Hz (10 °
.. .
40 °
C)
Burst
width
approx. 10
cycles
of
subcarrier
Burst
ampl itude
"NOM"
position:
equal
to
sync.
signal.
Burst
phase
Adjustable: from
approx. 0%
to 200%.
line
sequential :
180° ± 45 °
Burst
position
5.6 fps
after
leading edge
of line sync.
pulses
Chroma
modulators
balanced diode
type
Chroma
bandwidth
1.1 MHz
(3dB)
Group
delay
precorrec-
tion
of Chroma
signal — 175
ns
Colour
matrixing
Y
=
0.30
R + 0.59 G +
0.11 B
Patterns
"CHECKERBOARD" 6 x 8
black/white squares,
accurately
centred.
"WHITE" 100%
white
signal with PAL
-alternating burst.
"RED" fully saturated red
signal with PAL
-alternating
burst.
"GREYSCALE" staircase
signal with
8
identical
steps.
"DOTS" white
dots;
location
corresponds
to the
intersections in the Irosshatch
pattern.
"CROSSHATCH"
11
horizonta! white lines;
width: on line per
field
15 vertical
white lines;
width:
200 ns.
The horizontal and vertical
white lines form
black
squares, accurately
centred.
J
J
LJ
u

n
9
A
A
A
n
w
n
A
n
n
n
"DELAY"
"PHASE"
"MATRIX"
"COLOUR BAR"
4 vertical
bars:
146° : (G
-Y) =
0,
180° : (R
-Y) =
0, luminance 40%
grey
NTSC
encoded, however with PAL -alternating
burst.
same bars as "DELAY" with PAL -alternating
burst.
However,
upper part:
PAL
encoded
with
reduced
saturation,
and lower part: only chroma
during
the "positive" PAL -lines, where burstphase
135°.
same bars as
"DELAY" with PAL
-alternating
burst,
however, completely PAL encoded.
75%
-contrasted pilture.
Upper part:
colour bar
signal
with
8
vertical bars: white,
yellow, cyan,
green, magenta, red, blue
and
black. Lower part:
white.
Bar
Relative
luminance
amplitude
Chroma
phase
Relative
chroma
amplitude
White 0.75 — —
Yellow 0.67
167°
±
0.33
Cyan 0.53
283° ±
0.47
Green 0.44
241 ° ±
0.44
Magenta
0.31
61 ° ±
0.44
Red
0.23
103° ±
0.47
Blue 0.08
347° ± 0.33
Black
0 — —
Synchronisation
and
blanking
Line frequency
Field
sync. pulse
15625Hz±0.1%
width 2.5
lines
(no
inverted line pulses
during
field sync.
pulse, no
equalizing
pulses, no
interlacing)
n

10
Line
sync. pulse
Field
blanking
Line
blanking
Total field
period
Active field
period
Total line period
Active line period
Set-up
between
black
level and
blanking
Sync. to picture ratio
Outputs
Socket "RF"
For UHF
For VHF
Output impedance
Amplitude ratio
vision
to sound carrier
Connectar
Socket
"VIDEO"
Voltage
Polarity
Output impedance
Connector
Sockets
"SYNC."
Signal
width
frontporch
blackporch
24 lines
12.8
µs
312 lines
288 lines
64 us
51.2 ,us
5 %
30:70
4.8 ,us
1.9
,us
6.1
us
20
mV *), if
loaded with 75
52
or 40
mV *), if
loaded
with
300
52
(via
matching
transformer
75
52
~
300
S2)
continuously adjustable
15
mV *), if loaded with 75
2
or 30
mV *), if
loaded with 300
S2
(via
matching
transformer
75
S2 -~
300
52)
continuously adjustable
75
52
4:
1
BNC, female
1 Vp-p, if loaded
with 75
S2
white
positive —sync.
negative
75
S2
BNC,
female
optionally:
— line frequency pulses
—
field frequency
pulses
to be selected
with switch
"SYNC."
')
RMS-value
of the vision carrier during the peaks
of the
modulation envelope.
r
r
r
r
r
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11
.~
~.
Amplitude
Polarity
Output
impedance
Connectors
Supply
Mains
voltage
Mains
frequency
Power
consumption
Safety fuse
Mechanical
data
Dimensions
'-" Height x
width x depth
Weight
_
III. ACCESSORIES
5
Vp-p,
unloaded
positive
10
kn
4 mm banana
sockets
115
V
or
230
V, ±
20%
50-60
Hz
15
W at 220
V
200
mA, delayed action type
Modular
cabinet
195
x 305
x
275
mm
(width:
4
units)
6.1 kg
1 Operating
manual
1 Mains
flex
1
RF cable
with, only with PM 5508E, a
matching
transformer 75
52 ->
300
52

