LG 50PC1D problem....with video!!!:)

[orion_carl]

Hi all!
my name is Carl and I am a engineer for Hotpoint!so TVs aren't my normal area, I used to repair tube TVs before machines, so I have a good understanding of how they work ect.
My problem with my TV is the picture is scrambled, dots, lines.
Sound is fine, I replaced the control board, but didn't fix the problem!
I can "get" the test card, but its scrambled to,when off a input, I have a white bar that moves around the screen in sequence, but when on the scart socket, its just colours that move with the DVD playing, i'm now off at looking at the Y sustain board, but if someone could watch the video and help me further, like, the lights that are on, is that correct?I also have the service manual, but it doesn't really have this fault listed.
thank you for any help

http://www.youtube.com/watch?v=f8WuuH0FpKc

[tom66]

Re: LG 50PC1D problem....with video!!!

Looks like Y-sustain.

Failures I've noticed when various boards go out:
- Y buffer boards: No picture/half picture/horizontal lines
- Z-sustain: Dark purple or dim fuzzy picture
- Y-sustain: No picture/random colour effects like in your video
- X buffer boards: Vertical lines
- Low PSU voltages: Visible picture but very poor colour, or pixels are firing randomly

The fact that you are getting some patterns - I think that means your control board is okay.

Also note that sometimes it takes time to change from pattern to pattern esp 0:36. That is a good sign of a failed Y sustain...

If you have an oscilloscope, you can check the sustain boards, but I don't know if fixing Hotpoint appliances requires one?

[orion_carl]

Re: LG 50PC1D problem....with video!!!

thanks for the quick reply!
sadly I don't have one!
would you say it would only need the y-sustain board, I guess is the one on the right of the back of the TV?or all the boards?
I've also replaced the 9 caps in the power supply.
thanks again.

[tom66]

Re: LG 50PC1D problem....with video!!!

thanks for the quick reply!
sadly I don't have one!
would you say it would only need the y-sustain board, I guess is the one on the right of the back of the TV?or all the boards?
I've also replaced the 9 caps in the power supply.
thanks again.

Easiest way to identify y-sustain is it is usually the bigger of the two driver boards on each side of the panel and it is usually connected to one or more buffer boards... z-sustain is connected straight to the panel.

Doesn't sound like bad caps... but do you have a multimeter?

[orion_carl]

Re: LG 50PC1D problem....with video!!!

yeah bud, I use one daily, handy bit of kit!I don't want to fork out for a board if it doesn't need it!!ive taken out the y-buffers to test them..found a online bit about them to check!

[tom66]

Re: LG 50PC1D problem....with video!!!

yeah bud, I use one daily, handy bit of kit!I don't want to fork out for a board if it doesn't need it!!ive taken out the y-buffers to test them..found a online bit about them to check!

Can you post a pic of the back of the TV? Clear and in focus. Specifically, I'm interested in the power supply and Y-sustain, so clear pictures of those in addition to a shot of the back of the TV would be helpful.

I assume you are competent in using a multimeter, so would you understand what I said when I told you to set the meter to max volts DC (e.g. 600, 1000V - depends on the meter) and probe a specific connector? There is a voltage called Vsus, which is usually 190 - 220V (depending on the plasma panel itself) which must be within a certain range for the picture to work.

[orion_carl]

Re: LG 50PC1D problem....with video!!!

yeah tom i'm pretty handy with a multimeter so testing bits isnt a problem!I will do some pictures in a second, I noticed yesterday when I left it on for about 30 mins, the whole screen started to flicker, and I could hear a slight noise on the sustain board from under the large heat sinks?
thank you so much for your help so far

[orion_carl]

Re: LG 50PC1D problem....with video!!!







let me know if you need any more or any better!

[tom66]

Re: LG 50PC1D problem....with video!!!

Can you get a closer pic of the power connector on the Y-sustain (it goes from Ysus to power board) I'm hoping there's a legend next to it to determine which pin is which..

[orion_carl]

Re: LG 50PC1D problem....with video!!!



there you go tom

[tom66]

Re: LG 50PC1D problem....with video!!!

there you go tom

Okay we have two voltages Vs and Va both relative to ground.

