Cross a sharp LCD TV with a BenQ, what would you get? (Part4)

Discussion in 'General Electronics Chat' started by R!f@@, Jun 3, 2009.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Below is a pic of the tube connection and powered up.

    [​IMG]

    Next was to mount the Inverter. Since the BenQ one was of low profile type, the sharp one will never fit the BenQ's inverter mounts. Again I have to compromise.

    [​IMG]
    [​IMG]

    I have to get rid off the BenQ speakers to mount the Inverter, Since the Tube connectors have HV Insulation and any longer wire than necessary will tend to generate a lot of EMI, second getting HV insulated wires is impossible here, and also the mechanical work associated in all these modification will cost a lot and will take a lot of time, this was the best option. Besides I never like the small speakers it has, and I have a 7.1 one custom built sound system with my HTPC, I do not need any more speakers. . And my audio Rocks. hehehe!!

    In the second picture u can see the plastic I used to insulate the inverter since I got electrocuted ones or twice without it. I'll say it was quite an experience touching the HV.
    The plastic is quite nice isn't it, I have a cousin who is in business with laser cutting and engraving all kind of materials. The laser engraver is quite unique and one of a kind here, I can make any thing with it, and I am thinking of making bezel facia for this TV, with all the art works and stuff, but that will be a bit later.
    The plastic provides a solid mount to the chassis.
    The tube connections a kept to a minimum and has HV heat shrink tubing to prevent unnecessary arching to the chassis. Still I donno how long the insulation will hold, it is yet to be tested how long it will take the tubing to degrade.

    [​IMG]

    Finally Inverter Assembled

    Next comes the PSU modification, but before that a lot of measurements were taken about the voltages and current ratings. I wasn't going to use both the supplies in it, no place to mount and it will generate too much heat and consume unnecessary power.

    Initial testing was done without the inverter and with the benQ PSU to see how much power is consumed by the panel and the axillary circuits.
    The BenQ Panel was using the LVDS signal and mainly the Auxillary supply like 3.3V, 2.5V and 1.2V that was neccessary for the panel and DSP is regulated by onboard switching regulators on the DSP Assy and all it needs was 12V @ 0.5A and a 5V at around 1.5A tops. The audio amp uses complementary 16V supply and the inverter is powered by a bulk 14V.
    The switching voltage necessary to turn on the PSU from stand by and inverter is @ 3V. Plus a stand by 5V @ 0.5A.
    Since I attended the sharp PSU before I was quite familiar with it's voltages. 400V DC to the Inverter, Complementary 14V to the audio, two 3.3V @ 1.5A, 6V @ 1.5A and a stand by of 3.3V.
    So replacing the BenQ PSU with the sharp one is childs play. Only problem was the ever 5V needed by the BenQ DSP, and it will not operate if it drops even by 0.5V.
    I have to use a seperate 5V PSU to oparate the BenQ DSP at stand by and modifiying the sharp ever 3.3V is really difficult since this ever 3.3V feed back loop is cuopled with the charge pump circuit in the sharp PSU, any change I brought to increase the 3.3V to 5V hinders with charge pump operation. And making a charge pump takes more time, and I was in such a hurry to get the TV in to my room [​IMG].

    [​IMG]

    Here you can see a small 5V PSU I salvaged from my junk. suites well, doesn't it? Well that's settled.

    Part 5
    Rifaa
     
    Last edited: Jun 3, 2009
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