Problem with red on a Panasonic TV.

[Nigel Goodwin]

Mr Goodwin,

Surely you jest.

NO!, I've been repairing TV's professionally for 35 years, I've seen LOAD'S of duff tubes, certainly dozens per year. The current really cheap sets (mostly made in Turkey) have a VERY short tube life, and Philips tubes are well known for early failure, no matter what set they are in. I probably see at least one Sony Trinitron duff per month - but we are a major Sony dealer!.

 

[tunedwolf]

I would say Nigel is correct here...

Modern sets, certainly all that I have seen in the last 15+ years, have all used one scheme or another for automatic tube compensation. When the tube can no longer be controlled by automatic means, all sorts of poor picture troubles show up. Probably among the most common would be flaring of one gun or another, usually seen as streaks of colour around edges in the picture, but at the same time a lack of definition of that colour in the actual picture content as a whole.
Loads of fairly modern sets will actually blank the picture completely when the tube wears beyond automatic control. Philips sets seem to be very prone to this in my experience, or maybe I have just been unlucky...also most of the sets in recent years I have ran across using Philips tubes all seem to have had tube issues of some sort or another. About 5 years ago I had two that failed within warranty, the original factory fitted tube, and the replacement sent from the factory several months later, I chased the set to another dealer the last time to fight the warranty claim.

A common trick, to get a last gasp from a dud tube a good few years back, was to reduce the filament resistor in value a little, making the cathodes a little hotter, but to be honest, the mileage of doing that in a modern set is doubtful at best. I think your best bet is to rip out the chassis and donate it to your local repairman for spares, and scrap the cabinet and tube at the local amenity tip. It's unfortunate, but we now live in a throw away world, and the cost of a repair of this nature would be better spent on a new set.

 

[penoy_balut]

if you can check voltages on cathode drives (RGB) and they are good then tube could be defective

 

[Nigel Goodwin]

Philips sets seem to be very prone to this in my experience, or maybe I have just been unlucky...also most of the sets in recent years I have ran across using Philips tubes all seem to have had tube issues of some sort or another.

As I mentioned earlier, Philips tubes have had MASSIVE reliability problems, many set manufacturers have extended the warranty on the tubes because they know it's a manufacturing defect and they don't have a leg to stand on in court!.

 

[HiTech]

The red is dim and is also permanently bloomed, turning the brightness up only makes it worse.

I take it from what you're saying that the tube is probably damaged, is this true?

Without using a CRT tester to confirm the condition of the CRT, I would now strongly suspect the problem to be the picture tube. Can you get ahold of a CRT tester or have someone test it for you? They should also be able to rejuvenate it as well. Rejuvenation does improve things for awhile... depending on how many hours daily the set is used it could last for months to a year or more to just several weeks.

 

[Hero999]

Also as it's been deteriourating for awhile. . .

Anyway, I'd like to learn more an oscilloscope has a focus control, right? so do you think the red electron gun has just become badly out of focus? Perhapps the focussing circuit has gone wrong and it can be repaired. There again it might be electron sputter on the red cathode, this would certainly explain why it's deteriorated over time, in which case the tube is probably worn out.

 

[Nigel Goodwin]

Also as it's been deteriourating for awhile. . .

Anyway, I'd like to learn more an oscilloscope has a focus control, right? so do you think the red electron gun has just become badly out of focus? Perhapps the focussing circuit has gone wrong and it can be repaired. There again it might be electron sputter on the red cathode, this would certainly explain why it's deteriorated over time, in which case the tube is probably worn out.

The focus is common to all three guns, generally what happens is one, or more, guns go 'low emission' - as suggested boosting the CRT might help short term, but modern tubes don't boost terribly well!.

 

[Hero999]

What about the blooming on the red? I take it nothing can be done about this?

 

[HiTech]

The blooming is a result of the low emission. Just install a new CRT, or test & rejuvenate it, or dump the whole thing in the trash and buy a new set, make a sandwich, sit down & relax to a good movie.

 

[Hero999]

I think we'll dump it and buy a new TV, since analogue TV is going to be turned off in a couple of years time so we'll need to go digital anyway.

 

[HiTech]

No, No hang on to it, fix it, and just buy a conversion box when digital is mandated. Afterall, I bought alot of stock shares in GI, Scientific Atlanta and others who'll be making those set-top converters!!! Please I need the investment return!

 

[Nigel Goodwin]

No, No hang on to it, fix it, and just buy a conversion box when digital is mandated. Afterall, I bought alot of stock shares in GI, Scientific Atlanta and others who'll be making those set-top converters!!! Please I need the investment return!

Not going to get much from the UK with those! don't see them over here.

 

[audioguru]

I am in Canada where they said TV will all be digital and high definition by now. It isn't. Not in the USA either.
A few people watch high definition TV on plazma or LCD screens but most people still have analog TVs with CRTs.

 

[Hero999]

No, No hang on to it, fix it, and just buy a conversion box when digital is mandated.

If I fixed (assuming it's repairable) it will only last for a couple of months at the most. I think I'll just bump it and buy a new one, now we just have to decide what new TV we want.

 

[HiTech]

CRAP
RCA/GE, Sanyo, Magnavox, Phillips, Sylvania, Funai/Symphonic


DECENT
Toshiba, Sharp, Panasonic


GOOD
Sony, Mitsubishi, JVC

 

[Nigel Goodwin]

I am in Canada where they said TV will all be digital and high definition by now. It isn't. Not in the USA either.
A few people watch high definition TV on plazma or LCD screens but most people still have analog TVs with CRTs.

The UK will have no analogue TV at all bt the end of 2012, the switch-off is going to be done in regions at a time - with the first in 2007, Whitehaven in Cumbria will be the first town to go all digital.

Currently almost all of the UK can get digital TV from satellite, quite a lot can get terrestrial digital, and a fairly small number can get digital cable.

HD is currently only available via satellite and cable, although limited tests have been done terrestrially in a small part of London, with special boxes being used. However, due to the bandwidth limitations of terrestrial transmissions it's doubtful if it will be practical?.

 

[HiTech]

In the US the FCC mandated that large viewing markets would be the first to go digital and so far most have while retaining their analog setups as well. The smaller markets will be required to switch over around 2008 but that deadline has been pushed back a number of times ever since the first deadline of 2004/05 was mandated. It's a real pain here since there's a mish-mash of wide screen, HD, analog and whatever else can be squeezed onto a screen. I wish things like this would stabilize. Just like CD/DVD formats that never boil down to one format. Then again what should I expect since videotapes still come in a variety of formats.... after years of industry efforts to narrow them down to 2 or 3 types.