HP 5334B Service Manual page 195

d. Adjust potentiometer so that pin 3 is less (more negative) than pin 2.
e. Verify that pin
1
is
-
5.OV
+
0.4V. If the voltage at pin
1
is not
-
5.OV
2
0.4V, the comparator circuit
is malfunctioning; go to step f.
f. Replace U306. After replacing U306 and a problem still exists in the Threshold Comparator circuit,
check R328 and the other components (such as R319, R318, (324, and C329) connected to U306;
they could be preventing U306 from working properly.
g. Check bias resistor R303 and ECL Buffer U301 pin 1 1 .
8-456. SIGNATURE ANALYSIS
8-457. Signature Analysis can be used to troubleshoot the 5334B. Correct signatures are defined as the signa-
tures documented in the troubleshooting procedure of the 5334B. An incorrect signature is defined as a signa-
ture displayed on the signature analyzer that does not match the documented one for the node being probed. If
the correct signatures are repeatable, then measuring an incorrect signature during troubleshooting will accurate-
ly indicate an incorrect waveform for that node. The troubleshooter can then quickly back-trace through the cir-
cuit following incorrect waveforms to the faulty node. The fault is found at the point where back-tracing further
results in correct signatures. For instance, if the signature for an output of a device is incorrect, signatures are
taken at the inputs for that device. If the input signatures are correct, then the fault has been isolated to the out-
put node. If any input signature is incorrect, back-tracing continues along that signal path.
NOTE
The signatures listed in this manual are intended to apply only to instru-
ments with serial number prefixes up to and including those called out on
the title page. Newer instruments will have a Manual Change Supplement
supplied with the manual to note differences (if any) with the published sig-
natures.
8-458. The Signature Analysis testing is designed so that the Executive and HP-IB microcomputers (MCUs)
can be tested separately from the rest of the instrument. The connection instructions are included for the two
MCUs in the following paragraphs.
HP 5334B
-
Service Manual
8-75