12
IV.
DESCRIPTION OF THE
BLOCK
DIAGRAM
(See
Fig. IV -1)
To
obtain
a constant
ratio
between line synchronising pulses, field synchro-
nising pulses and the various
patterns, the
circuits of the instrument are
controlled
by
a master
oscillator. The frequency
of
this
oscillator (312.5 kHz)
is
divided by
means of a 2 :
1 divider in order to
obtain the pulses "a",
which
control
the
horizontal information in the patterns.
This divider is followed by
another 2 1 divider and a 5
1 divider in order to
obtain
pulses
of line
frequency ("Ib" and "Is").
Furthermore, the line
frequency is
successively divided by 2, by 4, by
3,
and
by 13
in
order to
obtain
pulses
shaving the field frequency ("fb" and "fs").
These dividers also
supply
pulses to
control the
vertical information in
the
patterns ("24
I", "312 I", from which are derived "~ b" and "96
I").
The luminance signal, the black/white patterns, the
convergence
patterns
and
the composite
sychronising
and
blanking signal are generated on the basis
of the afore
mentioned
horizontal and vertical control pulses.
These
signals are added
in
the luminance
-sync. -blanking adder and passed
on,
via
the
delay Fine,
the
video
amplifier, where the
composite luminance
signal
is added to the chrominance
signal.
The delay line (0.375 ,us)
com-
pensates for
the •time delay which arises
when
the colour signals are encoded.
The R, G, and B
signals
are
generated
in
the colourbar generator. This gene-
rator
is followed by
a
matrix, "adding" the R,
G, and
B
signals
in
such a way
that the correct
Y,
(R -Y), and (B -Y)
signals
are
obtained. The step
signal
(Y')
of the greyscale signal
is also generated in this matrix.
The colour
subcarrier signal
is supplied by acrystal-controlled oscillator. The
phase of
the subcarrier
to the (B -Y) modulator
is shifted 90° in a phase
shifting
circuit, in order
to
obtain
the
correct quadrature of (R -Y) and (B -Y).
In
a PAL switching
circuit the
phase
of
the subcarrier to the (R -Y)
modulator
is inverted line
sequentially, in order
to obtain the PAL encoding.
The PAL
switching
circuit
can
be cut out during
the moments,
that
the
generator has
to
produce an
NTSC encoded signal
(test signal "DELAY").
During this
signal,
however,
the PAL switch
actually
operates briefly during
the line
backporch
to
produce the PAL
-alternating
burst. This is
controlled by the " 2 I' "
pulses. The
colour
-deference
signals and the
burst
keying
pulses {the
latter
are
derived from
the
"Is" pulses) are
applied to
the
(R -Y)
and (B -Y)
modula-
tors.
These
modulators are
balanced
modulators together supplying
the
chromi-
nance signal in
which
the carrier
wave
has been
suppressed. The chrominance
signal
is
added to the
luminance
signal in
the
video amplifier.
r

13
The sound subcarrier is generated
in
a 5.5
MHz
(6
MHz in
the
B
-version)
oscillator.
Via
a switch, this subcarrier
can
be frequency
-modulated
with
1 kHz by means
of a modulator, operating according
to
the
diode switching
principle. This
subcarrier oscillator itself can be
switched
off if
desired.
In
an
adder stage the sound subcarrier is added to the composite video signal.
From there it is applied to
an
RF modulator and,
via
an RF
attenuator, to
output
socket
"RF". The
instrument is
provided
with
an
stabilised power supply
with
short-circuit
protection
circuit.

