Application; Checking The Tuner(S) Of The Receiver - Philips PM 5508 Operating Manual

Pal-colour pattern generator
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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.

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