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Mintek DTV 260 LCD TV - Power stays on, but image pops off

Discussion in 'Troubleshooting and Repair' started by redzep, Sep 6, 2012.

  1. redzep

    redzep

    2
    0
    Sep 6, 2012
    Hi all, first time poster here, hope I do this right!

    Mintek DTV 260 26" LCD TV turns on, input via DVI from computer shows image clearly, and after a certain period of time (3-5 min if its been off, <1min once it's been on… heat?), there is a pop from the speakers and the screen goes dark. This does not appear to be a "power off" since the green light indicating "power on" at the top of the screen continues.

    If no input is attached, we just get a blue screen that says "No Signal" and then it goes into its Backlight power off countdown, so it's tough to verify if the "pop" would happen with no input.

    I've opened up the back, all capacitors appear visually to be fine, no bulging or leaking. I've tested the voltage on all the pins of plugs leaving the power supply board, the results of which I attached below. There are few discrepancies, but they seem OK, and most importantly, the readings don't change after the "pop" vs. before.

    The fact that the power is staying on (green light) makes me think it's inverter board or lamp, but how do I test/repair this?

    Appreciate your help, I will take it in to repair, but am eager to try and fix it myself if possible, if nothing more than for the learning experience.

    Thanks much to all in advance!

    -------------------------------

    C204 to inverter board
    GND: 0
    BKON (?): 3.6
    BKADJ: 1.7v
    GND: 0
    GND: 0
    GND: 0
    GND: 0
    GND: 0
    +24V: 24v
    +24V: 24v
    +24V: 24v
    +24V: 24v
    +24V: 24v

    C205: to main logic board
    +24: 24
    +24V: 24
    GND:0
    GND:0
    -5V: -5.5
    GND:0

    C206: also to main logic board
    BKAJD: 1.7
    BKON: 3.6
    STB (or ST8): 4.6
    GND: 0
    GND: 0
    GND: 0
    +5V: 5.9
    +5V: 5.9
    +5V: 5.9
    GND: 0
    GND: 0
    +12V: 14.7
    +12V: 14.7
     
  2. Jotto

    Jotto

    120
    0
    Aug 24, 2012
    Just because a capacitor doesn't have a bulge that its considered good. Not all of them will blow out. A capacitor starts going bad as soon as its made. You can get some new ones that show bad.

    Your best way of testing is with a ESR meter, an then its not always a good test.

    Have you tried the VGA input? Can you adjust the backlight and see a voltage change?
     
  3. redzep

    redzep

    2
    0
    Sep 6, 2012
    Thanks for the reply, yes good points all. The VGA behaves the same way. Last night I got some news from a veteran TV repair guy who assured me that was almost definitely the main logic board in those Mintek models, so I went ahead and ordered a replacement board, though it has a complete refund policy in case it doesn't work. Keep you posted!
     
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