Introduction
Full teardown of a cordless phone and accessories from 2001.
What you need
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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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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.
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The shield took about 20 minutes to remove with diagonal cutters, 2 pairs of pliers, and 3 metal spudgers.
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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:
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Toshiba TB31261AF cordless telephone RF chip
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Ceramic resonators
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Unidentified square ceramic components with 2 cylindrical holes in them horizontally (anyone who has an idea what they are, please comment.)
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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.
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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
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Phone is held together with only phillips screws.
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Battery, the most likely part to fail, is a standard component and is easily replaceable.
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Case is difficult to open.
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Wireless module is very hard to replace and impossible to repair.
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All wires (except for the battery) are soldered to the circuit board instead of using connectors.
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Components on the main board:
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4 MHz crystal
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Variable capacitor
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Small audio transformer
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Miniature fuse
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Varistor for surge protection
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This board was manufactured on September 3, 2001.
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Repairability Score: 4/10
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Secondary base station is assembled with only phillips screws.
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Circuit boards use mainly through-hole parts, so repair of individual components is easier.
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Case requires lots of spudgering to open.
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Removing the board requires a long screwdriver.
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Wireless module is very hard to replace and impossible to repair.
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All wires and ribbon cables are soldered to the board and reinforced with hot glue.
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So what is inside the mysterious metal box?
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Samsung K9F4008W0A-TCB0 512x8 Kb (512 KB) flash memory (designed for digital audio recording)
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Crystal oscillator, covered in the same unusual substance found on the main board.
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Unknown IC D16529CAC11CQC. Googling it turns up nothing that makes any sense.
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This board is probably where the messages are stored.
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Repairability Score: 3/10
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Base station is only held together with phillips screws.
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Circuit boards use mainly through-hole parts, so repair of individual components is easier.
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Removing the top circuit board is difficult because the buttons are attached to the top case with clips.
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Opening the case requires 2 metal spudgers and a lot of force.
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Removing the bottom circuit board is difficult because the case is still attached with soldered ribbon cables.
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Wireless module is very hard to replace and impossible to repair.
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All wires and ribbon cables are soldered to the board and reinforced with hot glue.
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Overall repairability score: 5/10
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The handset battery, the most likely part to fail, is a standard component and is easily replaceable.
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Circuit boards use mainly through-hole parts, so repair of individual components is easier.
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Entire phone is held together with phillips screws
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Cases are difficult to open and require heavy spudgering.
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Most parts were not designed to be repaired.
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All wires and ribbon cables are soldered to the board and reinforced with hot glue.
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