22
2.3.3.3.2.
Preparations
- Con nect the TV set to the mains via a separating transformer
- Con nect the chassis of the TV set to a proper earth
- Settings of h.f. generator PM
5324
•
Depress range button
30 . 80
M Hz
•
Depress button AM
1
kHz
•
Con nect the h.f. generator to the measuring point i nd icated i n the serv ice documentation.
The screening of the cable to the chassis should be as short as possible
•
Set control HF AMPLITU D E to maximum
- Connect the ind icator accord ing to the data g iven i n the documentation of the TV set
- Setti ngs of the TV set
•
Set the channel selector to a free channel or to a position between two channels.
By this the influence of the h.f. band·pass filters i n the channel selector on the term i nation resistor
(75
S1)
of the h.f. generator is prevented.
•
Set the contrast control to maximum contrast
•
Adjust the AGC voltage to a fixed value. I n most of the cases the connection point a nd the voltage l evel of
the pseudo ·
AGe
voltage are stated i n the service docu mentation of the TV set
2.3.3.3.3.
Checking and adjusting
For checki ng tune the i.f. range with control F R EQUE NCY (e.g. approx.
31 - 42
M H z ).
R ead the measured value in intervals and check that the val ues correspond with the recommended band-pass
curve. Bear in mind that the TV set is not overdr iven; if necessary, reduce the output voltage of the generator
by means of control HF AMPLITU D E .
However
,
the adjusted output voltage should b e constant during the measu rement.
If an i ncorrect adjustment is expected, only adjust those elements correspond ing to the test circu it. For this
consu lt the service documentation of the TV set and the relevant damping measu res, if necessary.
For more importa nt adjusting faults, it is recommended to carry out a complete adju stment in the sequence
given in the documentation and to check the compl ete band-pass curve aga in.
The sound channel of a TV set should be checked and adjusted accord ing to
2.3.3.2.
2.3.4.
DYNAMIC MEASURING METHOD
2.3.4. 1 .
Principle
( F ig.
7)
For this method, a constpnt frequency-modulated r.f. voltage is necessary. Th is voltage is fed to the test object
which is, in most of the cases, the i.f. ampl ifier of an a.m. or f.m. receiver.
The frequency-modulated signal and the frequency sweep must cover the entire i.f. range. The demodu lator of
the receiver wi l l then produce a vol tage which is proportional to the ga i n of the separate frequencies. The form
of the amplitude variation corresponds to the band-pass curve of the test object. This voltage is suppl ied to the
i n put of an osc i l l oscope (Y-input).
A
Voltage, wh ich corresponds to the frequency mod u l ation, is fed to the X - i nput. This sawtooth voltage can be
derived from the generator at output SW E E P OUT.
The resu lting curve on the screen of the osc i l l oscope represents the band-pass curve of the test object.
Note
Dynamic adjustments of i .f.- and h .f. circuits of TV sets are impossible as wobbu lating at th is frequencies is
i mpossible with this generator.
Содержание PM5324
Страница 1: ...HF Generator 100kHz 110MHz PM5324 9452 053 240 1 9499 450 05511 730801 1 01 ...
Страница 15: ...14 Fig 4 Front view Fig 5 Rear view ...
Страница 43: ...Fig 33 Front view with item numbers Fig 34 Bottom view ...
Страница 44: ...44 Fig 35 Top view Fig 36 Left side view ...
Страница 45: ...45 0 0 0 0 1 ji I I MAB225 Fig 37 Scale dri ve n ...
