Philips 40PFL7007K/12 does not power on - Chassis QFU1.1E LA

Discussion in 'General Electronics Chat' started by MartinJ, Jan 22, 2015.

  1. MartinJ

    Thread Starter New Member

    Jun 4, 2014
    4
    0
    Hi everybody,

    I have Philips 40PFL7007K/12 on repair. TV does not start up. I have checked the PSU and it seams to be OK. There seam to be problem on the main board.

    What I have tried…

    Well, there is +3V3-STANDBY coming from PSU to main board. This feeds up the main processor. This voltage has also been used to switch TV on. I have checked that switching signal from POWER ON button goes back to main board. But I did not check this whole path towards the processor as it is BGA package and it is covered by ceramic cooling plate.

    And here comes what is not clear to me.

    1. How to check if the main processor works? Does it work on the +3V3-STANDBY when TV is is standby mode?

    2. Can I somehow check if the PSU is working? May be by activating some pin?

    3. I have noticed by measuring (ohm-meter) some capacitors on the main board (in circles on the picture) that there is very low resistance on them (4.5ohms). In the scheme it is shown that these capacitors are on the 1V5 (1.5V) line. Is this OK? Basically it does not give much current as I = 1V5 / 4R5 = 333mAmps. What do you think? Certainly there are low voltage data parts (RAM. Processor …) connected and such resistivity might be correct….?....
    What I have also find that this 1V5 is split into 1V5M0 and 1V5M1. See the picture. I have removed the coils and measured resistance. Then 1V5M0 shows about 15ohms and 1V5M1 shows about 6,5ohms.

    The service manual link:

    http://ulozto.net/xmFJspug/philips-ch-qfu1-1e-la-pdf

    Thanks Martin

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