HP 87114B, Руководство по обслуживанию

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Figure 4-5. HP 8713B/14B Reection Measurement with Through Cable
Press 4 CHAN 1 5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
Detector Options
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
Narrowband Internal and select inputs
NNNNN
A ,
NNNNN
B and
NNNNN
R
one at a time . Inputs B and R should be at at about 0 dB . Input A should look somewhat
similar to the reection trace in Figure 4-4 (Figure 4-5 for HP 8713B/14B). Now press 4
CHAN 1
5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
Detector Options
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
Broadband Internal and select inputs R* and B*. R* should be a
fairly at line at 0 dB . B* should be within 6 3 dB of a at line at 0 dB . If any of these fail,
and assuming the source board is functioning properly , then the receiver is probably bad (see
paragraph below); replace the receiver .
If the B* input looks bad, then the B* detector diodes may be damaged. Sometimes this is
accompanied by poor input match at the RF IN port. If this is the case , it is possible to replace
these diodes separately , thus saving time and money . These diodes will generally be the rst
components to fail if the maximum input level is exceeded or if it is subjected to excessive
ESD . Refer to \A5 Receiver Diode Replacement," below .
A5 Receiver Assembly Diode Replacement
Caution
Y ou must perform this procedure only at static-safe workstation to prevent
damage from electrostatic discharge (ESD). See Figure 4-1.
If the analyzer's RF IN port is overpowered by excessive RF or by ESD , the detector diodes
may be damaged or shorted. If damaged by ESD , degradation may take place over a period of
time . This will cause bad input match causing a through-line cable to no longer appear at. In
addition, selecting internal broadband detection on B* will show low or nonexistent power .
R* should not be aected much and should still show a at line at 0 dB if the RF OUT port is
terminated in a correct load. It is also possible that the protection diodes could be damaged.
Replacing just these diodes is fairly easy in the HP 8711B/12B, but you must be experienced
in replacing surface mount components . Replacing these diodes in the HP 8713B/14B is much
more dicult. The parts are smaller , and great care must be exercised to ensure that all excess
solder and ux is removed before attaching the new diodes . Do not attempt to replace diodes
T roubleshooting and Block Diagrams 4-17