4.2.2 ADJUSTMENT OF DETECTOR SENSITIVITY
I The detector sensitivity maybe adjusted bymeans of variable resistor
I Rv6, situated at the bottom of the right-hand printed board. The slider of
RV6 will have been cemented with some vinyllacquer; this must be softened
with a suitable solvent, such as acetone, before attempting to reposition it.
The optimurn detector sensitivity is obtained when an input of approx-
imately 100 !LV at l kc/s produces full scale deflectionon the meter with the
SENSITIVITY control fully clockwise. Apply the 100 !LV signal between the
DET +VE and -VE (chassis) terminals with the FUNCTION switch set to C
or L. lnsert an open circuit jack plug into the EXT A. C. socket to switch
off the internal oscillator; alBo check that the internal 9 V battery does not
require replacing.
4.2.3 OSCILLATOR FREQUENCY
The oscillator frequency may be adjusted by padding the value of Cl,
which is the largest capacitor mounted between the upper tag strips on the
left-hand side of the instrurnent.
4.2.4 RANGE RESISTOR R13
R13 is a loop of resistance wire soldered between two contact tags of
the RANGE MULTIPLIER switch, SE. lf one end of this wire becomes
detached it will be necessary to adjust its length to give the correct value
when soldered back into piace.
For this adjustment set the bridge to measure l a on a.c. and connect
a 10 :1:0.5"/0 resistor to the test terminals. Adjusf; R13 for balance within
1%. The wire should be left in the form of a hairpin to minimize its
inductance.
I
32
To Next Page