Single bright horizontal line across the screen. Guessing it's the vertical deflection based on some internet research. Any possability of a service switch on this set that may be bad? Anyone happen to have a service manual for it?
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Re: Sanyo DS31590 31" TV vertical deflection
If the vertical is not defective or shorted there is a possiblity of bad solder connections on the vertical ic. If connections are good and has b+ voltage to the chip replace chip which is IC 501 LA7841 or LA7845 and change c511 (decimal point 1 film capacitor)
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Vertical scan output section circuit fault. Absence of vertical scan causes the single horizontal line on screen. Horizontal scan output section is OK. Contact any service technician to troubleshoot the vertical scan output section circuit. If you wish to get some details; check the site linked here. Pull up older posts.Surf the site with patience.http://electronicshelponline.blogspot.com/
Horizontal line fault to CRT based TVs are given.
CAUTION: To prevent damage to the CRT phosphors, immediately turn down the brightness so the line is just barely visible. If the user controls do not have enough range, you will have to locate and adjust the master brightness or screen/G2 pots.
A single horizontal line means that you have lost vertical deflection. High voltage is most likely fine since there is something on the screen.
This could be due to:
Dirty service switch contacts. There is often a small switch located inside on the main board or perhaps accessible from the back. This is used during setup to set the color background levels. (On some sets, this is located on the CRT neck board and may be a jumper plug or other means of selecting service mode - not an actual switch.)
When moved to the 'service' position, it kills vertical deflection and video to the CRT. If the switch somehow changed position or got dirty or corroded contacts, you will have this symptom. Flip the switch back and forth a couple of times. If there is some change, then replace, clean, resolder, or even bypass it as appropriate.
Bad connection to deflection yoke or other parts in vertical output circuit. Bad connections are common in TVs and monitors. Check around the pins of large components like transformers, power transistors and resistors, or connectors for hairline cracks in the solder. Reseat internal connectors. Check particularly around the connector to the deflection yoke on the CRT.
Bad vertical deflection IC or transistor. You will probably need the service manual for this and the following. However, if the vertical deflection is done with an IC, the ECG Semiconductor Master Substitution guide may have its pinout which may be enough to test it with a scope.
Other bad parts in vertical deflection circuit though there are not that many parts that would kill the deflection entirely.
Loss of power to vertical deflection circuits. Check for blown fusable resistors/fuses and bad connections.
Loss of vertical oscillator or vertical drive signals.
The most likely possibilities are in the deflection output stage or bad connections to the yoke.
There is a failure in the vertical deflection circuit. Typically there is a vertical output i.c. that provides the deflection vertically. The i.c. itself is a fairly common component to fail. There are some lower power circuits that feed this output device that also could be the problem. When the electron beam in the tube is not deflected vertically it "writes" only horizontally across the center of the screen thus resulting in a single trace. Be careful not to leave this at high brightness for any extended time as it can "burn in" that area of the screen. Unless you are a "techi" this is a job for a qualified technician. Troubleshooting would be in the vertical deflection section of the set. Most of the parts are not expensive in themselves, except for the deflection yoke which sits around the neck of the tube. The cost to repair would typically be the shop labor.
I have a similar problem on my CRT computer monitor (AcerView 76c). It is an old screen and I think it is just at the end of its life, much like your TV. Having some background in physics, I would be pretty sure that the problem is with the cathode ray tube's vertical deflection system. The horizontal deflection electrodes are working while the vertical one is not. This results in a display of a single horizontal line (or in my case, a few superimposed) in the centre of the screen. Where both X and Y (horizontal and vertical) deflectors fail then the electron gun firing would result in a single bright spot in the dead-centre of the screen.
So really, we have no choice but to move on and buy a new set as repair is probably just as, if not more, expensive than replacement with a new device. Seeing as your post was in 2007, I hope you managed to solve the problem.
yes it can still be fixed! the pop sound you've heard maybe came from a blown capacitor in the vertical deflection circuits. this symptom, sometimes called the tube light effect, it is characterised by a bright thin horizontal line across the middle of the screen. this symptom is caused by a breakdown in the vertical deflection circuit. hence maybe the trouble maybe in the vertical oscillator, amplifier or output circuits. but if all i have said is not clear to you, better bring it to a qualified tv technician. good luck!
this symptom, sometimes called the tube light effect, it is characterised by a bright thin horizontal line across the middle of the screen. this symptom is caused by a breakdown in the vertical deflection circuit. hence maybe the trouble maybe in the vertical oscillator, amplifier or output circuits. but if all i have said is not clear to you, better bring it to a qualified tv technician. good luck!