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Detector Options Narrowband Internal
MEAS1
5
at a time. Inputs B and R should be
at at about 0 dB. Input A should look somewhat similar
to the re
ection trace in Figure 4-4 (Figure 4-5 for HP 8713C/14C). If any of these fail, and
assuming the source board is functioning properly, then the receiver is probably bad; replace
the receiver. For the HP 8713C/14C, refer to the rst paragraph in this section.
Now press
Detector Options Broadband Internal
MEAS1
5
should be a fairly
at line at 0 dB. B* should be within
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. hese 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
You must perform this procedure
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. his 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 a ected much and should still show a
at line at 0 dB if the RF
OU 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 8711C/12C/30A, but you
must be experienced in replacing surface mount components. Replacing these diodes in the
HP 8713C/14C is much more dicult. he 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 on the HP 8713C/14C unless the procedure is performed by a
quali ed technician who is very pro cient with small surface mount components and all the
proper equipment is available.
For the HP 8711C/12C/30A:
Detector diodes CR1, CR2 (HP part number 1900-0262)
Protection diodes CR36, CR37 (HP part number 1900-0096)
For the HP 8713C/14C:
Detector diodes CR53, CR54 (HP part number 1900-0293)
Protection diodes CR45, CR46, CR47, and CR48 (HP part number 1900-0273)
When replacing the detector diodes, note the polarity of the existing parts and make sure
the new ones are oriented the same! See Figure 4-6 (for HP 8711C/12C/30A) or Figure 4-7
(for HP 8713C/14C) for component location. You will have to remove the receiver shield to
access these parts. On the HP 8713C/14C, CR47 and CR48 are mounted in the same location as
CR45 and CR46, but on the opposite (top) side of the board. All adjustments listed for the A5
receiver assembly replacement should be performed after replacing the diodes. See able 3-1,
\Post Repair Procedures."
and select inputs
and select inputs R* and B*. R*
6
3 dB of a
at line at 0 dB. If any of
only
at a static-safe workstation to prevent
T roubleshoot ng and Block D agrams
,
and
one
A
B
R
4-21
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