FAQ #56 - How do I adjust the focus on my monitor?

Originally written by Billy T

If you decide that your monitor focus might need adjustment, provided you are reasonably handy with a screwdriver and can follow straightforward instructions you can adjust it yourself. However before you leap into it, there are a couple of simple tests that you need to do first to make sure you are not wasting your time blowing up the proverbial dead horse.

Firstly, your monitor screen may be low emission and this will definitely cause poor focus. After it has been on for about half an hour it should be as good as it is going to get, so then set up a WP screen with a block of alternate lines of capital H's in both bold and normal 16 or 18 point text. Save this file with a suitable name so that you can use it again later if required.

Tip: If the monitor hasn't been used for some time (several months) leave it running for 24 hours to allow gases inside the tube to be reabsorbed. The picture quality won't be optimum until this has been done, but after 24 hours it is usually as good as it's going to get.

1) Optimise the contrast and brightness to get the picture as good as you can.

Billy's Set Up Tip:

Firstly, brightness is not brightness at all, it is actually 'black level, so the correct way to set brightness and contrast is as follows:

In subdued light, set the contrast to minimum and adjust the brightness control until the 'black' border of the screen outside the image area is just black i.e not showing scanning lines.

Now turn up the contrast to achieve the picture that you want. On old monitors it may be necessary to broggle the brightness a little to optimise the result but for most monitors in reasonable condition this should produce the right result.

2) Carefully note the image quality and any tinting of the white background, then turn off your monitor, count to 10 and switch it back on. Watch closely as the image comes back up and see if there is any pronounced tinting, whether the text is blurry, or if either effect takes more than 10-15 seconds to clear. If you find that the image is tinted (usually purple for some obscure reason) then it's a good bet that the tube in the monitor is on the way out. Similarly, if the text is blurry and does not improve significantly over several minutes, that too indicates a monitor that is on its last legs.

Tip: Don't look for perfect focus in these tests because some deterioration must be present otherwise you wouldn't be thinking about adjusting it.

Another Tip: These tests are best done in the evening without too much ambient light.

Now, if your monitor fails these two tests there is little point in trying to adjust the focus so just kiss the old girl goodbye and go get a younger model.

If it passes these tests, you can try setting the focus, but first of all, be warned that there are high voltages inside and you could get bitten. For safety's sake use an isolating transformer or an RCD if possible.

3) Disconnect the power from the monitor and place it face down on something soft and flat, not the cat or the wife's chest either. A folded towel is good. There should be about 4 to 6 screws holding the back on, so undo all of these and very carefully lift off the back.

4) With the monitor still switched off, look for a thickish (5mm) wire going up to the back of the screen. This will usually be red, black or grey, and should end in a large round cap thingy stuck on the glass. The other end of this wire will end at a large red, black or grey lump which is the high voltage transformer.

From a sub-assembly at the rear of this transformer another thinner wire (3mm) will go up the circuit board stuck on the end of the neck of the tube. You may have to remove a few bits of metal shielding to get access to the parts you want, it all depends on how well shielded the internals are.

5) Track this wire back to the transformer and you should see it enter a tallish black sub-assembly with two short shafts sticking up towards you. One of these should be labelled Focus (this may be quite difficult to see as the word is often embossed into the plastic). Don't touch the other shaft, it will not help you. If you can't tell which is which, try the top one first but note exactly where it is set as you may need to return it to its original position. They should both have a small screwdriver slot in the end.

Found them? Good.

6) Now stand the monitor up again carefully so that you are able to see the screen. It may be a bit floppy without the back so prop it up carefully, trying not to put pressure on the main circuit board. (It is ok to prop it up on its side if that is more secure but the colour may go funny while it is like that. Don't worry, it will return to normal when upright again. You can manually degauss if it bothers you.)

7) Switch on again and display the test screen I mentioned earlier. Allow the monitor to warm up for 15-20 minutes then carefully and slowly adjust the focus a little each side of the existing setting. (Should the shaft not want to turn, it may be secured in position by glue or paint. Gripping the shaft with long-nose pliers and gently exerting rotating force will usually crack the seal and Bob's your Uncle!)

If the image goes lighter and darker or changes colour as you adjust the control, you have the wrong one, so set it back where it was and try the other.

Another Billy Tip: A mirror can be really useful to help you see the front while working at the rear.

Billy's Safety Note: Put your free hand in your pocket while making these adjustments so that you don't accidentally touch live metal.

8) Once you have the right control, adjusting it one way then the other will make the image blurrier then sharper (or vice versa). Set it for the best compromise between centre and edges of the screen image, change to your desktop and touch up on the icons, again compromising between the screen centre and edges. If you are doing this in subdued light as recommended, increase the contrast just a little and make sure the focus is still ok. If not, readjust until you are happy with the result.

9) Switch off, unplug, and reassemble. If you are handy with a drill, you may like to make a small access hole on the rear of the cabinet to allow further adjustment later if required. Some older monitors have a hole there already but after the manufacturers discovered that most computer techs didn't know what focus was, they gave up providing access.

That's the best you can do for the old girl and if not happy with the results, move to Plan 2 and use as a paper weight.

Original FAQ available from here.