I need yours expertise to fix this: E book reader

Discussion in 'General Electronics Chat' started by ranatungawk, Apr 21, 2012.

  1. ranatungawk

    Thread Starter Active Member

    Oct 30, 2008
    I need yours expertise to fix this

    I’m using Chinese 7’’ Ebook reader since 4 months. Yesterday I charged it and forgot to stop charging until 12 hr. after 12 hr. I removed it from the charger. Till then, it cant be turned on (no power at all, it’s dead). One or two times it came up but after 1min got down again. However, now it doen’t come up at all.

    I removed the battery and kept 1or 2hr and tried to ON, but it’s still dead. Then I check the board. I found the power section is controlled by a little chip called “PT1502” (data sheet attached herewith). According to it, as far as I could understand, when power button is pressed 3v-5v signal should come to the PT1502 in order to turn on the CPU. However, when I check, I found voltage on the above pin is around 2.51v. can this be a reason ??? I identified this voltage come to PT1502 through a SMD type FET (number is not printed). When switch is off, 4.07V come to the switch, but it’s dropped 2.51 when button is pressed. Can this happened due to a short-circuit on the FET or PT1502? Please give me a hint to respire this .

    • Device: 7’’ e book reader (Chinese, brought from ebay)
    • Li-iron cell : 3.7V 2000mAh ( Tested, it’s fully charged )
    • please see the all attached files.
    • Have you used PT1502 ?
    • CPU : RK2738 Rockchip
    • PCB: HTC-E001N
    Thanks friends

  2. KJ6EAD

    Senior Member

    Apr 30, 2011
    It's a Haisung Technology model 1789. They have a 1-year warranty which is mentioned about 2/3 the way down their FAQs. You've voided the warranty but I won't tell them.
  3. ranatungawk

    Thread Starter Active Member

    Oct 30, 2008
    thanks for the hint. but ebay items dont have a warranty