LG EAY62171101 Plasma Power Supply

[Schoenradt]

Hello All reading this post. Once again I will try to explain my misfortune. I am trying to repair an LG EAY62171101 plasma power supply board. I almost have it working, however on the foil side of the board it seems that R904 is damaged so I have taken a closeup image of that area on the board. They say a picture is worth a thousand words so please view it and let me know if anyone out there can get back with me on the value of R904.

[R_J]

Re: LG EAY62171101 Plasma Power Supply

It will be the same as R905 (33kΩ)

[Schoenradt]

Re: LG EAY62171101 Plasma Power Supply

Thanks for the information. How did you get a schematic for this power supply? I can't find it anywhere and LG is useless on divulging technical information. Checked and not even Sam's Photofact doesn't have it.

[R_J]

Re: LG EAY62171101 Plasma Power Supply

Thanks for the information. How did you get a schematic for this power supply? I can't find it anywhere and LG is useless on divulging technical information. Checked and not even Sam's Photofact doesn't have it.

The circuit is common and is from a different board.

[Schoenradt]

Re: LG EAY62171101 Plasma Power Supply

I have ordered 33kΩ resistors from Digikey. It looks as the physical size is 1/8 watt based on metric size 3mm by 1.6mm. Getting excited to get this TV working have spent a few hours checking capacitors and voltage levels. I did substitute a pot for 32kΩ and the set did power on, but no plasma ionization. I have the Sencore LC103 LCR analyzer and it tests components both in and out of circuit. I have another 50" plasma with the front tinted glass broken, but the tube seems intact. From what I've read a plasma screen will work even if it's cracked because the cells are separate just like a chain of neon bulbs. I won't know until I get that power supply back on line again. It's an older model EAY60713401.

[R_J]

Re: LG EAY62171101 Plasma Power Supply

If the plasma panel is cracked and the gas has leaked out it will not give a picture. Sometimes the panel seal (between the two glass plates) goes bad and the gas leaks so no picture. I have seen a cracked panel that was still working but the crack was short and still tight so the gas did not leak yet, but over time it could.
I have seen panels that have leaked and if the rest of the tv still works, they can make a strange noise that seems to come from the center of the panel and the pitch will change based on the video signal.
The wattage of the resistor is low, no need for a high wattage, the current through it is very low.

[Schoenradt]

Re: LG EAY62171101 Plasma Power Supply

The power supply board now works and all the voltages rated on the chassis are in value, however the Vy, Vsc, and Vzb are extremely low. I'm guessing these voltages are derived by EAX62846401 Ysus board. Unable to find any schematics or troubleshooting guides for putting the board on an external power supply and checking voltages with my oscilloscope.The set does now power on but no raster or sound.

Any suggestions where I can get a schematic for the ysus board EAX62846401?

Also the upper video buffer board did have a shorted IC it was replaced with a new board as I destroyed the old one trying to remove the chip. I used to much heat and several traces were lifted off the board with the chip. I am saving the board to practice trying to remove the other chips without damage to the board.

[R_J]

Re: LG EAY62171101 Plasma Power Supply

I doubt you will ever find a schematic on this board
Have you checked the fuse FS203 on the Y-sus board? Also FS201, FS501 and FS202.
Vy & Vsc are derived from the circuit that is driven by IC500, the ic drives the transformer T500 primary and there are two diodes, D503 & D504 that supply each of the Vy and Vsc voltages

[Biruslapio]

Re: LG EAY62171101 Plasma Power Supply

This model is doomed, all of 50PTXXX and 50PWXXX are, project failure that overheats and blows the buffer ICs, the best use these TVs can have is extracting the Y-SUS and Z-SUS IGBTs, and using the motherboard on a 42PT/PW model.

Here all these 50PT models use PDP50T30010panel, EAX63333201 control and EAX62846401 Y-SUS, a LOT of these appear for sale with 90% upper or lower buffer failure, shorting or blowing up, any of the Y buffers cost 50% of the TV when one appears for sale and they sell out fast, if yours have the same parts, nothing much you can do besides fixing it and wait for it to fail again.

You still have a short on the buffers or it damaged your Y or Z boards, probably some resistors have opened.

50PWXXX uses PDP50T30000 panel, only difference is that PW models have 3D support.

[ReeceyBurger123]

Re: LG EAY62171101 Plasma Power Supply

This model is doomed, all of 50PTXXX and 50PWXXX are, project failure that overheats and blows the buffer ICs, the best use these TVs can have is extracting the Y-SUS and Z-SUS IGBTs, and using the motherboard on a 42PT/PW model.

Here all these 50PT models use PDP50T30010panel, EAX63333201 control and EAX62846401 Y-SUS, a LOT of these appear for sale with 90% upper or lower buffer failure, shorting or blowing up, any of the Y buffers cost 50% of the TV when one appears for sale and they sell out fast, if yours have the same parts, nothing much you can do besides fixing it and wait for it to fail again.

You still have a short on the buffers or it damaged your Y or Z boards, probably some resistors have opened.

50PWXXX uses PDP50T30000 panel, only difference is that PW models have 3D support.

Just replace the buffer Ics themselves.

[Biruslapio]

Re: LG EAY62171101 Plasma Power Supply

Yes, you can replace the ICs too, most come with Renesas R2A20296FT, but there are many threads on brazilian electronics forums about this TV having Y-buffer failures.

I suggest to OP test the ZBias(Z-SUS), -VY and VSC(Y-SUS) without the buffers connected to the Y-SUS.

[Schoenradt]

Re: LG EAY62171101 Plasma Power Supply

Yes, quite correct all voltages are now specified with sticker on chassis. I found a bad video buffer chip on the lower buffer board IC 204. Since I trashed one of these boards trying to remove the chip I am going to practice removing the remaining 3 chips. This will allow me practice in order to successfully replace the defective IC 204. I find no shorts on any other chips on the lower video buffer board. I did view a very good YouTube video showing removal and installation of this chip and it looks as they used a hakko fr-801 hot air rework station with a 4.4mm nozzle. They show focusing the heat on the center of the chip and briefly heating the pins to avoid tearing up the traces. Also anyone know what type of chemical removes the rubber cement around the pins of the chip? It also seems you need to use a rosin paste flux to insure proper wetting of the solder.

[ReeceyBurger123]

Re: LG EAY62171101 Plasma Power Supply

Send it to me I can do it, the whole lot and I’ll provide heatsinks and thermal glue.