Nokia RM-154, 6275, 6275i Vari Antenna Description and Troubleshooting

Nokia Customer Care

6275/6275i (RM-154)

Mobile Terminals

Antenna Description and

Troubleshooting

Issue 1 - September 2006 Company Confidential

6275/6275i (RM-154)
Antenna Description and Troubleshooting Nokia Customer Care

Contents Page

Introduction ..................................................................................................................................................... 3

CDMA Antenna on the E-Cover Assembly............................................................................................... 4

Damaged CDMA Radiator Bezel Assembly ...........................................................................................4

Missing or Damaged CDMA Antenna and IHF Pogo Pins ................................................................4

IHF Module ....................................................................................................................................................5

Obstructed RF Feed and Ground Pads ...................................................................................................5

Damaged RF Connector .............................................................................................................................5

Auxiliary Antennas: GPS, BT, and FM ....................................................................................................... 8

GPS Antenna .................................................................................................................................................8

Bluetooth Antenna ......................................................................................................................................9

FM Antenna ...................................................................................................................................................9

Circuit Diagrams and Chip Locations ..................................................................................................10

SAR Reduction Foil...................................................................................................................................... 13

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Nokia Customer Care Antenna Description and Troubleshooting

Introduction

This troubleshooting guide addresses potential failures that affect antenna performance
of the 6275/6275i mobile terminals and discusses methods for correction of these
failures. Following are the three serviceable antennas used in the 6275/6275i mobile
terminals:

• CDMA antenna (on the E-cover assembly)

• GPS antenna (on the antenna module)

• Bluetooth antenna (on the D-cover assembly)

The following sections describe these antennas and their connections to the mobile
terminal components.

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6275/6275i (RM-154)
Antenna Description and Troubleshooting Nokia Customer Care

CDMA Antenna on the E-Cover Assembly

The E-cover (or antenna cover assembly) is comprised of the E-cover plastic part, the
CDMA antenna (or CDMA radiator) and the bezel assembly. The bezel assembly includes
the camera, flash windows, and the bezel.

The E-cover connects to the D-cover assembly via six tabs located on the four corners
and top edge of the E-cover, as well as a snap-in feature located on the bottom two
corners.

Antenna pogo pins

Ground pin

Feed pin

Figure 1: CDMA antenna on the E-cover

Damaged CDMA Radiator Bezel Assembly

The CDMA flex radiator antenna and bezel assembly are glued to the inside surface of
the E-cover. To remove the E-cover assembly from the D-cover, use the SRT-6 opening
tool to release the two snap-in tabs that secure the E-cover to the D-cover.

If either the CDMA radiator or bezel assembly is damaged, replace the E-cover assembly.

Note: You cannot replace the CDMA radiator or the bezel individually. You must
replace the entire E-cover assembly.

E-cover assembly

To reattach the E-cover assembly to the D-cover, align the E-cover above the D-cover
and apply a vertical force to engage the snap-in feature.

Missing or Damaged CDMA Antenna and IHF Pogo Pins

The CDMA antenna is connected to the PWB through two pogo pins. The CDMA antenna
pogo pins are housed in the D-cover (see Figure 1 on page 4).

If a CDMA antenna pogo pin is damaged or missing, replace the D-cover. An improper
connection between the CDMA antenna and the PWB due to a damaged or missing pogo
pin degrades the CDMA antenna performance by 5dB to more than 15dB.

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Nokia Customer Care Antenna Description and Troubleshooting

IHF Module

The IHF module impacts the CDMA antenna performance. If there is any damage to the
IHF module, replace the acoustic module.

GPS Antenna
Flex Strip on
side of IHF

Figure 2: IHF module

Obstructed RF Feed and Ground Pads

The CDMA antenna ground and feed pogo pins touch the PWB on ground and feed pads.

• If the main antenna feed pad is obstructed, removed, or covered, the CDMA
antenna feed pogo pin does not touch the PWB and the antenna gain degrades
by more than 15 dB.

• If the CDMA antenna ground pad is obstructed, removed, or covered, the ground
pogo pin does not touch the PWB and the antenna gain degrades by more than
5dB.

• If corrosion is present or the pads are missing, replace the PWB.

• If either pad is obstructed or covered, clear or clean the pads.

• If the CDMA antenna matching network is missing or damaged, replace the
component.

• If the PWB is permanently damaged, replace the PWB.

Damaged RF Connector

The CDMA RF connector could fail by not connecting the RF input to the RF output of
the RF connector. If this happens, the antenna gain degrades by about 15dB. You can
check this by testing for DC conductivity between the RF connector’s RF input and
output.

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6275/6275i (RM-154)
Antenna Description and Troubleshooting Nokia Customer Care

Perform the DC conductivity test without a cable attached to the RF connector. Because
the RF connector is also a switch, the RF output disconnects from the RF input when a
cable is inserted into the RF connector. When a cable is not inserted, the RF input is
connected to the RF output of RF connector.

