Which circuits warms up the tv?

It appears normally, and the picture quality is as if I purchased it new yesterday.

Here is another clue, sometimes it will startup when I press the tv button (which switches between the normal aerial channels and the sky digibix scrat connection, seems like your spike theory is gaining ground...

On Tue, 07 Nov 2006 06:01:36 -0800, z Has Frothed:

Ok so the CRT is probably ok. Have you noticed that the back of the CRT is glowing orange (filaments) while there is no picture and if so, does it glow with the same intensity as when the picture appears? If so the filament source can be ruled out. Also have you listened closely to the set when the picture appears? Is there a crackle of high voltage? Does a relay click? Degauss hum for half a second? There are so many things that an experienced tech can diagnose just using their ears, eyes, and nose. I can usually tell if a set has HV just by looking and listening to it with the back off among other things like listening for deflection scans, flyback noises, smps noises, whines, whistles, hums etc... etc... etc... Certainly a can of freeze mist would be the very last thing I would reach for.

Not many if any are going to teach you how to diagnose a tv in person let alone by posting messages in a news group. The assumption is made that you have a reasonable amount of experience in fixing what you're trying to fix and that you have exhausted any other avenues you have available locally before asking questions in a news group that is propogated globally.

If you need to ask a question like that, you probably shouldn't be messing with the potentially dangerous voltages around a CRT!

The heater is supplied by two of the pins in the connector on the end of the tube neck, and in a TV usually gets its power from an extra winding on the line O/P transformer.

Sounds like maybe the auto-greyscale balancing circuit could be playing up, alternatively some sets blank the picture if the A1 preset isn't set exactly just so!

Have you read my previous answers? I said that the crt is glowing from the very start.

Well, I am not a professional, but I gather from the faq of this ng that it is very hobbyist friendly. Having said that, the advise meeted out is probably also on a hobbyist level, so is to be taken with a pich of salt...

Its been established in the flow of posts so far that your PSU is almost certainly starting normally and the line O/P is very probably doing so as well, it seems increasingly likely that the auto-greyscale circuit is detecting an excessively worn CRT and shutting down the cathode drives. On some sets an incorrectly set first anode can also confuse the g/s circuit.

On Tue, 07 Nov 2006 07:02:25 -0800, z Has Frothed:

I didn't say it wasn't hobby friendly. Hell I started out as a hobbyist and I was just giving you an opinion based upon my 30+ years of on the bench experience (retired now) that some things are best left to qualified service personel. I have seen many hobbyists turn simple repairs into expensive ones and even worst situations where the device wasn't repairable.

Good luck

Why would it be doing that? What possible consumer benefit could be obtained by greyscale shut down as you describe? Are you seriously saying that the people at Panasonic will deliberately install a circuit that shuts down the tv. I have never heard of such a thing, they could be sued for that. Are you really sure about that???

Most modern CRT displays have a multitude of safety shutdown circuits, this can be very frustrating for the service engineer as often the unit will shut down in response to relatively minor faults, making it impossible to observe any symptoms that might betray the nature of the fault.

On the rare occasions that the service manual can be obtained at reasonable cost (if at all!) these sometimes give guidance on which safety trips can be overridden for servicing purposes, otherwise it can be a minefield - if you short the wrong safety trip the unit can fail catastrophically at switch on!!

No, the newsgroup is for electronic techs to exchange information. The group will help a beginner, but it is considered criminal to give advice, without the proper warnings. A TV can kill you, if you don't know what you are doing

On Tue, 07 Nov 2006 08:29:37 -0800, z Has Frothed:

This is starting to smack of a troll.

What are you going to sue them for? Trying to comply with international safety standards? You really are ignorant of how the electronics industry works, after the lawyers got their hands into it.

Why could they be sued for incorporating a circuit that shuts down when a fault is detected? Sounds like good common sense to me, the service literature generally explains how to narrow down which shutdown is occurring so the problem can be diagnosed.

oh, I see all the "experts" are joining in... so if as the original replyer suggested the grayscale circuit detected a bad crt than the common sense thing to do would be to make the tv stop working now rather than give the poor customer a few more month of pleasure. Sure, I believe you...

go away! you already asserted that you will not help why r u still here?

You were given sound advice by several different people, its not their fault its not what you wanted to hear and taking that attitude won't change that!

"If these were woodworking newsgroups, their questions would be the equivalent of "What are the best kind of rocks to use to pound screws into fine furniture?" When someone tells them to use large chunks of granite, they are happy, but if you try to tell them about screwdrivers, they explode into a rage."

No, it isn't. The idea is for those with experience to help those with a little less.

Would you go to alt.brain.surgery if you had a headache?