MAINTENANCE
4.1
Access
Electronic Wattmeter
CHAPTER
4
WARNING
Before working
on
the instrument with the case removed the
following precautions must
be
observed.
Disconnect
all external connections to the instrument
be"fore
removing the case.
After removing the case, check
care-tully to see whether any
conductors or
terminals
in
the mains circuit are exposed. Points
to
check include the entry of the power supply cable, the fuse,
the power switch, the
voltage adjusting switch and the main
connections to the power transformer.
EVERY PART
OF
THE
MAINS
CIRCUIT CAN
CARRY
DANGEROUS
VOLTAGE.
WHILE
THE
POWER
CABLE
IS
CONNECTED,
AVOID ALL
CONTACT.
The wattmeter has been designed to allow access to all the
components
by
removal of the case.
First remove the
handle by pulling
·it
outwards at each end
in
turn, thereby releasing each centre cap (see fig
4.1
).
This needs
firm pressure. Then remove, with a Posidrive
No
2 screwdriver,
the four screws
on
each side of the case (two
.of
which are
in
the
handle boss)
Fig 4.1
The top and bottom halves of the cover can then
be
lifted
off.
The chassis formed by the PWB and front and rear panels
is
strong enough for normal handling during maintenance.
23
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