• CDMA RF input – connects to the duplexer

• CDMA RF output – connects to the antenna pad through vias

• RF connector – connects to a coaxial cable

If the RF input is not connected properly to the RF output, replace the RF connector.

CDMA antenna
matching network

Feed pad

Ground pad

Flash pogo pins

RF connector

GPS pogo pins

Figure 3: Main PWB - bottom side

RF connector

Figure 4: Main PWB - top side

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Nokia Customer Care Antenna Description and Troubleshooting

Figure 5: CDMA antenna matching network schematics

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6275/6275i (RM-154)
Antenna Description and Troubleshooting Nokia Customer Care

Auxiliary Antennas: GPS, BT, and FM

See the Disassembly chapter for instructions about disassembling the mobile terminal for
auxiliary antenna troubleshooting.

GPS Antenna

The GPS antenna is a printed trace on a flex that adheres to the plastic audio module.
The GPS antenna connects to two pogo pins that are soldered to the PWB. The GPS flex
wraps around the side of the plastic audio module and ends near the audio port at the
top end of the module. Use an RF connector to test the GPS RF components directly.

Use the SRT-6 opening
tool to remove the audio

Earpiece contact pins

IHF contact pins

module at these locations

Figure 6: Remove the audio module from the D-cover

The GPS antenna system has the following possible failure modes:

• If the solder bridge of the two GPS pogo-pin pads are dirty, remove and clean the
bridge.

• If the GPS SMD pogo pins are misaligned, properly align and solder them.

• If the GPS SMD pogo pins do not operate freely or easily in their sleeves, replace
them.

• If the wrong pogo pins are soldered at the GPS SMD pogo-pin location, use the
proper GPS pogo pins.

Note that the Flash pogo pins are 5.5mm high, while the GPS SMD pogo pins
are 3.8mm high. (See Figure 3 on page 6.)

• If the GPS SMD pogo pins are improperly soldered to their pads (e.g., cold solder
joint, cracked solder joint, insufficient solder, excessive solder causing tilting),
properly align and solder them.

• If the GPS flex antenna (see Figure 2 on page 5) shows damage to the pogo-pin
pad (pressure tearing, hole, cracking, corrosion, bubbles, etc.) replace the GPS/
audio module.

• If the GPS flex antenna shows damage to the flex (e.g., tearing, cracking,
corrosion, bubble, etc.), replace the GPS/audio module.

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Nokia Customer Care Antenna Description and Troubleshooting

• If the GPS flex antenna shows damage to the audio outer gasket or screen (e.g.,
permanently creased, indented, torn, dislodged, distorted, or pressed to the side,
abnormal shape, texture, coloration), replace the GPS/audio module.

• If the GPS flex antenna trace shows damage or contamination (e.g., cracking,
discoloration, corrosion, bubble.), replace the GPS/audio module.

• If the GPS cellular RF connector is defective, replace the RF connector and make
sure the orientation is correct.

Bluetooth Antenna

The bluetooth (BT) antenna is a stamped metal sheet formed with one spring contact and
heat-staked ultrasonically to the D-cover.

Figure 7: Bluetooth antenna

A 0.5pf shunt capacitor was used for antenna impedance matching on the main PWB.

Figure 8: Bluetooth matching component on the main PWB

The BT antenna system has following possible failure modes:

• If the BT antenna spring clip is deformed, replace the D-cover.

• If the BT antenna plastic heat stakes do not hold the metal antenna firmly,
replace the D-cover.

• If the D-cover is deformed or broken, replace the D-cover.

• If the antenna match component is broken, replace the match component.

FM Antenna

The FM-antenna uses the connection through the universal headset jack (UHJ) or the
Pop-port connector to a headset to create an FM antenna of reasonable gain. If the FM
antenna is not working, the chips, UHJ connector, or the Pop-port connector could be
bad.

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6275/6275i (RM-154)
Antenna Description and Troubleshooting Nokia Customer Care

The FM antenna system has following possible failure modes:

• If the chip components are bad, replace them.

• If the UHJ or Pop-port connector is bad, replace connector.

• If the headset is bad, replace it.

Circuit Diagrams and Chip Locations

Figure 9: Matching chips for the UHJ on the audio schematic

Figure 10: Matching chips for the UHJ on the top PWB component layout

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Nokia Customer Care Antenna Description and Troubleshooting

Figure 11: Matching chips for the Pop-port connector on the system connector schematic

Figure 12: Matching chips for the Pop-port connector on the top PWB component layout

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6275/6275i (RM-154)
Antenna Description and Troubleshooting Nokia Customer Care

Figure 13: Bluetooth matching chips on the bottom PWB component layout

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Nokia Customer Care Antenna Description and Troubleshooting

SAR Reduction Foil

The SAR reduction feature uses three A-cover grounds through three clips on the
C-cover. A-cover grounding impacts the radiation performance of the mobile terminal.

If the clips of C-cover are not touching the PWB or A cover, are corroded, or are
obstructed, replace the C-cover.

Figure 14: SAR reduction A-cover (left) and C-cover (right) grounding clip locations

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Antenna Description and Troubleshooting Nokia Customer Care

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