August 19, 2009 8:47 AM PDT

Panasonic fixes X1 plasma screens, but questions remain

Faint diagonal lines are a thing of the past on new Panasonic TC-P50X1 plasmas.

(Credit: Sarah Tew/CNET)

When I reviewed Panasonic's entry-level 2009 50-inch plasma TV back in April, the TC-P50X1, I mostly liked what I saw aside from one strange issue: the screen showed faint diagonal lines seemingly embedded in there. See the bottom of this post if you're interested in the full description from the review.

Fast-forward to late July, more than halfway through the product's lifespan, and it seems Panasonic has fixed the problem. The company sent yet a third TC-P50X1, and it didn't exhibit the diagonal lines.

That's all well and good, and Panasonic deserves credit for finally addressing the problem. But questions remain, and Panasonic has not been forthcoming.

On August 12, I asked the company a series of follow-up questions, including, "Exactly when did the change get implemented? Did the 42-inch model have the same problem? If so, was the same change implemented? Is there any way for a consumer who's shopping for an X1 plasma to tell whether the panel is an old one or a new one, aside from looking directly for the diagonal lines? Is there any sort of serial number cutoff? Can current owners who have the old, flawed panel exchange it for a new one? If so, how?" and, "Please provide an explanation of what the lines were and why they're present on the old one and not the new one."

What I've received in response after a week of waiting for a reply was pretty unsatisfying.

"A change was made in early production and that we will help customers directly. They need to call our call center at 800-211-PANA (7262)."

My follow-ups to that vague statement also went unanswered by the time this blog posted, although if the company does provide further explanation I'll post an update.

In the meantime, the best advice I can give to current owners of the TC-P50X1 who are bothered by the lines is to call the number, describe the issue you see, and cross your fingers.

I did compare the boxes of the two latest 50X1 models I had in-house, and found the following information:

Old (with lines)
Manufactured: March 2009
Model Number: TC-P50X1
Serial No: LB90610756

New (no lines)
Manufactured: June 2009
Model number: TC-P50X1
Manuf ID No: TC-P50X1N
Serial No. from back of TV: MF91690203N

Stickers pulled from the boxes of the respective TVs show the mysterious "N."

The new model has a "Manufacturing ID No." that reads "TC-P50X1N" on the back panel as well as on a small ticker applied to the box (see above). The "N" also appears after the serial number on the back of the TV, but not after the serial number on the sticker. In all other ways, including the big sticker on the back, writing on the box itself, and of course the company's Web site, it's still identified as simply "TC-P50X1." Perhaps the Ns denote "new" and indicate a "fixed" TV with no lines, but there's no way to be sure. Unless Panasonic wants to start talking, that is.

Until that happens, we recommend that potential X1 buyers who want to avoid the lines look for an N or at least a manufacturing date of June 2009 or later. If they can get a line-free X1, they'll get an even better-performing entry-level plasma than ever.

Passage from the original review:

Most plasmas have nearly perfect screen uniformity, to the extent that we usually skip this section entirely in plasma TV reviews, but on the TC-P50X1 we encountered an issue we hadn't seen before. It might not be a classic uniformity artifact, such as off-angle problems or brightness variations across the screen--which were, as expected, basically nonexistent on this plasma--but it could be a deal-breaker for sharp-eyed viewers. Then again, most viewers probably won't notice it, at least until they read about it.
From seating distances closer than about 10 feet, we could make out a pattern of very faint, grayish diagonal lines that ran from the upper left to the lower right of the screen. The lines didn't move, but rather seemed to be a part of the screen or pixel structure. They showed up most in lighter areas, such as flat fields like the sky above the hospital and gray or white walls, as well as in lighter-skinned faces like that of Jody Foster as she stares at the newspaper clippings. In darker or noisier material the lines became much less apparent and often disappeared, but in many instances we could easily make them out--more easily the closer we sat to the screen (we find a seating distance of about 8 feet comfortable for a 50-inch screen). Once we noticed them, it was difficult to "un-see" the lines. Test patterns confirmed that the entire screen was affected.
We described what we saw to Panasonic, and the company's engineer said he would get back to us with an explanation. Panasonic did send us a second TC-P50X1 when we asked for it, to make sure that the issue wasn't confined to our particular review sample. Both looked basically the same, and both showed the lines. No adjustment we could make eliminated the issue.
Updated on May 28, 2009: The company got back to us with an explanation: "[Panasonic is] aware of the issue, but currently there is nothing that can be done to alleviate the lines. It is thought to be interference between the panel and front glass. At this time, a fix or software update to correct the phenomenon of the diagonal lines is not available. Engineers in Japan are continuing to study the phenomenon and investigate possible solutions and/or countermeasures."

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