Vs is usually 190 - 220V
Va is usually 40 - 70V

(it all depends on the exact panel used)

On the back of the plasma panel itself (which everything is bolted to) there is probably a sticker which tells you what each voltage should be. What are the rated voltages? Usually there are three: Vs, Va and -Vy (or Vsc, or Vsetup - depending on mfgr) - sometimes a Ve voltage is used too.

With your multimeter, connect the black probe to an exposed part of the metal frame (but not the power supply.) Any metal screw hole will do. While the set is off, try to stick the red probe carefully into the Vs and Va connections, either on the power supply or main board. Then turn the TV on, and measure the voltages. Report back, along with those rated voltages.

[netdent]

Re: LG 50PC1D problem....with video!!!

If any help carl I'm sure I scrapped one of these sets with a smashed screen and kept all the boards

cheers Ronnie

[bigedinphoenix]

Re: LG 50PC1D problem....with video!!!

Hi Im Ed, I could sure use the boards you kept out of tv you scrapped. have a tv that needs them.

[netdent]

Re: LG 50PC1D problem....with video!!!

Hi Im Ed, I could sure use the boards you kept out of tv you scrapped. have a tv that needs them.

Hi Ed, waiting to see if Carl needs any then we can talk

cheers Ronnie

[orion_carl]

Re: LG 50PC1D problem....with video!!!

sorry for late reply!!right
VA should be 60v and its spot on 60v

VS should be 193v and its 192v

so that seems spot on!
"tested" the y buffer is this a good reading??
its infinite the other way

[tom66]

Re: LG 50PC1D problem....with video!!!

I can't quite see what range you have it on. If on 1k ohms, 498 ohms is low, but not too low to cause problems. You are looking for <10 ohms for a short.

However, a bad buffer is unlikely to cause your problem, as it affects both halves of the display. A bad buffer will usually only take out half of the display, or cause no picture at all because it shuts down the Y-sustain. (In rare cases you can get horizontal lines, too.) However, you have a total display failure, you still have a picture but it's all messed up.

At this point I would say look at getting a new Y sustain, as they are usually fairly inexpensive on eBay.

[caspermccormack]

Re: LG 50PC1D problem....with video!!!

Okay we have two voltages Vs and Va both relative to ground.

Vs is usually 190 - 220V
Va is usually 40 - 70V

(it all depends on the exact panel used)

On the back of the plasma panel itself (which everything is bolted to) there is probably a sticker which tells you what each voltage should be. What are the rated voltages? Usually there are three: Vs, Va and -Vy (or Vsc, or Vsetup - depending on mfgr) - sometimes a Ve voltage is used too.

With your multimeter, connect the black probe to an exposed part of the metal frame (but not the power supply.) Any metal screw hole will do. While the set is off, try to stick the red probe carefully into the Vs and Va connections, either on the power supply or main board. Then turn the TV on, and measure the voltages. Report back, along with those rated voltages.

Hi, sorry if I'm hijacking this tread, I have the same tv with I believe to be a power board issue, I do not get a reading on either the Vs or Va on my board. All other voltages are present (3.4,19,12,6 and 5) The tv trys to turn on and then switches off after 3-5 seconds. Any help would be great, thanks.

[tom66]

Re: LG 50PC1D problem....with video!!!

Try unplugging the Y-sustain board and seeing if it turns on. Looking from the back of the TV, the board is on the left hand side, and is the largest of the two boards connected to the plasma panel.

In a dark room, does the screen flicker just before turning off? If so you have an AC Detect problem, which I have seen quite a lot with the 42" and 50" PC series plasmas from LG. I'm not sure why, but it's an easy fix (just requires a bit of solder, not even a component to replace.)

[retiredcaps]

Re: LG 50PC1D problem....with video!!!

Hi, sorry if I'm hijacking this tread,

This is the 3rd thread you have started. This only confuses regulars as to what information is relevant and the latest. Keep it in ONE thread otherwise we hit next thread with no regrets.

[caspermccormack]

Re: LG 50PC1D problem....with video!!!

Sorry about that.