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What would cause horizontal lines to appear on CRTs?

post #1 of 16
8/28/07 at 8:41am
Thread Starter 
Shortly after there was some sort of electrical failure on a circuit in my house, about 8 horizontal lines appeared on my computer monitor and TV, both of which are CRTs. They span the entire width of the screen, but are very thin. Still, it's easily noticable, and it's distracting. When I adjust the angle of my computer monitor, it temporarily makes the lines disappear, but I haven't been able to do that with my TV. What could have caused this to happen? Is something like this usually caused by a damaged power supply? The TV, computer monitor, and fan are all on the same circuit, which leads me to think it's probably some sort of electrical problem... but, I also noticed the lines shortly after the power to my entire house was repeatedly turned on and off via the circuit breaker while the CRTs were still powered on (I didn't do that btw >_>)... if you have any ideas of what the problem is/how it could be fixed, please tell me. I recently bought an HDTV and I really want to move it into that room, but I'm too worried that something like this will happen again.
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post #2 of 16
8/30/07 at 11:23pm
Quote:
Originally Posted by bigmakstudios View Post

Shortly after there was some sort of electrical failure on a circuit in my house, about 8 horizontal lines appeared on my computer monitor and TV, both of which are CRTs. They span the entire width of the screen, but are very thin. Still, it's easily noticable, and it's distracting. When I adjust the angle of my computer monitor, it temporarily makes the lines disappear, but I haven't been able to do that with my TV. What could have caused this to happen? Is something like this usually caused by a damaged power supply? The TV, computer monitor, and fan are all on the same circuit, which leads me to think it's probably some sort of electrical problem... but, I also noticed the lines shortly after the power to my entire house was repeatedly turned on and off via the circuit breaker while the CRTs were still powered on (I didn't do that btw >_>)... if you have any ideas of what the problem is/how it could be fixed, please tell me. I recently bought an HDTV and I really want to move it into that room, but I'm too worried that something like this will happen again.

I will suggest getting a good A/V surge protector to reduce the risk of damage to future equipment.

hyghwayman
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post #3 of 16
9/23/07 at 4:47pm
Thread Starter 
Well, my TV was connected to a surge protector at the time, but its protection ability might not have been functional (I thought I read somewhere that they stop working after around 2 years of use... and I definitely exceeded that). But the problem is, I don't know if it's safe to plug in my new TV now. Could this possibly be a long-running incident that would affect all appliances plugged into that circuit? If it could be, would the surge protector be sufficient protection? If not, what could I do to get help with remedying this problem?
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post #4 of 16
9/24/07 at 10:06am
Bypass the surge protector and what happens.
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post #5 of 16
9/24/07 at 6:31pm
Thread Starter 
^ I just tried that right now. No change.
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post #6 of 16
9/24/07 at 7:24pm
Or you could try my soon-to-be-patented solution of leaving the devices unplugged overnight. This might work, and it's free.
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post #7 of 16
9/25/07 at 1:09pm
CableTV? Disconnect the cable feed to each device and see what happens.
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post #8 of 16
9/25/07 at 7:00pm
Thread Starter 
Quote:


CableTV? Disconnect the cable feed to each device and see what happens.

Well, yes, I am using it for cable, but the lines also appear on non-cable sources.
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post #9 of 16
9/25/07 at 7:26pm
Quote:
Originally Posted by bigmakstudios View Post

Well, yes, I am using it for cable, but the lines also appear on non-cable sources.

If you try unplugging the devices overnight, make sure you also disconnect anything that might be feeding the device any type of static or electrical interference, such as coaxial cables, audio inputs and outputs, component and HDMI cables, or anything else attached to the device.
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post #10 of 16
9/26/07 at 4:02am
Try unplugging anyway and see if it stops. Many times the cable feed/box has been known to cause a 'ground loop' which will interface with non-cable sources too.
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post #11 of 16
9/26/07 at 4:20pm
Thread Starter 
ok, I just tried unplugging the coaxial cable, and it didn't do anything. The TV must be permanently damaged, right? In my eyes, the only question is:
What caused it to happen? Do you think it was an isolated incident, or will any TVs plugged into the circuit be damaged? I'm thinking about plugging in a tiny, ancient TV just to see if it's damaged...
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post #12 of 16
9/29/07 at 12:29pm
Thread Starter 
any more help would be greatly appreciated.
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post #13 of 16
10/1/07 at 8:44pm
im signing on for some answers if you dont mind, my TV has been acting similar as of today.. here is a video of whats happening:

