Announcement

Collapse
No announcement yet.

Benq Q7T3 - Only Brief logo flash - steady green but NO GO

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Benq Q7T3 - Only Brief logo flash - steady green but NO GO

    Apologies if this post should be somewhere else. I started this thread because I do not have the flashing or amber/green light as some others do.

    Replaced all 2sc5707 trannies with genuine - [prior to that there was a very dim brief logo flash and power light steady green.]
    Now I get a far brighter [its at normal??] logo flash - steady green light but otherwise situation is unchanged.

    No signs of excess heat - fuses check ok and have resoldered inv. transformers and all electro caps.

    As most of you seem far more technically adept than me, I would really appreciate some guidelines to tracing this no go fault.
    Thanks
    [Found 3 sources of very cheap 2sc5707 in Australia - if anyone wants info email me.]

    #2
    Re: Benq Q7T3 - Only Brief logo flash - steady green but NO GO

    Someone suggested Q743 and Q751 [FU9024N] should also be replaced. Mine are marked J598 and look identical in style as the 2sc5707's - so need info on this too please. Mine look to be originals.
    Thanks

    Comment


      #3
      Re: Benq Q7T3 - Only Brief logo flash - steady green but NO GO

      The steady green light indicates your video signal is being received the logo flash indicates that the inverters or lamps have a problem. You need to eliminate stage by stage. Seeing that it has flashed again first check the FU9024N transistors for any short. Are you checking the right fuse? A small wired fuse looking like a resistor PF751 on the schematic is the important one, they sometimes look OK but must be checked with a continuity tester (low ohms multimeter). Recheck the 2SC5707 transistors for shorts, it can happen again if the original problem was not fixed. Try each backlight tube seperately, swap the plugs, this is to see if one inverter or lamp is a problem.
      If you have already resoldered all transformer connections also check the capacitors C754,C755,C734, C735 that are connected across each inverter transformer primary and occasionally fail.

      Where are the cheap 2SC5707 in Australia?

      You may need to find an FU9024N (IRFR9024N) P channel MOSFET rated at 11 amps. Yes they are in the same package as the 5707 but very different.

      Hope this helps.
      Gigabyte EP45-DS3L Ultra Reliable (Power saver)
      Intel E8400 (3000Mhz) Bios temps. 4096Mb 800Mhz DDR2 Corsair XMS2 4-4-4-12
      160Gb WD SATAII Server grade
      Nvidia 8500GT 256Mb
      160Gb WD eSATAII Server grade for backup.
      Samsung 18x DVD writer
      Pioneer 16x DVD writer + 6x Dual layer
      33 way card reader
      Windows XP Pro SP3
      Thermaltake Matrix case with 430W Silent Power
      17" Benq FP737s LCD monitor
      HP Officejet Pro K5300 with refillable tanks

      Comment


        #4
        Re: Benq Q7T3 - Only Brief logo flash - steady green but NO GO

        Davmax thanks - but I get a steady green without any signal..is that a further clue tothe prob??
        Unsoldered one leg of the small fuse to check - was showing about 150 ohms resistance in the 'beep' mode.
        The two Fets seem ok - no shorts if tested leg to leg but that may not be the correct test for them
        Last edited by MikeM; 05-13-2008, 07:50 AM.

        Comment


          #5
          Re: Benq Q7T3 - Only Brief logo flash - steady green but NO GO

          Fuse is bad if 150ohms should be zero. If you do not read a short across the legs of the MOSFETs then no shorts.
          Odd that light is green without signal. The presence of video signal controls the back light controller chip. But first replace the fuse. I have a heap I can pop a couple in an envelope if you like.

          Who are the 5707 suppliers?
          Gigabyte EP45-DS3L Ultra Reliable (Power saver)
          Intel E8400 (3000Mhz) Bios temps. 4096Mb 800Mhz DDR2 Corsair XMS2 4-4-4-12
          160Gb WD SATAII Server grade
          Nvidia 8500GT 256Mb
          160Gb WD eSATAII Server grade for backup.
          Samsung 18x DVD writer
          Pioneer 16x DVD writer + 6x Dual layer
          33 way card reader
          Windows XP Pro SP3
          Thermaltake Matrix case with 430W Silent Power
          17" Benq FP737s LCD monitor
          HP Officejet Pro K5300 with refillable tanks

          Comment


            #6
            Re: Benq Q7T3 - Only Brief logo flash - steady green but NO GO

            umm.. for the green led without a signal:

            maybe someone turned off the energy saving stuff in the OSD menu...!?

            its possible on my lcd. if energy saving is turned on and you power up the monitor without a signal it displays a logo for 2 seconds and then goes into standby (orange/yellow led). if the energy saving stuff is turned off and you turn the lcd on it displays the logo for 2 secs and stays on (green led) with black screen and backlight on if there's no signal.

            unfortunately you cant go into the OSD menu if there's no signal on most LCDs.. (mine simply says "No Signal" no matter what buttons i press.. have to give it a signal to get into the menu..)

            Comment


              #7
              Re: Benq Q7T3 - Only Brief logo flash - steady green but NO GO

              Hey its working - problem with mine obviously was 1 bad 2Sc5707 transistor and 1 3amp fuse [that seemed to be ok] - but as DavMax suggested I replace it, I did, and the screen was working again.

              Thanks to all the offered help esp. DavMax. Hope someone else finds their fix is as simple [when you know how to] as mine was.

              MikeM

              Comment


                #8
                Re: Benq Q7T3 - Only Brief logo flash - steady green but NO GO

                I have same problem. How do i check the FU9024N transistors? What else should i check for? There is no flash of the logo anymore. The first test showed a logo. After that, it was nothing.
                Whats Q743? is it also a FU9024N

                Comment

                Working...
                X