banjo said:The wire around the flyback is probably useful only for a heater to cathode short. Probably the technician has found that the short is between the control grids and does not involve the cathode directly.
Rejuvenating to remove a short works some of the time. It is worth a try. However, it should be done with the tube resting on its face. That way any dislodged particles are carried by gravity down into the bell of the tube where they cannot do any harm.
I have also been able to tap out some shorts with a plastic brush handle. This is somewhat dangerous, so do not attempt it yourself or if you do wear safety glasses and a heavy jacket. The idea is to again place the set on its face and operate it until the screen goes blue. Once the oxides are causing the short, the neck of the tube is tapped with the plastic brush handle to shake the tube elements and dislodge the particle. The danger is two fold. First, the tube is operating so lots of high voltage is present. Secondly, the tube is under high vacuum, if you tap too hard, the tube could implode and throw off glass fragments. When successfully tapped, the screen will immediately return to normal.
I would question the repairman as to what methods they tried so far. If they have already tried the above, then assuming that the warranty on the picture tube has expired, I would start looking for a new TV. Unfortunately, the replacement cost of the tube is usually more than another set.
---- Steve
banjo said:John,
If the set is only 14 months old, then there is a good chance the picture tube is still under parts warranty. I would take the set back to the repair shop and ask who to contact about the warranty on the picture tube. Tube warranties have been dropping every year, but they are still typically at least 2 years. Ask for the phone number of the manufacturer's area representative. Call this person and politely tell them that you are extremely disappointed in the performance of their product.
If the manufacturer had a bad run of tubes, they will usually replace them for the customer's that complain. Sometimes they will cover parts and labor to make the customer happy. Other times only the parts. Typically, the bench charge for replacing a tube is about 2 hours since numerous adjustments are required. You would have to pay this labor charge, but it should be much cheaper than a new set.
Make sure the repair shop understands that if they can help you get the tube under warranty, then you will pay the install labor. Otherwise, they really do not have a big incentive to help you.
The reason for taking the set back immediately is two fold: first, it not really useable to you. Secondly, when it is taking up shelf space for the repair shop and returns under their 30 day warranty period, they are more likely to give the matter a higher priority.
I contacted the technician again today and he said the problem I was having each time occurred briefly yesterday again (at least while in the repair shop again this time) so he did a test and his equipment indicated there's no short to the cathode so clearly the original repair was not the problem - right?(I am confused) and he now says it's definately not a short to the blue gun but something outside the picture tube.He replaced a couple of resistors at the bottom (whatever that means) and it's running fine but he wants to continue testing it. It seems to me it's guess work on his part and i have no tv stillI said at this rate his warranty would be running out, it's now 13 days into the arranty but he said not to worry about that as all his work is guaranteed.Not exactly sure what that means.
He also said yesterday he'd contacted the manufacturer via fax but as of y/day had not received a replyWhen I asked when i was gonna get it back he said as soon as he had a definate awnser - doesn't exactly help me much.
But now he says it's definately not related to the tube so it would seem that it doesn't need replacing even if as you suggest the manufacturer's would do the right thing by me seeings how the set is so new. I will keep you updated.At least on here there's no smart ass comments like on the google elecrics groups.
Thanks
john
ps if you need a scan of original repair warranty I can scan and attach it next time,but I sort of covered it all in my previous post. Very dissapointed by all this.
---- Steve
banjo said:John,
Given the symptoms, the problem is a DC bias issue. It could be internal to the tube or external. Externally, this signal is handled as a dc-coupled signal typically from the video output IC to the picture tube. If we assume that the video output IC is OK since the other two colors are fine, then this leaves the tube and the driver transistors and components in the blue gun circuit. The transistors can be eliminated by either replacement or substitution. The identical pairs of transistors are in the red and green circuits. If the technician swaps the transistors and the problem moves to another color, then the transistors are intermittent and the repair is straightforward.
If he is offering a 30 day warranty, that time period should start after the repair is finally complete, not from the initial request for service. However, it is up to lawyers to interpret the real legal meaning of his warranty statements.
My first question now is this repair shop authorized to do warranty repairs on this brand? Check with the manufacturer, usually they have a listing on their web site about what shops are warranty stations in your area. Perhaps he is not authorized to replace the tube under warranty and is therefore not willing to consider it the culprit. I would still contact the manufacturer about your problem, explain the symptoms and if they are having picture tube problems, they should be pretty helpful. If the current shop is not the authorized warranty repair station, call the repair shop that is authorized and get their opinion. The authorized shop will see the biggest volume of these sets. Therefore, they will know if tubes are going out. Also, authorized shops would receive any service bulletins notifying them of any field upgrades or fixes for recurring problems.
You may have to take your losses, pull the set out of this shop, and take it to another one. Changing a picture tube is a fairly big job for a TV shop. With the prices of TVs constantly dropping, the new shops probably don't change as many tubes as we used to do in the old days. (I am an engineer now, having left the TV business 15 years ago.) Perhaps he is not willing to tackle this size of job.
Regardless, call the manufacturer. If their full warranty was 1 year, then you are only just a couple of months past that. It is unreasonable that a TV less than 2 years old is unrepairable! Keep asking the manufacturer who can repair it and who else in their company you can talk to about the problem.
--- Steve
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