Philips PM6302 Instruction Manual page 36

36
_ 3.5. CHECKING AND ADJUSTING
Tolerances given in this chapter apply only in case of newly adjusted instruments. The values may differ from
those given in chapter 1.2. Technical data.
The adjusting elements, their location and function are mentioned in chapter 3.4.
Any adjustment, maintenance, and repair of an instrument which is opened whilst connected to the mains
should be avoided as far as possible and, if inevitable, shall be only carried out by skilled personnel familiar
with the risk of shock involved.
3.5.1, General test
3.5.1.1. Power supply
— Check that the current consumption is < 20 mA at 220 V mains, 50 Hz.
~ Check that the filtered voltage across capacitor 528 ties between +19 V and +22.V; and across capacitor
631 between —19 V and —22 V (mains voltage 220 V).
— Check that the stabilized voltage across capacitor 530 lies between +13.6 V and +15.4 V and across
capacitor 533 between —13.6 V and —15,4 V.
— Check that the filtered voltage for DC-operation across capacitor 527 is 1.4 V + 0.2 V (mains voltage 220 V)
— Depress button R
— Check the polarity of test sockets !-E
— Depress button C
~— Connect an external voltage to sockets DC-BIAS.
~~ Check the polarity of test sockets 1-E
35.1.2, Oscillator
— Frequency check: button D not depressed; f = 970 Hz + 19 Hz
button D depressed; f = 97 Hz + 2 Hz
— Set range switch to position 10 nF
— Depress button C
— Measure the amplitude, at 100 Hz and 1 kHz, between points 7 and 11 of push-button switch 801A,
Right value: between 650 and 800 mVrms.
— Set range switch to position 1 uF
-- Check that the amplitude, at 1 kHz, is 1/10 of the value measured with range switch in position x10 nF
(measure also between points 7 and 11}
— Supply a voltage of 7 Vrms to sockets EXT.-AC of the bridge
— Check the amplitude between points 801A/7 and 801A/11 at 100 Hz; 5 kHz and 20 kHz.
Right value: between 600 and 750 MV¢ms
3.5.1.3. Indication amplifier
— Depress button R
~ If detuning the bridge an ascillogram as shown in fig. 17 will be visible at the + side of capacitor 512
f=fmains. MA825
Fig. 17. Voltage on + side of capacitor 512
— Depress button € {button D not depressed)
— Hf detuning the bridge, on the + side of capacitor 512 there must be a 1-kHz-sine wave the tops of which
are slightly deformed.