Case 3: Rf Internal Loopback Failure; Maintenance Step 1-Self Test - Nokia RM-761 Service Manual

RM-761; RM-799; RM-800
RF Troubleshooting
Debug and troubleshooting should be performed in the area of the Self-test failure i.e. if it is the X-tal self-
test that fails then do the X-Tal troubleshooting etc. After the troubleshooting i.e. finding and replacing the
failing components(s) the next step is to re-tune (calibrate) and do RF verification (Maintenance step 3). This
is done in order to secure that all failures have been removed and no further failures are present. The MS
passes needs to pass all RF related test. Finally the MS is assembled in Maintenance step 4 and verified in
normal mode.

Case 3: RF Internal Loopback failure

Below is the working flow described in the case where the phone fails at RF internal loop back self-test in
the Maintenance step 1.
The Internal Loop Back Self-test is a special test mode where the TX part of the X-GOLD213 is configured to
transmit on a RX frequency. This signal is weak amplified in the PA of the FEM and by the antenna switch of
the FEM directed to the RX port (not the antenna port as normal operation!) and then looped back to the RX
input of the X-GOLD213. The receiver of the X-GOLD213 is then able to measure how much of the transmitted
output power is looped back.
Since a fail in the RF loopback test can be a failure in the TX or RX (LB or HB) and the RF internal loopback self-
test is not able to highlight this, it is recommended to do a verification step in the maintenance step 3 – with
the only purpose to get the info if the failure is in the TX or RX path.
After troubleshooting i.e. finding and replacing the failing components(s) the next step is to re-tune
(calibrate) and do RF verification (Maintenance step 3). This is done in order to secure that all failures have
been removed and no further failures are present. The MS passes needs to pass all RF related test. Finally the
MS is assembled in Maintenance step 4 and verified in normal mode.
Maintenance step 1—Self test
Maintenance step 1 — Self test
Run all self-tests in order to clarify if the Self-Test can detect any failures.
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