Rx Dc Troubleshooting N750 - Nokia RM-11 Series Troubleshooting Manual

RM-11
Troubleshooting - RF

Rx DC Troubleshooting N750

Eventually, you will run into an N750 failure that has the symptoms of high current in
Local Mode with just the Rx turned on. There can be two common explanations for this:
(1) No presence of an LO signal, and (2) input impedance drop shorting out one of the DC
supply pins to the chip. IMPORTANT: YOU MUST CHECK FOR BOTH CONDITIONS BEFORE
REPLACING THE CHIP. If you have no LO signal, refer to the section of this chapter on
troubleshooting the UHF LO. If you have a significant supply voltage drop on one of the
supply pins, then change N750.
Condition (Local Mode, Set
Rx only in RF Main Mode)
Good mobile terminal
No UHF LO Signal present
Pin 13 shorted
© 2005 Nokia Corporation
Page 60
CC Technical Documentation
Supply Current (from Power Supply)
104mA
254mA
255mA
Confidential Issue 2 09/2005