Re: bent neck CRT pins...
+1
Loss of focus and/or darker screen image.
The more air you have inside the tube, the more the electrons traveling in the tube will collide with air molecules. When they collide with the air molecules, they will tend to scatter and not hit the intended spot on the screen that they were fired at. Also, some electronics will scatter to such an extent that they never reach the tube phosphor screen in the front - hence the darker screen image.
Yes, that is one way to spot a tube that has lost vacuum. One of my Sony GDM-FW900 is like that. Luckily, Sony designed it properly with all kinds of safety circuits, so nothing will blow even if the HV supply (anode, and G1 focus 1 and 2) is shorted out.
Actually, if anything, the heater will not light up at all if the tube has lost vacuum. It's the same with incandescent light bulbs (and why you see them blow sometimes if the bulb has lost too much vacuum). The vacuum allows the heating element to become very hot and glow, since there are no molecules inside the tube to carry away that energy. When the tube looses vacuum, now you have air molecules inside that basically cool down the heater, so it won't be able to run as hot (and thus not glow).
An easier way to think of this is a heating element running in free air and the same heating element running in a tub of water, both with same power applied. Obviously, the element running in free air will reach much higher temperatures than the one in the water.
So a good way to test a tube is to apply proper voltage to the heater pins and see if you get a nice yellow-orange glow. If you don't, tube likely has gone to air or heater has went O/C.
Is 6V what the heater is supposed to run on for your set? Check with the service manual (if you have one). Also, while you are applying a voltage on the heater pins, check the current draw as well. If the heater is drawing normal or higher current with the rated voltage but NOT glowing, the tube likely has lost vacuum.
Originally posted by Sparkey55
View Post
Originally posted by eccerr0r
View Post
The more air you have inside the tube, the more the electrons traveling in the tube will collide with air molecules. When they collide with the air molecules, they will tend to scatter and not hit the intended spot on the screen that they were fired at. Also, some electronics will scatter to such an extent that they never reach the tube phosphor screen in the front - hence the darker screen image.
Originally posted by stj
View Post
Originally posted by stj
View Post
An easier way to think of this is a heating element running in free air and the same heating element running in a tub of water, both with same power applied. Obviously, the element running in free air will reach much higher temperatures than the one in the water.
So a good way to test a tube is to apply proper voltage to the heater pins and see if you get a nice yellow-orange glow. If you don't, tube likely has gone to air or heater has went O/C.
Originally posted by eccerr0r
Comment