Troubleshooting Ic Opamps - Orban OPTIMOD-FM 8500S Operating Manual

5-14
TROUBLESHOOTING

Troubleshooting IC Opamps

F) In "This connection uses the following items," uncheck all except for "Internet
Protocol (TCP/IP)." You can also leave "QoS Packet Scheduler" checked if you
like.
G) In "This connection uses the following items," select "Internet Protocol
(TCP/IP)" and then click the "Properties" button.
The "Internet Protocol (TCP/IP) Properties" window opens.
H) Choose "Obtain an IP address automatically" and "Obtain DNS server address
automatically."
I) Click the "Advanced..." button on the "Internet Protocol (TCP/IP)" Window.
J) In the "Advanced TCP/IP Settings," select the "General" Tab; make sure that
no check boxes are checked.
K) Click "OK" to dismiss the "Advanced TCP/IP Settings" window.
L) Click "OK" to dismiss the window whose name is your new connection.
M) Restart your computer. (This resets the serial port and reduces the likelihood
that you will encounter problems connecting to the 8500S.)
IC opamps are operated such that the characteristics of their associated circuits are
essentially independent of IC characteristics and dependent only on external feed-
back components. The feedback forces the voltage at the (–) input terminal to be
extremely close to the voltage at the (+) input terminal. Therefore, if you measure
more than a few millivolts difference between these two terminals, the IC is proba-
bly bad.
Exceptions are opamps used without feedback (as comparators) and opamps with
outputs that have been saturated due to excessive input voltage because of a defect
in an earlier stage. However, if an opamp's (+) input is more positive than its (–) in-
put, yet the output of the IC is sitting at –14 volts, the IC is almost certainly bad.
The same holds true if the above polarities are reversed. Because the characteristics
of the 8500S's circuitry are essentially independent of IC opamp characteristics, an
opamp can usually be replaced without recalibration.
A defective opamp may appear to work, yet have extreme temperature sensitivity. If
parameters appear to drift excessively, freeze-spray may aid in diagnosing the prob-
lem. Freeze-spray is also invaluable in tracking down intermittent problems. But use
it sparingly, because it can cause resistive short circuits due to moisture condensation
on cold surfaces.
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