15
r
Master
o scillatar
312,5 kHz
117
S
haper
U2
Subc.
oscillator
U4
1
PAL 90 °
~►
switch
faseshift
0/180°
U4 U4
SK4
►~•
' Po wer
I
on"
l 1
R -Y mod.
B
-Y
mod.
Line
information
2:1
div.
9e n.
U2
AND
gate
'J2
2:1
Div.
U2
Colour
bar
gen.
o< co m m
>
Y
2
S
Line
blank.
gen.
51
div
U2
1
Matrix
s
0
.~
w
(R) ~
Stab. ~ +6V
~.3121(viaSK3)—►
SQ~100%
power
—►
OV R~
Sat.
supp.
U1
—r.-6V
G— ~
U4
Matrix for
burst
and
testpatt ~~
Line sync
gen.
U2
—►
(G)
Matrix
for
burst and
testpattern
U4
~~
J .o
iu
C
m
2:1
Div.
Burst
key
gen.
U4
1
s
a1
~.
~
in
11
R -y
modulator
U4
U2
+6 V
—r.
B
-Y
modulator
U4
m
4+1
Div.
U2
(8l
31
Div,
U
_1
2
124
M
m
9urstampl. ~ ~
R1/0-200% ~
g
SK2 100%
T
'>.
1 ~
Chrominance
adder
Luminance
ampL
U2
13:1
Div
1
m
—i
Field
blank
gen
N
2~
Field sync
9~
Y3 ~
1
a
Z
y '
1`
' 1
v = c o 0
-
~
~ m rn
b
> >
m
o, ~. Z_ 2
a 2 n
co a
~1~1111111
Gate circuit
for
BI~Wh
pattern
U2
U3
in~a
w
~~1~11
Gate circ.
for
ync/blank
<11
Luminance
sync blank
adder
U2
Y-
Delay
U4
1
L
Video
ampl.
U4
1
Y
N
0
n
Frame
infomnotion
gate
U3
1
2
a
I
+
1
■
41
Div
1 _~
U]
D7
Ol
2
l000 H:
oscillator
U4
3
'Line"
'ls►—~.
'fs'~~
"Frame"
SKS
FM
mod.
U4
Soundsubc
osc.
U4
l
Modulator
` U5
~~
SK1
'Mod'
_/ ~~+6V
SK7
"Unmod."
RF
osc.
US
i
R2
'RF
Output' s
I
I
J
PEM 4038
1
BUl
Sync •
~p1BU2
I
I
J~~
BU4
RF
out"
~
BU3
°Video
out "
Fig. IV -1.
Block diagram

w
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A
A
A
.►
.~
A
...
19
OPERATING
INSTRUCTIONS
V. INSTALLATION
A. Adjusting to the local
mains
voltage
The instrument can be used with mains
voltages
of
115
V
a.c. ±
20
and 230
V
a.c.+ ?_0 %.
If
the instrument has to be adjusted to another
mains voltage, resolder
the connections to the primary
windings
of
the
supply
transformer
as shown
in
the
sticker on
the transformer.
To gain
access to the
supply
transformer
and fuse:
— Remove the bottom
plate (two screws),
the transformer
-connections are
then
accessible.
—
Remove the two screws holding
the printed wiring
unit which
should
then
be hinged out.
—
The fuse (200
mA,
delayed)
is
then
accessible.
B. Earthing
Earth the
instrument
in
accordance with
the local
safety
regulations. This
can
be done via the
mains
flex,
as it is
equipped with a
plug
with
rim -earthing
contacts, or via the earth -screw
at the rear
of the
instrument. Not only
the
metal cabinet is then
earthed but also
the "common" of
the
circuit.
Avoid double earthing.
C.
Connections
RF:
—
Connect the
generator to
the
mains by means of
the mains
flex
suppl ied.
—
Connect socket
"RF" to the receiver to be
checked by means of
a RF
cable and, if
necessary, via the 75
S2
~
300
52
matching
transformer.
— The
measuring set-up
then
is
ready (see
the section
"OPERATION"
on page 21).
-.
t
+~

20
VIDEO:
Circuits
requiring an
encoded
colour
video
signal or
a black/white
video
signal (e.g. monitors, decoders, video tape -recorders, etc.)
should be
connected to socket "VIDEO" by means
of
a
coaxial
7552
cable. A positive
video
signal with
an
output impedance of 75
S2
can
be taken from
this socket.
If loaded with 75
5?,
the output amplitude is 1 Vp-p.
SYNC.:
If an oscilloscope is to be triggered externally for
some
measurements,
connect
the sockets
"SYNC."
to the external trigger
input of
the
oscil-
loscope.
Set
switch
"SYNC."
to position "LINE" in case
this
triggering
is
to
take
place
in the line sync. -pulse -rhythm and to position
"FRAME" in
case
of
triggering with field -sync. pulses. The polarity of
the trigger
pulses is
positive.

