Panasonic TX-21MD4 - Dim picture

[terminus]

I have a problem with my Panasonic TX-21MD4. It's 10 years old and has been used a lot.

Any dark or poorly lit parts of the picture (eg. dark hair or clothing, shadowy areas, or a night scene) are really dim and have hardly any detail or colour. Lighter parts of the image show up better though overall it's a rather murky picture. Not worth watching as it is.

I think it's happened gradually as I never really noticed until I put a barely used Panasonic JT1 portable on and noticed how bright and crisp the picture was in comparison. Both are set at the same brightness & contrast (about 50%).

Can anyone diagnose? Thanks in advance.

[Grumpy Old Troll]

Improvements could probably be made by a decent TV engineer quickly & cheaply on-site in less than 20 minutes.

[terminus]

Thanks Grumpy Old Troll

[Mooly]

Sounds like a low emmision CRT I'm afraid. It's gone "soft"

[Grumpy Old Troll]

Originally Posted by Mooly

Sounds like a low emmision CRT I'm afraid. It's gone "soft"

I hate to disagree with you... But I will.

I've seen lots of these sets over the years. And never seen a "low emmison" or "soft" CRT on one of them. So I'd be very surprised if this one's got one.

Which is why I said a decent TV engineer can probablyimprove things quickly and cheaply on-site. Can't guarantee that of course - without actually seeing the set. But I certainly wouldn't be condemning it without seeing it.

[Mooly]

Hi terminus,

As Grumpy Old Troll suggests, you do have to see it really. It's one of those things an engineer can generally diagnose instantly, to describe isn't perhaps so easy but we'll have a go.

Might be worth looking for any of these (admittedly fairly basic) symptoms,
1. Does it seem to take longer for the picture to appear from a cold switch on than when it was newer.
2. When the picture appears is it "tinted" at all gradually becoming better over a minute or two.
In particular is the red slow to warm up, are faces greenish slowly becoming more natural. Due to the makeup of the signal all the three guns (red green and blue) in the CRT are not driven equally, red is most hard driven. This is a fairly good guide to failing emission.
3. Put something like CBeebies on, you want something with loads of heavily saturated colours. Turn the colour and contrast and brightness up high. Do any of the colours "flare" out to the right.
4. How is the focus. Is it noticeably worse at the screen edges. Does it "defocus" on high brightness scenes ?

If you turn up the brightness fully is the picture bright even if it is not clear ?

Can you brighten what would be dark areas of the picture or not ? This perhaps points to other trouble if you can't.

Let us know what it does and how you get on

[terminus]

Thanks for this checklist Mooly.

To address your points:

1. Unfortunately I can't remember what the start up time was when the TV was new. Currently from start up the MD4 takes about 6 seconds for the picture to begin to appear and peak brightness occurs at approximately 20-25 seconds. The JT1 takes 3-4 seconds to begin to appear and peak brightness by 7 seconds.

2. There no obvious tint during the first few minutes. The colours seem to be balanced.

3. I put some cartoon channels on and turned everything to full. There was no flaring.

4. Focus is the same across the screen at any settings and on any scene. The picture does have a general lack of sharpness compared to the fresh and crisp JT1 or a new 32" Daewoo DUA-3291.

Turning brightness to 100% on the MD4 significantly improves the clarity of dark areas. And it causes very little white misty effect on the picture. The JT1 with 100% brightness has a very intense white mistyness, as did the DUA-3291. So at 100% brightness the MD4 is actually watchable, whereas a normal set isn't.

Brightness at 0% create a similar impaired PQ on the MD4 and JT1.

[Mooly]

Hi,
Well it could be good news. The fact you say you get a good (yes !) picture with the brightness turned right up, and that doing this doesn't make the dark areas too bright does perhaps point to internal adjustments that may be required. Is that a fair assesment would you say -- the picture is OK but lacking "brightness".
No flaring, no tinted colours, good focus are all good signs CRT wise.
The "Grumpy one" could be spot on the mark

[Grumpy Old Troll]

The "Grumpy one" is always "spot on the mark".

'Mooly' - As I said in reply to your post condemning 'terminus's' set to the scrap pile, I've seen lots of these sets over the years. And never seen a duff tube in one.

So I'll say again - Improvements could probably be made by a decent TV engineer quickly & cheaply on-site in less than 20 minutes.

[terminus]

Originally Posted by Mooly

Is that a fair assesment would you say -- the picture is OK but lacking "brightness".

Yes, the lack of brightness is the thing really. And generally focus is a bit soft. Relieved to hear these sets have reliable tubes. Thanks for the assessments.