Hi all.
Don't know if anyone can help with this. I have acquired a cheapo brand Plasma TV with 2 faults. The most serious problem is that the picture is very dark through all analogue inputs (aerial, SCART, VGA), it looks similar to a lack of luminance signal (Y). HDMI input is fine, as are the on-screen menus, so this is obviously a failure on the main PCB. If I can solve the other issue below I will attempt to fault find this board, but I have a feeling the main Digital signal processor is faulty (the Genesis chip).
Anyway, more importantly the display has a very common fault as in maldischarge (speckles) this is random all over the screen and noticeable mostly on black areas or light to dark transitions. The display is know for this problem (LG PDP42V7) I have a manual for the PDP, have checked and replaced all electrolytics on the Y-SUS board with no effect. Have also done a full set-up (Vs,Va,Vsc,-Vy and Vzb) as well as the Vsetup and Vsetdown. Tried a few alterations as well to these voltage levels, I have the display as good as it can possibly be. The issue is not failure of either sustain board in this case, since both waveforms conform to spec. The power supply is good and producing clean voltage rails.
I believe this is a very common fault caused by ageing of the panel, and LG supplied a firmware update for the control PCB to alter the timing of the sustain waveforms to compensate. My problem, I don't have the LG jig to apply the firmware. I know that a kit is available containing the Y-SUS, Z-SUS and Control PCB's, however to me this is not a wortwhile route considering the age of the set and the other (potentially expensive) fault. I'm really only trying to repair this out of curiosity.
Does anyone know how I can apply a firmware update without the LG jig. This is too old to allow an update via any service menu options, it doesn't have any external ports such as USB or Common Interface either. The firmware in this instance is applied directly to the control board (there is a connector for the jig). In reading the service literature it appears the jig connects to a parallel port on a PC and the firmware is then downloaded onto the jig before being applied to the PDP. Any chance I could construct something to do this? No doubt LG use some proprietory interface for which no information is available.
I work for a major company and service Plasma equipment daily (much more modern than this one!), the majority of this is warranty repair work. I also have substantial repair experience as well as doing this for a hobby. I have seen this type of fault many times, but in warranty repair generally the entire PDP assembly is replaced. As I said I'm mainly doing this out of curiosity. If I can't find a solution I will just break the unit and sell the boards.
Apologies for the long message. Please do not reply with "replace the boards/PDP, scrap the TV etc. type messages.
feel free to post this anywhere you think might help.