Status Indicator And Touch Key Backlight Circuits - Huawei U8655N Maintenance Manual

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U8655

Maintenance Manual

Troubleshooting Key Failure

9.4.6 Status Indicator and Touch Key Backlight Circuits

The U8655N's status indicator (tricolor indicator) provides red, green and blue light sources

that are driven by the PM8029's three LED drivers.

Light

Source

Red

Green

Blue

The KYPD_DRV_N (PM8029) is used to adjust the brightness of the keypad's backlight, and

VPH_PWR is used to supply power to the backlight LEDs. The keypad backlight is provided

by two white LEDs. The light from the LEDs are transmitted to the key area using a light

guide film.

Issue 1.0 (2012-02-23)

Key failure

Is the keypad on the

FPC in good contact

with the dome sheet?

Are the FPC and ZIF

connector connected

properly?

Return the phone

to the factory

Driver Pin (PM8029)

LED_RED_DRV_N (MPP3)

LED_GREEN_DRV_N (MPP5)

LED_BLUE_DRV_N (MPP8)

Huawei Proprietary and Confidential

9 Principles and Failure Analysis

Clean the

keypad and the

dome sheet

Re-connect them

Description

Adjusted using electric current

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