Rf Troubleshooting; Introduction To Rf Troubleshooting - Nokia RM-12 Troubleshooting Instructions

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CCS Technical Documentation

RF Troubleshooting

Measurements should be done using Spectrum analyzer with high-frequency high-impedance

passive probe (LO-/reference frequencies and RF power levels) and Oscilloscope with a 10:1

probe (DC-voltages and low frequency signals).

The RF-section is build around one RF-ASIC (HELGO N7300). For easier troubleshooting, this

RF troubleshooting document is divided into sections.

Before changing HELGO, please check the following things: supply voltages are OK and serial

communication coming from baseband to HELGO.

Please note that the grounding of the PA module is directly below PA-module so it is difficult to

check or change. Most RF semiconductors are static discharge sensitive! So ESD protec-

tion must be taken care of during repair (ground straps and ESD soldering irons). HELGO and

PA are moisture sensitive so parts must be pre-baked prior to soldering.

Apart from key components described in this document, here are a lot of discrete components

(resistors, inductors and capacitors) the troubleshooting of which is done by checking if solder-

ing of the component is done properly (for factory repairs checking if it is missing from PWB).

Capacitor can be checked for shortening and resistors for value by means of an ohmmeter, but

be aware that in-circuit measurements should be evaluated carefully.

Please be also aware that all measured voltages or RF levels in this document are rough fig-

ures. Especially RF levels vary due to different measuring equipment or different grounding of

the used probe. When using RF probe, usually a good way is to use metallic tweezers to con-

nect probe ground to PWB ground as close to measurement point as possible.

Note! If the measurement values of RM-12 are as mentioned in this RF troubleshooting guide, but

there are still difficulties making calls with the device, then check the antenna contacts in PWB.

COMPANY CONFIDENTIAL

RM-12

Issue 1 11/2004

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