Introduction

Full teardown of a cordless phone and accessories from 2001.

This teardown is not a repair guide. To repair your GE 27990G3 Cordless Phone, use our service manual.

This is a teardown of a GE 27990G3 cordless phone system from 2001. Sadly, while it still works, its 2.4 GHz wireless transmitter interferes with WiFi. This is a teardown of a GE 27990G3 cordless phone system from 2001. Sadly, while it still works, its 2.4 GHz wireless transmitter interferes with WiFi. This is a teardown of a GE 27990G3 cordless phone system from 2001. Sadly, while it still works, its 2.4 GHz wireless transmitter interferes with WiFi.
  • This is a teardown of a GE 27990G3 cordless phone system from 2001. Sadly, while it still works, its 2.4 GHz wireless transmitter interferes with WiFi.

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Part I: The Handset. Remove the battery door on the back. Remove the battery door on the back.
  • Part I: The Handset.

  • Remove the battery door on the back.

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Use needlenose pliers to disconnect the battery connector. The battery is a 3.6V Nickel-Cadmium rechargeable battery made up of 3 AAA-sized cells The battery is a 3.6V Nickel-Cadmium rechargeable battery made up of 3 AAA-sized cells
  • Use needlenose pliers to disconnect the battery connector.

  • The battery is a 3.6V Nickel-Cadmium rechargeable battery made up of 3 AAA-sized cells

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Remove 2 phillips screws inside the battery compartment.
  • Remove 2 phillips screws inside the battery compartment.

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After some aggressive spudgering (the pictures make it look much easier), the back of the case can be removed. After some aggressive spudgering (the pictures make it look much easier), the back of the case can be removed. After some aggressive spudgering (the pictures make it look much easier), the back of the case can be removed.
  • After some aggressive spudgering (the pictures make it look much easier), the back of the case can be removed.

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The charging contacts can now be easily removed.
  • The charging contacts can now be easily removed.

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Remove 2 screws on what appears to be the wireless board. Remove 2 screws on what appears to be the wireless board.
  • Remove 2 screws on what appears to be the wireless board.

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The wireless board can be flipped up, but is still attached to the main board by a short ribbon cable. Remove 2 screws on the main board. Remove 2 screws on the speaker.
  • The wireless board can be flipped up, but is still attached to the main board by a short ribbon cable.

  • Remove 2 screws on the main board.

  • Remove 2 screws on the speaker.

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The mainboard assembly can now be removed from the front case. The mainboard assembly can now be removed from the front case.
  • The mainboard assembly can now be removed from the front case.

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The wireless board is attached by a soldered and hot-glued in ribbon cable, which must be cut off to remove. The wireless board is attached by a soldered and hot-glued in ribbon cable, which must be cut off to remove.
  • The wireless board is attached by a soldered and hot-glued in ribbon cable, which must be cut off to remove.

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Components on the main board: Speaker
  • Components on the main board:

    • Speaker

    • Message indicator LED

    • Ringer switch

    • Electret microphone

    • Unknown potted 'Blob' IC

    • Piezo buzzer for ringer

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Whoever designed the wireless module really didn't want anyone to know what was inside. The very thick EMI shield is soldered, crimped, and epoxied on. The shield took about 20 minutes to remove with diagonal cutters, 2 pairs of pliers, and 3 metal spudgers. Needless to say, the shield is irreversibly damaged and the wireless module will probably never work again.
  • Whoever designed the wireless module really didn't want anyone to know what was inside. The very thick EMI shield is soldered, crimped, and epoxied on.

  • The shield took about 20 minutes to remove with diagonal cutters, 2 pairs of pliers, and 3 metal spudgers.

  • Needless to say, the shield is irreversibly damaged and the wireless module will probably never work again.

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Components inside the wireless module: Toshiba TB31261AF cordless telephone RF chip
  • Components inside the wireless module:

    • Toshiba TB31261AF cordless telephone RF chip

    • Ceramic resonators

    • Unidentified square ceramic components with 2 cylindrical holes in them horizontally (anyone who has an idea what they are, please comment.)

  • The back of the board says that it was manufactured on August 29, 2001, making the phone 14 years old at the time of writing.

  • Interestingly, the Toshiba TB31261AF is designed for a 900MHz cordless telephone, but this is a 2.4GHz model.

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Repairability score: 6/10 Phone is held together with only phillips screws.
  • Repairability score: 6/10

  • Phone is held together with only phillips screws.

  • Battery, the most likely part to fail, is a standard component and is easily replaceable.

  • Case is difficult to open.

  • Wireless module is very hard to replace and impossible to repair.

