Tait TP9100 Service Manual

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256 Receiver Fault Finding TP9100 Service Manual© Tait Electronics Limited May 2005Task 5 óCheck Biasingof IF AmplifierIf the lock status is normal, check the biasing of the IF amplifier.1. Remove the IF IQ BOT can.2. Check all components around Q404 of the IF amplifier(see Figure 11.1).3. Check the 3V supply voltage at L419; use the measurement pointshown in Figure 11.1.4. Also check the amplifier bias conditions. First measure V c betweenthe collector of Q404 and ground (see Figure 11.1).5. Secondly, check Ic. To do so, unsolder and raise one terminal of L419(tombstone position) (see Figure 11.1), connect a multimeterbetween this terminal and the pad for the terminal, and measure thecurrent.6. If the checks in Step 2 to Step 5 reveal no fault, go to Task 6.If there is a fault, repair it and go to Step 7.7. Recalibrate the receiver using the calibration application.8. Confirm the removal of the fault and go to “Final Tasks” onpage 134. If the repair failed, go to Task 7.V c : 2.0±0.2VI c: 1.8±0.5mA