21
VI. OPERATION
1
1
A
A
A
1
1
1
A
1
A
1
The following
is a
description of the procedure for tuning the generator
to a
colour receiver
and for
adjusting
the "customer controls" of the colour
receiver to their proper settings. It is obvious
that
this procedure probably
cannot be completed
if
the
receiver
is defective.
—
Make the connections as
indicated in section
"INSTALLATION",
part
C:
"Connections-RF", page
19.
—
Connect the colour receiver to the mains.
Warning
In
most
IV -receivers equipped
with
valves, the heaters are series con-
nected;
one pole of the mains is
then
connected direct to the chassis.
Therefore,
before measuring on the receiver, connect
it to
the
mains via a
separating transformer.
—
Switch
on
the colour
receiver.
—
Switch on the generator
(switch
"POWER" to
position "ON").
One of the
channel
scales
will
be
illuminated, depending
on whether aVHF-
or an UHF
-button
is depressed.
— Turn control "BURST AMPL."
ul ly anti
-clockwise (switch
to position
"NOM", clicking
sound!).
Switch for sound
carrier on/off and ° ° ~ * ' ~*~
modulation
on~off
~\~°
„,_, ~ - „, ~— ~ ~ ~ ~. ~ ~~
Push -buttons
for
UHF -channel selecting
Pattern selector
switch
Mains
switch
Switch
for
selecting
trigger pulses
Output
sockets
for sync.
signal
~~~~%~~L~O~IC7
Fig.
VI -1. Controls and
sockets
Control for
burst
amplitude
Fush-buttons
for VHF -channel
. selecting
Control for RF
output voltage
RF output
socket
Video
output socket

22
Set
control "RF
OUTPUT"
to "10
mV".
Depress
switch "COLOUR BAR" and set
switch "SOUND
CARRIER"
to
position "MOD."
Note:
With
the
exception of the colour settings, the
tuning,
etc.,
of
the black/white
receiver to the generator is identical to the described procedure for
colour
receivers.
In
this
case, however, use the "CHECKERBOARD"
-pattern.
Tune '`) the generator to the
channel
to
which the receiver is adjusted (the
receiver should not be tuned to one
of the local transmitters). As the
generator produces a double sideband
RF signal, be sure to tune to the
correct
sideband (the one that is highest
in frequency), i.e. first set the
generator to a
channel
thas is
lower than the one to which the
receiver
is
adjusted
and then tune the generator to the
receiver.
The first sideband
"encountered",
is
the
correct
one.
The
receiver can
also
be
tuned to the
channel setting of the generator.
In
that
case the receiver should first be set to a higher
channel than the
generator, etc.
Carry out the fine
tuning
adjustments so that
the picture on the
receiver
contains
colour,
while at the
same time there is no "sound
in
the
picture".
Set the
generator
to
the "GREYSCALE"
pattern.
Adjust controls "BRIGHTNESS"
and "CONTRAST" of the
receiver
to
obtain correct settings, i.e. the left vertical bar should be white and the
right one should be
black,
while the bars
in between
should
show six
grey level steps increasing
in
darkness from left to right.
Set
the
generator
to
the "COLOUR BAR" pattern.
—
Adjust
control "SATURATION" of
the
receiver
to
obtain
the correct
setting, i.e. :
first
turn
it
fully
anticlockwise and
increase
the
saturation
until
the
green
and the blue dots
in
the red bar just
disappear.
— The "customer
-controls"
of
the receiver then are properly adjusted.
') The push -buttons for channel selecting can
be pre-set to any channel within
the
range of the
generator. To
change
a presetting, turn
the
button
while it is depressed. The dial
pointer wi l l
indicate the selected channel .

w
w
w
A
A
A
A
A
A
A
1
A
1
A
1
23
VII.
APPLICATION
The
generator supplies ten
specially
selected test signals for colour
as well as
for black!white.
All
these signals
can be
switched
on
by means
of
push
-buttons,
which
are
arranged for
obtaining
the signals
in
the optimum sequence for testing.
First the basic
blackiwhite tests are made and then the special colour
tests.
•
The sections
marked with a red dot are
for colour
-receivers
only
while
the
•
others,
marked with a
black
dot,
are for colour as well as for
black/white
receivers.
The
description
on
the
following pages is intended to give the user an impression
of
a
checking
procedure for receivers. At the same time an explanation of
the
colour patterns is
given in small print.
CHECKING
THE TUNERS)
OF THE RECEIVER
Due
to a modification
in
the
VHF tuner, the frequency limit at the beginning of
Band
I
has
been shifted so
that
the
range around
channel 2 (CCIR, system B)
is replaced by the IF range
common for TV receivers (around 38.9
MHz).
The
indication "2" on the VHF channel
scale
is
therefore replaced by the indication
"IF".
The
user can now determine
whether
the
incorrect functioning of
the
receiver is
due to a
defect
in the channel selector.
Procedure
If, when following the
procedure described in chapter
VI "OPERATION",
there is doubt
whether
the
incorrect
functioning of
the
receiver is
due
to a defect
in
the channel selector,
proceed as follows:
1. Depress
button "BL/WH" (checkerboard) and set
switch "SOUND CARRIER"
to
position
"UNMOD.".
2. Connect socket
"RF"
via a
coaxial cable (without matching transformer) and an isolating
capacitor,
to the
input of the first IF stage
of
the
receiver.
If necessary,
temporarily unsolder
the IF
connection of this stage with the channel selector.
3. Tune the
PM
5508 to the
IF of the
receiver,
ensuring that the receiver is not overloaded
(use control "RF OUTPUT"
of
the
PM 5508).
4. If
the
receiver does operate
properly yet,
the
defect will
be located
in the channel selector.
We would like to emphasise
that this IF
signal
of the PM 5508 should not be employed for
any purpose other than described above.