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page 26 Document no. 93-005-35-C5
Table 9 Troubleshooting the Receiver
Problem Possible Cause
1. Lack of RF signal
present at Receiver,
yet optical power is
functioning.
If a spectrum analyzer or power meter
is not available then use a DVM and
adjust the gain control for RF signal
strength (RSSI) so that the reading is
> 0.2VDC. (See
Table 5 7870R Receiver
Pinout
on page21).
Conclusion: If signal still not present
then transmitter input stage amplifier
or receiver amplifier is defective.
Contact factory.
2. No optical power,
LED not
illuminated.
a. Transmitter is not functioning, see
above.
b. There is a break or severe bend in
the fiber optic cable. Use an optical
power meter or another
functioning receiver unit to verify
optical power coming down the
fiber.
c. The connector is dirty. Clean it.
d. Optical power too low, too many
splits, too long a distance (thus
exceeding optical budget). System
may still function without LED
illuminated although at reduced
performance.
3. Optical power light
illuminated with
disconnected optical
input.
Damaged (leaky) photodiode. Unit
may still function, otherwise contact
Factory for service.
4. The RF LED is not
illuminated.
Verify that the RF signal strength
(RSSI) is <0.2° VDC.