Wanted to share my experience solving a convergence issue on my PT-51HX42 (other Panasonic rear projection sets are similar).
Red convergence was way off one day, and doing some research, I discovered a common failure is the STK392-110 convergence amplifiers that this set uses. Pulling the back off, it was easy to locate these two chips on the left side near the tuner/inputs attached to huge heat sinks.
I ordered STK392-180 chips as replacements as they can deal with heat and power better and are direct replacements otherwise. Here's some tips below:
* Detach the 9 cables on the convergence/tuner board, but leave it attached to the power board, you'll have enough room to work with
* Get a good deslodering tool as each chip has 18 pins
* When you detach the chips from the heatsinks via 2 screws each, you WILL strip the heads as they used very soft brass screws. Plan on getting new ones from Home Depot or Lowes as well as new washers.
* With the chips out, measure the resistance of the handful of resistors nearby. It's easy and they should all be labeled. Mine were all within 10% of rated.
* Make sure you get some good heat sink compound. I used arctic silver from a CPU cooler
* Putting the new chips in place will be a pain because the leads bend easily, so just be patient
* Screw the heat sinks to the chips first such that they'll dissipate heat from the soldering iron
* Have lots of light while soldering
* If you plug it all back in and it flashes the power LED 3 times, recheck your solder connections. You can trace the solder points to the traces on the board easily.
* If you plug it all back in and it flashes the power LED slowly on and off, check to see if you have any shorts. It's easy to do due to the proximity of the pins on the chips. Fortunately the circuit is robust, so it's unlikely to blow anything. Note that the top two pins of each chip ARE supposed to be connected to each other electrically.
* If it all comes back on, you'll likely have to play with convergence. The menus will get you 1/2 way, but be sure to enter service mode and do that convergence as well. To do this, set your input to cable, set the self timer to 30 minutes, exit the menus, tune channel 124, hold the volume down button on the set (not the remote) and you'll get a "CHK" in the top left. Hit the power button on the remote and navigate to the fine CONV settings. You mostly want to play with the red point and blue point settings. You can cycle through them with the "1" key on the remote, and to enter them, use Mute. Then move your cursor via remote, and hit mute again, the remote then can pull convergence as needed. Hit "7" to save and exit. Power the set off via the buttons on it and you're all set. Note that convergence for 480i and 1080i need to be set separately. If you want to set 1080i, after the CHK appears, use video input selector to tune to a HD signal and do the same steps.
Good luck! Feel free to contact me for more info if needed.
on Jun 25, 2008 | Panasonic PT-51HX42 51" Rear Projection...