How I "fixed" the display on an Akai LT-3220AD TV
Good day folks. I thought I'd share with you something I did today, just for a laugh and for a bit of a discussion, since I'm still not entirely convinced what happened there.
I found an Akai LT-3220AD TV in the dumpster - literally - so me and my colleague brought it back into the shop and dusted it off a bit to see if someone maybe gave up too soon.
Long story short: backlight came on but had no picture. My colleague attempted to reprogram the SPI chip but it didn't change anything, so we concluded it must be the panel that's faulty, especially after reading about it online and finding videos of others showing this fault and how to patch it up, for example this video, which shows almost the exact panel, with the exception of the buffer board itself which in our case is a MT3151A05-3-XC-1, while his an MT3151A05-9-XC-1. The panel model itself is KM315e6-cs-12.
I wasn't able to replicate his results though, because my buffer gave me no VGH and VGL at all. The VGL test point was actually reading around 9ohms resistance to GND, so that wasn't going to work. Not having anything to lose, I did what any skilled tech should do at this point and that is.............hook that test point up to my bench power supply and start pumping
Ok, I wasn't that much of a doof - I at least had the courtesy to go slow and not go over -6v, since I hooked the positive of the supply to the chassis and the negative to the test point itself. There was no current draw at all, so nothing spectacular happened.
After that, I decided to have one final go with the multimeter and check the resistance on VGL again, since it didn't make sense: I just had a low-ish resistance, there should've been at least some current flowing somewhere. Guess what: the resistance was now up in the kilo-ohms range....dafuq ? Ok, but surely I won't get any voltage there, right ?....wrong: I now got -7v on the VGL test point.....AND picture on screen ! The TV works now....the picture is just fine too ! I thought for sure it would be a mess of colors and "ghosts", but no - perfectly usable !
Ok, so I guess this is how we fix things nowadays: hook them up to the power supply and blow up whatever's shorted
Realistically, I think what happened is I blew up whatever "gate" (?) was shorted on the COF, but it happened too briefly to show up on the ammeter. The power IC on the board was not designed to deliver current until something popped, so it immediately shut down upon startup, whereas my bench supply knew no such thing...
I found an Akai LT-3220AD TV in the dumpster - literally - so me and my colleague brought it back into the shop and dusted it off a bit to see if someone maybe gave up too soon.
Long story short: backlight came on but had no picture. My colleague attempted to reprogram the SPI chip but it didn't change anything, so we concluded it must be the panel that's faulty, especially after reading about it online and finding videos of others showing this fault and how to patch it up, for example this video, which shows almost the exact panel, with the exception of the buffer board itself which in our case is a MT3151A05-3-XC-1, while his an MT3151A05-9-XC-1. The panel model itself is KM315e6-cs-12.
I wasn't able to replicate his results though, because my buffer gave me no VGH and VGL at all. The VGL test point was actually reading around 9ohms resistance to GND, so that wasn't going to work. Not having anything to lose, I did what any skilled tech should do at this point and that is.............hook that test point up to my bench power supply and start pumping
Ok, I wasn't that much of a doof - I at least had the courtesy to go slow and not go over -6v, since I hooked the positive of the supply to the chassis and the negative to the test point itself. There was no current draw at all, so nothing spectacular happened.After that, I decided to have one final go with the multimeter and check the resistance on VGL again, since it didn't make sense: I just had a low-ish resistance, there should've been at least some current flowing somewhere. Guess what: the resistance was now up in the kilo-ohms range....dafuq ? Ok, but surely I won't get any voltage there, right ?....wrong: I now got -7v on the VGL test point.....AND picture on screen ! The TV works now....the picture is just fine too ! I thought for sure it would be a mess of colors and "ghosts", but no - perfectly usable !
Ok, so I guess this is how we fix things nowadays: hook them up to the power supply and blow up whatever's shorted
Realistically, I think what happened is I blew up whatever "gate" (?) was shorted on the COF, but it happened too briefly to show up on the ammeter. The power IC on the board was not designed to deliver current until something popped, so it immediately shut down upon startup, whereas my bench supply knew no such thing...