Tip & How-To about Televison & Video

Kitchen table, Screen (G2) voltage adjustment, Course 101

Well, those of you who have no idea why a Screen Voltage (technically known as G2) adjustment may interest you, here is a photo of a bad adjustment (too high).



You may also experience smeared colors… this is caused by a low adjustment. To correct this, we need to get the back off of the TV. It would be a good time to unplug it if you have not already done so. Next we locate the FBT (Fly-Back Transformer).



This is a 20” model and it has 2 knobs. Your FBT may vary, as some slim designs and some large tube models may have 3 knobs.

You will need to look closely at the knobs; they will be labeled “Focus” or “Screen”. On units with 3 knobs, there will be 2 focus knobs and 1 screen. For now, we will be working with at the Screen knob only.



With the adjustments identified, we are ready to plug the TV in (including your standard cable connection) and turn it on… BECARFUL!!! For the rest of this adjustment, we will be working inside of an electrically charged TV. We also need to normalize the picture, so go into your TV menu and adjust the Picture and Brightness settings to the middle or center.

If your TV normally displays a black screen when you do not have a signal connected, ex: Video input 1, then this will be the quickest and easiest setup for you to use. However, if you are not so lucky, you may need to bust through your DVD video collection and find a “between scenes” shot that you can pause on to give you as black of a picture as possible. Eliminate as much light in the room as you can (just remember, you still need to see what your doing)… we want a good view of the screen without the interference of ambient lighting.

Once you have your black screen all set, we are now ready to proceed to the adjustment. If you have lines on the screen, see (HIGH)… if you have color smear, see (LOW).

HIGH: If you have some lines in the picture with a washed out appearance, your Screen voltage is too high. You will need to turn the Screen knob on the FBT counter-clockwise. Do this slowly, until the lines are no longer visible. If you still have a small amount of illumination coming from the screen, back it down a touch further until this just disappears.

LOW: If you have smeared colors in the picture that seem to trail of the edges, your Screen voltage is too low. You will need to turn the Screen knob on the FBT clockwise. Do this slowly, until you just see some lines zigzagging top to bottom on the screen. Now, you will need to turn the Screen knob on the FBT counter-clockwise. Do this slowly, until the lines are no longer visible. If you still have a small amount of illumination coming from the screen, back it down a touch further until this just disappears.

The final set, switch the TV input over to your cable input and check out the picture. Take a good look at some bright scenes and dark scenes. Do they look ok? Adjust the Picture and Brightness in your menu… can you set the picture to your liking? If so, you are all set. If not, double check your work (remember to normalize the Picture and Brightness setting).



If you are unable to adjust the Screen voltage as described above, you may have a High Voltage problem with your TV. This will require a repair and is not covered by this tutorial.

If you are all set and the adjustment is good, we should have a quick look at the focus adjustment. Return the TV to your Black screen setup. Press the TV menu button to give you nice fixed display to focus. Adjust the focus knob(s) until you have the clearest picture. It’s important to balance the center of the picture with the corners of the picture. If the center is too sharp and the edges and corners are blurry, it is not a good adjustment. Do your best, you are the final judge of your work here.



Once you have finished the adjustments and verified the picture with your cable picture, you are ready to close it up and return the TV to normal service. Unplug the TV, replace the back cover… enjoy!

I hope this was helpful. If you benefit from this tutorial, please leave some feedback.

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1 Answer

Why or what causes the TV to have white lines acros the screen ?


This is caused by too high g2 voltage on the picture tube. Most likely the voltage divider (built in the flybakc trafo) has drifted . Or, someone turned up the voltage, using the adjustment potmeter located on the flyback trafo. In general there are two adjusters. The top one adjusts the focus, the bottom one adjusts the g2 voltage. Try to turn this on a bit lower, until the white lines disappear. This voltage determines (also) the cutoff point from the CRT. If it does not help, then there might be a problem with the horizontal or vertical blanking signal. This is not so easy to cure. You need the schematic, oscilloscope and technical understanding of how it should work.

Oct 19, 2014 | Televison & Video

1 Answer

How and where can i locate the g2 high voltage to the blue tube on a 65" mitstubishi HDTV model WS-65511 serial :118393 so i can adjust it ????


g2 is also known as screen voltage. the adjustmen knobs are located on the high voltage block behind the front panel. its a black square bloc with 6 adjustment knobs ussally label focus and kscreen one for each and one for each tube. WARNING ADJUSTMENT OF THESE can be tricky and inpoperly set will cause shutdown of set.

Oct 16, 2010 | Mitsubishi WS-65511 65" Rear Projection...

1 Answer

my screen have some red lines


I will assume from you description that this is a rear projection crt(picture tube) tv. if this is true I have good news/bad news.
faint red horizontal bowed lines in the picture indicate the screen(G2) voltage for the red tube is too high.Slight lowering of the G2 adjustment will eliminate these lines. I stress SLIGHT because too much adjustment will mess up the gray scale .
The bad news the red crt made be bad. if the adjustment works but in the future the problem reappears then suspect the red crt.red crt replacement is probably not economical to repair.

Jun 09, 2008 | Mitsubishi WD-52525 52" Rear Projection...

1 Answer

light blinks wont start up


5 flashes is current to cathode detection (IK). this can be caused by a bad focus block, bad driver ICs on the CRT board or the CRTs them selves. I would start with the focus block they have been known to go bad (leak voltage). have a tech replace them because G2 is a critcal adjustment.

Feb 20, 2008 | Televison & Video

3 Answers

brighteness


In my case, the adjustment was available from outside the TV. Sortof. On the rear of the TVabout 2 inches to the right of the coax in, there are two vertical slits on a little protrusion. Inside the slits are the two adjustment screws. The lower screw adjusts brightness, the upper screw adjusts focus. I spend 30 minutes popping the case apart just to find that I could not access the adjustment screws from inside. Lo and behold, they made them easily accessible from the outside. On a side note, I have never seen a TV designed as poorly as this on the inside. You have to literally reach in and unplug things just to get the back off. All the electronics save the tube itself are mounted to the rear chassis. On all other TV's I've seen (taken apart, rather), all the electronics are in the FRONT part of the chassis so that they move WITH the tube.

Sep 23, 2006 | JVC AV-27530 27" TV

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