Checking And Adjusting - Philips PM2521 Service Manual

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62
3.
CHECKING AND
ADJUSTING
WARNING:
Before switching-on, ensure that the instrument has
been
installed in
accordance with the
instructions outlined in Section 5 of the Operating Manual.
The
opening of covers or removal
of parts, except those to which
access can be gained
by hand
is
likely to
expose
live parts,
and
accessible
terminals
may
also be liw.
The
instrument
shall
be disconnected from
all
voltage sources before any replacement
or
maintenance and
repair during which the instrument
will be opened.
If
afterwards, any adjustment,
maintenance or repair of the opened
instrument under voltage
conditions
is
inevitable,
it shall
be
carried
out only by
a skilled person
who
is
aware of the
hazard involved.
Bear
in
mind
that capacitors
inside
the instrument may
still
be charged even
if
the instrument
is
separated from
all voltage sources.
The
tolerances
in this
chapter correspond to the factory
data, which only apply
to a completely re-adjusted
instrument. These
tolerances
may
deviate from those mentioned
in
the Technical Data. (Chapter
2. of
the
Operating Manual).
For
a complete re-adjustment of the instrument the
sequence
in this
chapter should be adhered
too.
When
in-
dividual components,
especially semi-conductors
are replaced, the relevant section should be completely
re-
adjusted.
To
calibrate this measuring instrument only
reference voltages and measuring equipment
with the required
accuracy should be
applied.
If
such equipment
is
not
available, comparative measurements can be made
with
another
calibrated
PM2521.
However,
theoretically in
extreme
cases,
the
tolerances
may
leave
some room
for doubt.
The
measuring arrangement should be such
that the measurement
cannot be affected by
external influences.
Protect the circuit against temperature
variations (fans, sun).
With
all
the
measurement
the
cables
should be kept
as short
as possible; at higher frequencies co-axial leads
should be
used.
Non
screened measuring cables
may
act as serials so that the measuring instrument
will measure
LF
voltage
values or hum.
voltage.
Before checking and
adjusting,
remove
the top-cover. Make
sure that the cable from the power supply
is
connected with
X802.
In the software there are two subroutines which
are used for adjusting the PM2521. To
call
these subroutines
short
circuit
TP10 and TP1
1
for one second
(first subroutine)
and
repeat
it
for the next
subroutine. After
using these subroutines the PM2521 should be
reset. (Switch the
PM2521
off
and
on).
Fig.
46. Adjusting elements