Troubleshooting Procedures; Bottom Shield Removal; Servicing Etched Circuit Boards - HP 333A Technical Manual

Model 333A/334A
NOTE
Selector positions for the
selector will be referred
MIN = Position 1, next step = Position
2, etc. , to MAX = Position 6.
b. Set Distortion Analyzer controls as follows:
FUNCTION Selector . . . . . . . SET LEVEL
SENSITIVITY Selector . . . . . .Position 5
SENSITIVITY VERNIER Control . . . . . MAX
METER RANGE Selector . . . . 0.01 VOLTS
c. Set Frequency Response Test Set controls (-hp-
Model 739AR)as follows:
RANGE SELECTOR . . . . . . . . EXTERNAL
OUTPUT ATTENUATOR . . . . . . . . 0.03
d. Set Oscillator (-hp- Model 200SR) frequency to
400 cps. Adjust AMPLITUDE control for an indica-
tion on Distortion Analyzer meter of 0. 9 on the 1. 0)
scale.
e. Adjust Frequency Response Test Set METER
SET for SET LEVEL indication.
f. Change Oscillator frequency to 100 Kc. Read-
just Oscillator AMPLITUDE control for SET LEVEL
indication on Frequency Response Test Set meter.
g. Adjust S2C 5 for a meter indication of O. 9 on the
1.0 scale.
h. Repeat steps d through f, calibrating sensitivity
at the settings indicated in Table 5-7.
NOTE
When switching the SENSITIVITY selector,
be careful not to move SENSITIVITY VERN-
IER control from MAX position.
Table 5-7. Sensitivity Switch Calibration
SENSITIVITY Test Set
Switch ATTENUATOR
I
I
Position 5
Position 4
Position 3
Position 2
Position 1

5-33. TROUBLESHOOTING PROCEDURES.

5-34. This section contains procedures designed to as-
sist in the isolation of malfunctions. These procedures
are based on a systematic analysis of the instrument
circuits in an effort to localize the problem. These
operations should be undertaken only after it has been
established that the difficulty can not be eliminated by
the Adjustment and Calibration Procedures. An in-
vestigation should also be made to insure that the
trouble is not a result of conditions external to the
333A/334A.
THE 333A/334A CONTAINS VERY HIGH
IMPEDANCE, HIGH FREQUENCY CIR-
CUITS. CONTAMINATION OF THE
SWITCHES, CIRCUIT BOARDS OR TUN-
ING CAPACITORS WILL CAUSE HIGH
SENSITIVITY
to as follows:
Adjust
for 0 9
I I
0
0.03 S2C 5
0.1 S2C 4
0.3 S2C 3
1.0 S2C2
3.0 S2C 1
Paragraphs 5-33 to 5-42 and Table 5-7
IMPEDANCE LEAKAGE PATHS AND SUB-
SEQUENT DETERIORATION OF THE PER-
FORMANCE OF THE INSTRUMENT.
AVOID TOUCHING ANY OF THESE CIR-
CUITS WITH THE BARE FINGER, AS
SKIN OILS ARE EXTREMELY CONTAMI-
NATING. IF HANDLING IS NECESSARY,
WEAR CLEAN COTTON OR RUBBER
GLOVES. DO NOT USE A PENCIL TO
TRACE CIRCUITS IN THE INSTRUMENT.
GRAPHITE PENCIL LEAD IS AN EX-
TREMELY GOOD CONDUCTOR AND MN
ACCIDENTLY INTRODUCED PATH OF
THIS TYPE IS SOMETIMES DIFFICULT
TO LOCATE. TO AVOID SURFACE CON-
TAMINATION OF A PRINTED CIRCUIT
OR SWITCH, CLEAN WITH A WEAK SO-
LUTION OF WARM WATER AND MILD DE-
TERGENT AFTER REPAIR. RINSE THOR-
OUGHLY WITH CLEAN WATER AND
ALLOW IT TO DRY COMPLETELY BE-
FORE OPERATING. DO NOT USE ALCO-
HOL OR ANY OTHER CLEANING SOLU-
TION EXCEPT DETERGENT AND WATER.
DO NOT APPLY ANY COMMERCIAL
MOISTURE SEALING SPRAY TO THE
BOARDS. APPLICATION OF THESE
AGENTS WILL CAUSE LEAKAGE PATHS
AND SUBSEQUENT DETERIORATION TO
THE OPERATION OF THE INSTRUMENT.
5-35. Conduct a visual check of the 333A/334A for
possible burned or loose components, loose connec-
tions, or any other obvious condition which might
suggest a source of trouble.
5-36. Table 5-8 contains a summary of the front panel
symptoms and internal adjustment symptoms that
It should be used in initial
might be encountered.
efforts to select a starting point for troubleshooting
procedures.
5-37. Table 5-9, in conjunction with Figure 5-10, con-
tains procedures which may be used as a guide in
The steps in Table 5-9 de-
isolating malfunctions.
scribe the normal conditions which should be encoun-
tered during the checks (circled numbers N ) in
Figure 5-10.
5-38. The checks outlined in Table 5-9 are not designed
to measure all the circuit parameters, rather to local-
ize a malfunction. Therefore, it is quite possible that
additional measurements will be required to complete-
ly isolate a problem. Circuit parameters may vary
slightly between instruments; therefore, it should not
be necessary to precisely duplicate the values given.

5-39, BOTTOM SHIELD REMOVAL.

5-40. The bottom shield is attached by seven screws.
Access to six is obtained by removing the bottom
Access to the other is obtained by removing
cover.
the left (as viewed from the front of instrument) rear
side cover.

5-41. SERVICING ETCHED CIRCUIT BOARDS.

5-42. The Model 333A has six-etched circuit boards
and the Model 334A, seven. Use caution when re-
moving them to avoid damaging mounted components.
TM 11-6625-1576-15
Section V
5-11