http://www.youtube.com/watch?v=K9QzQ_9B0i4

sounds like it could have been a similar problem?
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post #14 of 16
10/3/07 at 6:28pm
Thread Starter 
I don't think our problems are similar. My TV has thin white lines spanning the screen's entire width from the top of the screen to about 1/4 of the screen's height down from the top.
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post #15 of 16
10/4/07 at 1:47am
Are we talking horizontal lines that are slightly diagonal that run down the entire screen? If so, these are called retrace lines and are supposed to be blanked by the video IC. This is usually caused by either one of three things, first, it could be a heater-to-cathode short, but since they are white I would say it is probably not because shorts are rare and occur usually only on one or maybe two heaters (electron emitters), it would take all three to create white retrace lines). Second would be that the grid voltage is two high on the CRT (otherwise known as the G2 voltage). The third possibility would be that your RGB cutoff voltages are way too high (somehow they were reset), or a resistor or some current limiting component failed on the CRT neck board creating a larger than normal voltage to present across the filaments.

I think the most likely cause is a failure of either the EEPROM that controls your RGB cutoff voltage or G2 or "Screen" voltage to rise way too high, or a failure of a component on the CRT neck board that either allows the G2 voltage to rise considerably or the component that blanks the screen during retrace on the video IC has failed. My guess would be that has more to do with whatever EEPROM or static-dynamic memory that is inside the monitor and TV (which controls many of these voltages, on newer TV's and monitors) has either been partially corrupted, or reset to some sort of standard value that is causing you to see the retrace lines. Then again this would all be a moot point of they are not retrace lines at all. Anyway, good luck with fixing this, seriously, it can be quite tricky and expensive to diagnose and fix CRT's problems these days.
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post #16 of 16
10/18/07 at 7:42pm
Thread Starter 
Quote:


Are we talking horizontal lines that are slightly diagonal that run down the entire screen? If so, these are called retrace lines and are supposed to be blanked by the video IC. This is usually caused by either one of three things, first, it could be a heater-to-cathode short, but since they are white I would say it is probably not because shorts are rare and occur usually only on one or maybe two heaters (electron emitters), it would take all three to create white retrace lines). Second would be that the grid voltage is two high on the CRT (otherwise known as the G2 voltage). The third possibility would be that your RGB cutoff voltages are way too high (somehow they were reset), or a resistor or some current limiting component failed on the CRT neck board creating a larger than normal voltage to present across the filaments.

I think the most likely cause is a failure of either the EEPROM that controls your RGB cutoff voltage or G2 or "Screen" voltage to rise way too high, or a failure of a component on the CRT neck board that either allows the G2 voltage to rise considerably or the component that blanks the screen during retrace on the video IC has failed. My guess would be that has more to do with whatever EEPROM or static-dynamic memory that is inside the monitor and TV (which controls many of these voltages, on newer TV's and monitors) has either been partially corrupted, or reset to some sort of standard value that is causing you to see the retrace lines. Then again this would all be a moot point of they are not retrace lines at all. Anyway, good luck with fixing this, seriously, it can be quite tricky and expensive to diagnose and fix CRT's problems these days.

I only skimmed through your post right now (I don't really have time to try to figure out everything you said right now, but I will try tomorrow... I don't really know much TV... uh... jargon though >_>), and I could tell you right now that the lines don't seem slightly diagonal, atleast not to the naked eye. They look completely perpendicular to the vertical lines of resolution. I should also add that what I really want to know most is if it would be safe to put my new TV on that circuit. Barring some sort of divine intervention, we won't be getting this older TV fixed... now that we've bought a replacement for it, it's not worth paying probably a few hundred dollars for a repair. Do you think that something like this is likely to happen again, or is this sort of thing usually an isolated incident? Would a basic surge protector ensure the TV's safety? The damaged TV has always been lead through a surge protector, but I'm not sure if it was even functional when the TV was actually damaged (I thought I read something about surge protectors becoming defunct after roughly 2 years... I could be making this up >_>).
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