  • All wires (except for the battery) are soldered to the circuit board instead of using connectors.

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Part II: The Secondary Base Station Remove 2 phillips screws on the bottom.
  • Part II: The Secondary Base Station

  • Remove 2 phillips screws on the bottom.

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The top case can be removed with some spudgering. The top case can be removed with some spudgering. The top case can be removed with some spudgering.
  • The top case can be removed with some spudgering.

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Remove 1 screw to remove the wireless module. Remove 1 screw to remove the wireless module. Remove 1 screw to remove the wireless module.
  • Remove 1 screw to remove the wireless module.

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Just like in the handset, the wireless module is connected to the main board with a soldered ribbon cable. I'm sensing a theme here. Remove 2 screws that hold down the main board. Remove 2 screws that hold down the main board.
  • Just like in the handset, the wireless module is connected to the main board with a soldered ribbon cable. I'm sensing a theme here.

  • Remove 2 screws that hold down the main board.

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The main circuit board can be removed from the bottom case. Remove 4 screws holding in the button board and charging contacts from the top case. Remove 4 screws holding in the button board and charging contacts from the top case.
  • The main circuit board can be removed from the bottom case.

  • Remove 4 screws holding in the button board and charging contacts from the top case.

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The wireless module can be cut away from the logic board. This wireless module is identical to the one in the handset except for the fact that it used coiled wires instead of straight wires for antennas. This wireless module is identical to the one in the handset except for the fact that it used coiled wires instead of straight wires for antennas.
  • The wireless module can be cut away from the logic board.

  • This wireless module is identical to the one in the handset except for the fact that it used coiled wires instead of straight wires for antennas.

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Remove 2 screws to remove the support for the wireless module. The plastic pieces used to hold down the board can also be removed.
  • Remove 2 screws to remove the support for the wireless module.

  • The plastic pieces used to hold down the board can also be removed.

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The button board contains a lonely button, 2 LEDs, and is connected with a soldered ribbon cable reinforced with hot glue.
  • The button board contains a lonely button, 2 LEDs, and is connected with a soldered ribbon cable reinforced with hot glue.

  • This board appears to have been manufactured on April 17, 2001.

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Components on the main board: 4 MHz crystal
  • Components on the main board:

    • 4 MHz crystal

    • Reed relay

    • Variable capacitor

    • Small audio transformer

    • Miniature fuse

    • Varistor for surge protection

  • This board was manufactured on September 3, 2001.

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Repairability Score: 4/10 Secondary base station is assembled with only phillips screws.
  • Repairability Score: 4/10

    • Secondary base station is assembled with only phillips screws.

    • Circuit boards use mainly through-hole parts, so repair of individual components is easier.

    • Case requires lots of spudgering to open.

    • Removing the board requires a long screwdriver.

    • Wireless module is very hard to replace and impossible to repair.

    • All wires and ribbon cables are soldered to the board and reinforced with hot glue.

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Part III: The Main Base Station First step: remove 4 screws. First step: remove 4 screws.
  • Part III: The Main Base Station

  • First step: remove 4 screws.

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The case for the main base station can be opened, but it requires 2 spudgers and much more force than the other one. Remember how I said soldered ribbon cables were becoming a theme here? I was right. Remember how I said soldered ribbon cables were becoming a theme here? I was right.
  • The case for the main base station can be opened, but it requires 2 spudgers and much more force than the other one.

  • Remember how I said soldered ribbon cables were becoming a theme here? I was right.

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Remove the buttons from the side of the case. Remove the buttons from the side of the case.
  • Remove the buttons from the side of the case.

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Remove 2 screws holding down the wireless module. Remove 2 more screws holding down the plastic pieces attached to the circuit board. Remove 2 more screws holding down the plastic pieces attached to the circuit board.
  • Remove 2 screws holding down the wireless module.

  • Remove 2 more screws holding down the plastic pieces attached to the circuit board.

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Remove another 2 screws on the other side of the board. Remove the microphone from its holder.
  • Remove another 2 screws on the other side of the board.

  • Remove the microphone from its holder.

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In order to remove the board from the bottom case, you have to carefully reach in and free each one of the plastic pieces attached to the board from a clip on the bottom case. All of the cables to the main board can now be cut and the wireless module can be cut off of the main board. All of the cables to the main board can now be cut and the wireless module can be cut off of the main board.
  • In order to remove the board from the bottom case, you have to carefully reach in and free each one of the plastic pieces attached to the board from a clip on the bottom case.

  • All of the cables to the main board can now be cut and the wireless module can be cut off of the main board.

