Question about Televison & Video
Without seeing the set and checking it out, this is hard to accurately tell.
The following is when a single CRT or tube in a projection TV set starts to get weak. It is the same for a CRT when any one of its electron-guns starts to go weaker than the others.
On any CRT based set either with a single CRT or with seperate projection CRT's, as the tube(s) (CRT's) get weak their emission goes down. One of the symptoms is that the beam focus gets softer.
When a CRT goes weak the beam current will decrease. This lowers the mass or intensity of the electron beam. This makes the beam width wider, and thus the image focus is softer. Having a wider beam in a single CRT or single colour section of a CRT's electron gun also means that there will be more beam width overlap in comparison to the other CRT's or the other electron-guns in the case of a single CRT. This will give the appearance of an overlap or edging especialy with sharp or thin lines.
There is also a symptom where the convergence can get less accurate as the convergence control circuits age. This means that the scan tracking between each of the CRT's or the electron-guns in a single CRT start to not be able to accurately keep converged to each other. This will produce a border effect between the beam position accross the scanning of the screen.
Sometimes with a projection CRT set if there are separate focus controls in the high voltage (HV) section for each of the colours the beam focus may be able to be cheated if the CRT is not too weak. In most CRT sets the focus voltage is shared between all the colour channels, and thus there is no possiblity to control each channel individualy.
With weak CRT's there are other factors that come in to effect. One big one is that the colour tracking gets impossible to be accurate. This is because the gain liniarity of the tube becomes out of spec. As each of the CRT's or the electron-guns in a single tube become weak they will lose their tracking accuracy in relation to each other. In the design of the drive circuits of the better TV sets there are some auto circuits to try to make sure that the tracking is stable. But, when the electron-guns become too weak the circuits run out of range.
Posted on Apr 14, 2008
A 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
The service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Jan 27, 2013 | Hitachi 43FWX20B 43" Rear Projection...
May 04, 2009 | Televison & Video
Feb 10, 2008 | Philips Magnavox 51MP392H Rear Projection...
473 people viewed this question
Usually answered in minutes!