Philips PM6302 Instruction Manual page 34

34
3.1.5. Power supply
The voltage rectified with 416 is stabilized and balanced to zero by means of zener diodes 417 and 418,
Transistors 310 and 311 are power amplifiers. Transformer 761 delivers the voltage for rectifier 416 and,
from a totally screened winding, that for rectifier 415.
3.2. GAINING ACCESS TO PARTS
The opening of parts or removal of covers, is likely to expose live conductors. The instrument should therefore
be disconnected from all voltage sources before any opening of parts or removal of covers is started.
During and after dismantling, bear in mind that capacitors in the instrument may stil! be charged even if it
has been separated from all voltage sources.
Use a well-fitting screw-driver to dismantle the instrument to prevent the screws for damage,
3.2.1. Dismantling
32.1.1. Top cover
— Remove both screws "A" (Fig, 22)
— Lift the cover at the rear and slide it backwards from the unit.
32.1.2, Bottom cover
— Remove both screws B" (Fig, 22}
— Lift the cover at the rear and slide it backwards from the unit.
3.2,2, Electrical components
If an electrical component (resistor, capacitor, transistor or integrated circuit) has been replaced by a new
one, the relevant part of the circuit must be checked in accordance with chapter 3,5,
3,2.3.Mounting the linear scale and the potentiometer
~ Front panel must be flush
— Screw linear scale with a maximum torque of 40 Nem (approx. 4 kpem} onto the front panel (a higher
torque may cause deformation of the material).
— Fit the pre-mounted potentiometer {with suspension and protection against being turned out of position)
into the drilled hole provided. Slide the holes of the suspension arms onto the pins of the spacers.
— Turn potentiometer with a screwdriver (maximum width 4 mm) to the left stop.
— Set pointer exactly to the extreme left division {.01), beyond mark A respectively,
— In this position fasten the potentiometer shaft to the drive by means of the two grub screws.
— Set printer to the extreme right position and back again to the extreme left position (Do not use force).
— Pointer reading and calibration reading must coincide; otherwise, repeat adjustment.
~ Securely tighten both grub screws.
— Check scale drive for free movement and smooth running.
— Fit textplate and check again scale drive.
— Secure both grub screws with paint.
3.3. MAINTENANCE AND SERVICE
The RCL-bridge PM 6302 requires no maintenance because the instrument contains 'no components which are
subject to: wear.
However, to ensure reliable and faultless operation, the instrument should not be exposed to moisture, heat,
corrasive vapours and excessive dust.
Service: If service work must be performed, the following points should be taken into account to avoid
damage of the instrument.
— In case of measurements on a switched-on instrument proceed carefully to avoid short-circuits by means of
measuring clips or measuring hooks.
— For soldering use absolutely acid free soldering tin
— For all soldering work on the printed circuit boards, use a miniature soldering iron (35 W max.) with a thin
cleaner or a vacuum soldering iron.