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Components on the main board: LM324 Quad Operational Amplifier
  • Components on the main board:

    • LM324 Quad Operational Amplifier

    • Electret microphone

    • Small audio transformer

    • Reed relay

    • Same potted 'Blob' IC found in the handset

    • HEF4053 triple SPDT analog switch

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The main board in the base station has patches of an unknown yellowish-brown substance on it that appears to be some kind of weak adhesive, and it seems to be scattered in no obvious pattern. The main board in the base station has patches of an unknown yellowish-brown substance on it that appears to be some kind of weak adhesive, and it seems to be scattered in no obvious pattern.
  • The main board in the base station has patches of an unknown yellowish-brown substance on it that appears to be some kind of weak adhesive, and it seems to be scattered in no obvious pattern.

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Remove 2 screws to remove the charging contacts in the upper case. Remove 2 screws to remove the charging contacts in the upper case.
  • Remove 2 screws to remove the charging contacts in the upper case.

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Remove 3 screws to remove the speaker cover. This speaker cover appears to have been designed to accomodate both a low-profile speaker and a speaker with a larger magnet on the back. This speaker cover appears to have been designed to accomodate both a low-profile speaker and a speaker with a larger magnet on the back.
  • Remove 3 screws to remove the speaker cover.

  • This speaker cover appears to have been designed to accomodate both a low-profile speaker and a speaker with a larger magnet on the back.

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The upper case board can be removed by removing 5 screws. The upper case board can be removed by removing 5 screws.
  • The upper case board can be removed by removing 5 screws.

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Remove 4 screws on the mysterious metal box. Remove 4 screws on the mysterious metal box.
  • Remove 4 screws on the mysterious metal box.

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The entire top case assembly can be removed from the printer after using a spudger to free the large buttons from clips in the top case. The entire top case assembly can be removed from the printer after using a spudger to free the large buttons from clips in the top case.
  • The entire top case assembly can be removed from the printer after using a spudger to free the large buttons from clips in the top case.

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So what is inside the mysterious metal box? Samsung K9F4008W0A-TCB0 512x8 Kb (512 KB) flash memory (designed for digital audio recording) Crystal oscillator, covered in the same unusual substance found on the main board.
  • So what is inside the mysterious metal box?

    • Samsung K9F4008W0A-TCB0 512x8 Kb (512 KB) flash memory (designed for digital audio recording)

    • Crystal oscillator, covered in the same unusual substance found on the main board.

    • Unknown IC D16529CAC11CQC. Googling it turns up nothing that makes any sense.

    • This board is probably where the messages are stored.

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The major components on the top case board: Dual 7-segment display LM386 audio amplifier
  • The major components on the top case board:

    • Dual 7-segment display

    • LM386 audio amplifier

    • Message indicator LED

  • This board was manufactured on July 27, 2001.

  • The speaker is a standard 2" low profile 8 ohm 0.25 watt speaker.

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All of the boards in this phone system have terrible solder quality. I was able to cleanly remove the 7-segment display, about 20 capacitors, 3 voltage regulators, 1 transformer, and 2 crystal oscillators without damaging them using needle nose pliers. All of the boards in this phone system have terrible solder quality. I was able to cleanly remove the 7-segment display, about 20 capacitors, 3 voltage regulators, 1 transformer, and 2 crystal oscillators without damaging them using needle nose pliers.
  • All of the boards in this phone system have terrible solder quality. I was able to cleanly remove the 7-segment display, about 20 capacitors, 3 voltage regulators, 1 transformer, and 2 crystal oscillators without damaging them using needle nose pliers.

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Repairability Score: 3/10
  • Repairability Score: 3/10

  • Base station is only held together with phillips screws.

  • Circuit boards use mainly through-hole parts, so repair of individual components is easier.

  • Removing the top circuit board is difficult because the buttons are attached to the top case with clips.

  • Opening the case requires 2 metal spudgers and a lot of force.

  • Removing the bottom circuit board is difficult because the case is still attached with soldered ribbon cables.

  • Wireless module is very hard to replace and impossible to repair.

  • All wires and ribbon cables are soldered to the board and reinforced with hot glue.

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Overall repairability score: 5/10
  • Overall repairability score: 5/10

  • The handset battery, the most likely part to fail, is a standard component and is easily replaceable.

  • Circuit boards use mainly through-hole parts, so repair of individual components is easier.

  • Entire phone is held together with phillips screws

  • Cases are difficult to open and require heavy spudgering.

  • Most parts were not designed to be repaired.

  • All wires and ribbon cables are soldered to the board and reinforced with hot glue.

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Attached Documents

jrw01

Member since: 08/22/2013

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