Tektronix Type 130, Instruction Manual

Page: 23 / 53

Maintenance — Type 130
AA
5-3
9. 0-30 Range, ADJ. 4, R98
Set the S-30 to 30
μμ
f and the L-C Meter to 30
μμ
f. Set
the ADJ. 5 control (see Figure 5-4) so that the indicating me-
ter reads full scale.
10. 0-100 Range, ADJ. 4, R97
Set the S-30 to 100
μμ
f and the L-C Meter to 100
μμ
f. Set
the ADJ. 5 control (see Figure 5-4) so that the indicating me-
ter reads full scale.
11. Zero Control Span, C2
Remove the S-30 and UHF coupling from the L-C Meter.
Set the COARSE ZERO and FINE ZERO controls so that
they are fully meshed. Check behind the panel to be pos -
itive that the meshing is absolutely completed. Set the
RANGE SELECTOR to the 10
μμ
f position and adjust C2,
(see Figure 5-3) so the meter reads 7.5.
Check whether the meter can be made to read zero with a
small rotation to the left of the COARSE ZERO control.
12. Check the accuracy of the Guard Voltage
With no external devices or leads connected to the UN-
KNOWN connector, set the RANGE SELECTOR to the 3
μμ
f
range.
Adjust the ZERO control so the meter reads at mid
scale of 1.5
μμ
f.
Now touch the centre of the UNKNOWN connector with
the tip of the finger and note which way the meter deflects.
Next, hold a 100
μμ
f, ±5% capacitor in a pair of plastic
tongs or other insulator, so as to avoid body capacity effects,
touching one lead to the centre of the UNKNOWN connector,
and the other lead to the GUARD VOLTAGE terminal. If the
meter deflects in the same direction as when touched with the
finger, GUARD VOLTAGE is low.
The deflection should be less than ½
μμ
f. If out
of tolerance, try changing V110. If this does not correct
it, change R112 to 2.7 or 3.3 meg. To bring it in. If the
meter deflects in the opposite direction as when touched
with the finger, teh guard voltage is high, however, the
meter deflection tolerance on the high side is + 1
μμ
f.