Table of Contents
Advertisement
MODEL 6OOA ELWPFtOMfZ!CEZ
SECTION VI - UACATNTENANCE
MAIN'lWANCE
No periodic
maintenance is required other than checking the batteries
as provided for by the front panel control.
The method of performing
these checks is outlined
in Section III-E.
The calibration
of the voltmeter
is set by R41 located on the horison-
tal chassis carrying
Bl, B3 Bh and B5. This is set at the factory
and should not require
adjustment.
If recalibration
is performed, an
accurate
voltage
source should be used.
A.
Trouble Shooting
The circuit
is completely described in Section IV.
Study of that
section will
facilitate
any trouble
shooting.
The most usual trouble encountered is that on the most sensitive
volt-
age range, with the input shorted, it is not possible to bring the
meter pointer
to zero.
However before assuming that the instrument is
at fault
make sure that resetting
the COARSE ZERO control at the rear
of the instrument will
not oring the instrument back into balance.
If this does not work it will
be
necessary to remove the instrument
cover to gain access to all circuitry.
The instrument cover is re-
moved by unscrewing the three screws on both sides of the instrument
and lifting
the cover upward.
With the cover removed, follow this
procedure:
Short floating
ground to output ground to remove the negative feed-
back.
This is most conveniently
accomplished by shorting the two
ends of the FAST-NORMAL switch on the rear panel.
In this condi-
tion the instrument will
become very sensitive
and, in operating
the zero control,
the meter will
be very difficult
to hold on
scale.
However, t&indication
that the circuit
is operating
satisfactorily
is that it is possible to swing the voltage through
the'correct
operating point as indiczited on the voltage-resistance
diagram.
Now with the MULTIPLIER switch at .Ol volts,
proceed to check the
operating points of the tube electrodes.
Regardless of the condition
of the amplifier
balance, the filament
or cathode, and screen potentials
should be reasonably close to
the values on the circuit
diagram.
The
plate
and grid potentials
will
depend on the settine
of the ZERO control,
However if it is
possible to swing the voltage through the correct value it may be
assumed that the stage is working.
Proceed in this manner until
the point is found where the voltage cannot be swung through the
value marked on the diagram.
At this point it will
be
relatively
easy to find the fault.
First check the tube involved and then
check the components.
og6m
6-1
Advertisement
Table of Contents
