Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

[aaronwt6]

I have the smaller twin here to my personal TV. I'm trying desperately to get it going to give to my in-laws for Christmas next week. The TV had a shorted SC board which I managed to fix last night with a repair kit. Tightened loose screws all over the place when I re-installed the board. Powered it up and was very happy to see the menu pop up. However, upon viewing for a minute I realized that there was a blue haze all over the screen. Especially on dark scenes. It also started out with a spot that was much worse in the lower right corner but that improved after a few minutes. The haze however remained. I'm at work now and cannot troubleshoot but was wondering if anyone had any suggestions. Unfortunately, the repair kit took forever to get to me so if I don't order any additional parts by tomorrow I don't see having this ready to leave town with me next Tuesday. Thanks in advance for any assistance and I always appreciate the input and advice.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Oh, one more thing. In the last picture, I tried to show what appears to be temporary image retention. Any lettering or sharp edges on a picture that stays up for more than a couple seconds is leaving blue spots on the screen for 5-10 seconds. I'm sure that's related to the entire problem.

Thanks again for the help!!

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Looks like over-diffusion. Try checking Vsus; should not be too high. Could also be Vad issue on SC board if the set-up ramp is stunted, or Ve on SS board, do you have an oscilloscope?

I swear we've seen something like this before on this forum - not sure what it ended up being.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

No scope Tom. I actually just asked your advice on getting one a few days ago but it won't happen until at least after the 1st of the year. I won't be able to dig back into it until this evening (8-9 Eastern Time US). I will start by checking all the voltages. Certainly wouldn't be surprised if there's an additional issue on the SC board since it was blown and I've just repaired it.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

TV is the same as the 50" and 55" version internally.

https://www.badcaps.net/forum/showth...ght=TC-P50ST30

Like I said, my main issue is my time restraint in taking it to the in-laws for Christmas. Certainly don't mind buying a part if I need to but it's going to have to be by tomorrow at the latest.

[tw2005]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

close up Picture of the SC repaired please. Also location of parts replaced. Any smd resistors missing?

[tw2005]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Actually that issue is only where the SD board drives the panel.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Not sure if this is clear enough. Again, I'm at work until this evening so this is what I took last night.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Parts replaced were:

Q402
Q403
Q422
Q423
D401
D421
R402
R403
R422
R423

No parts should be missing that I know of. Pretty sure no one else had opened the TV prior to me.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Any chance that the buffers got damaged when the SC failed? Nothing tests shorted and the guy said the picture was perfect up to the moment it died on him. I do see that some of the other repair kits come with more diodes and FETs than the one I got. However, seems the 6 I replaced along with the 4 resistors is the most common.

[tw2005]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

SO looks like all the resistors replaced, all 7.5ohm I guess? R422, just looks a bit different, right side in photo.

Did you check the SD SU boards ? second last photo seems to indicate it is SD board that 's having an issue. Could be the SD or SC

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

I believe the resistor you are referencing is just lifted up a tad on one side. The iron I have is a bit large for working on those given their size. All 4 were new and the same. I'm not showing any shorts on either buffer board but that's not to say there isn't something wrong. The problems seems worse on the lower half of the screen, but it's certainly showing up on the entire thing. I was looking for a starting point on what to check tonight. Hate the thought of buying the entire set of 3 boards but I'd do that if I thought it was going to solve the problem.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Also, not sure if this is a factor but I was a bit concerned with how much I had to heat the diodes and fets to remove them. I cut a hole in a piece of foil to shield the remainder of the board while I heated each one but man did I ever have to apply some heat to get them loose. I'd said a good 30-45 seconds on each one with my Weller hot air station on it's highest setting. Was concerned about heating other parts on the board.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

My instinct is telling me that there is something else wrong with the SC based on what the previous owner told me about it looking fine up until the point of failure.

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Personally I doubt SU or SD would cause this issue.
Did you check the ERC IGBT driver IC? (near the inductor)

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Also, not sure if this is a factor but I was a bit concerned with how much I had to heat the diodes and fets to remove them. I cut a hole in a piece of foil to shield the remainder of the board while I heated each one but man did I ever have to apply some heat to get them loose. I'd said a good 30-45 seconds on each one with my Weller hot air station on it's highest setting. Was concerned about heating other parts on the board.

It took me a minute to remove the IGBTs using my soldering iron. I think it's normal, the board is a heatsink for the devices, and consequently can suck away a lot of the heat...

[tw2005]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Also, not sure if this is a factor but I was a bit concerned with how much I had to heat the diodes and fets to remove them. I cut a hole in a piece of foil to shield the remainder of the board while I heated each one but man did I ever have to apply some heat to get them loose. I'd said a good 30-45 seconds on each one with my Weller hot air station on it's highest setting. Was concerned about heating other parts on the board.

I just did my first of this series, had same issue, Doubt it's that. Mine went smooth and I reckon may have put more heat. felt like forever.

not real sure which way you should go if everything is hooked up right and tight. I'll have another look but it really seemed just bottom 50% affected

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

The bottom is worse but look at my 3rd picture as well as the last. It's definitely affecting the whole screen. Tom, I did not check the driver IC. What is it's location and what should I be checking on it?

[tw2005]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

yeah, picture 3 shows more of an issue. Test patterns / full white could be interesting. Does remind me of the SS board I accidentally removed 50% of the drive signal when I tagged a SMD 100 ohm resistor and removed it by accident.

Maybe like Tom is suggesting, something extra damaged like driver ic

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

And yeah, first thing I did was double check all my connections. I sure was bummed when I saw the problem. I fired it up, saw the menu, grabbed a celebratory beer to sit back and watch it for a while, and then saw all the sparkles.