Model 4342A
Section V
Paragraphs 5-37 to 5-44
5-37. TROUBLESHOOTING GUIDES. deflection caused by such external electro-
magnetic field is irrespective of the Q range.
5-38. This paragraph and those below provide One solution to this trouble is to enclose
information helpful to isolating a faulty the instrument in a grounded wire net shield.
circuit in a defective unit and the appro- Securely ground the instrument.
priate remedy for the trouble. Component
level troubleshooting procedures are provided 5-41. Operation in High Humidity
in Figures 5-13 and 5-14 in the form of flow Environment.
diagrams [however, for simple circuits com-
posed of only a few (active) components, The Q factor of a high Q inductor is generally
these figures treat the breakdown only to sensitive to atmospheric humidity. Usually,
circuit block level and component level ordinary high Q inductors tend to show a pro-
troubleshooting procedure is omitted]. Before nounced decrease in Q factor when they are
proceeding with troubleshooting, verify located in a high humidity environment (more
whether any external factor relating to the than 80%). If Q meter indicates a lower Q
instrument operating environment is contri- value (different from a nominal value of the
buting to the trouble symptoms. The follow- sample), compare instrument reading by using
ing paragraphs outline some considerations a Q reference coil or a stable inductor (her-
for such external troubles: metically sealed).
5-39. High Frequency Line Noise. 5-42. ELEMENTARY TROUBLESHOOTING GUIDE.
High frequency noise superposed on the AC 5-43. Meter Zeroing Troubles.
power line may possibily cause an abnormal
deflection of the Q meter regardless of the If Q meter does not indicate zero after the
sample measured. If meter pointer shows al- instrument is turned on and if meter zero
most the sane deflection on any FREQUENCY and adjustment (Figure 3-6) is not successful,
Q RANGE setting, check quality of operating A6 DC Amplifier Assembly is probably faulty.
power line. To isolate trouble, proceed as Check differential meter amplifier (A6Q2, 43,
follows: 44 and QS) and dc power supply voltages on
the circuit board.
1) Operate the instrument from another ac
power line and attempt measurement. 5-44. Incorrect Q Meter Indication.
2) Securely ground the instrument chassis If indicated Q values of Q measurements are
to earth. incorrect (compared with a known sample),
the trouble is probably located in either
If the symnton disappears or is different, the oscillator section or the Q voltmeter
use the sane procedures on actual neasure- section. (If no deflection at all can be
ments or use a line filter in the power line. obtained, first check power supply voltages).
To isolate the trouble, proceed as follows:
5-40. Operating in a Strong Electromagnetic
Field. a. Connect a RF Voltmeter to 4342A LO
and GND terminals.
When the instrument is operated in a strong
RF electromagnetic field, two (or more) re- b. Set 4342A Q RANGE to 30.
sonant frequency points are sometimes ob-
served on the Q meter indication. This C. Rotate FREQUENCY dial from lowest to
symptom arises from the fact that the Q- highest frequency on each FREQUENCY
measuring circuit resonates with the oscil- RANGE setting and check RF voltmeter
lator signal injected into the circuit and reading.
additionally with the RF signal induced by
the electromagnetic field as well. In prac- d. RF Voltmeter reading should be within
tice, this trouble sometimes occurs when the 30nV *O.SmVrns at any frequency set-
instrument is located near a high power ting. If this check fails, trouble-
transmitting station (such as a broadcasting shoot oscillator section and follow
station). The meter "true" tuning deflection Figure 5-12 Troubleshooting Tree. If
can be easily distinguished from the "false" OK, troubleshoot voltmeter section and
behavior because the amplitude of any meter follow Figure 5-13 Troubleshooting
Tree.
5-18 |
ACEC
