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 31 1 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 still 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
3.2. 1. 1. Top cover
—
Remove both screws "A"
(Fig.
22)
-
Lift the cover at the
rear and slide it backwards from the
unit.
3.2. 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integrated circuit) has been replaced by a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 Ncm (approx. 4 kpcm) 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,
corrosive 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.
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