Refurbishing an old monitor
I have rehabilitated a quite a few computer monitors and old TV sets over the years, and am writing this node on a nicely working IBM G72 I got used 3 years ago and was on a powered display at a hamfest. I have also plucked monitors out of basements, truckload lots, saved from the dumpsters, and have done repairs to monitors on equipment I am responsible for at work. Work done to refurbish a monitor falls into basically only 4 categories today, since new CRT monitors can be purchased in 2003 for less than $100 USD for a 17 inch model.
Before putting any serious amount of effort into refurbishing a newly acquired monitor, it should first be subjected to a smoke test to determine if the monitor is worth fooling with. This involves plugging it into a computer which is set to a conservative resolution and refresh rate, and powering it up for a few minutes to test its basic functionality. If the monitor has a selectable voltage option, make sure the voltage is properly set before plugging it in! If the monitor emits smoke or strong odors of burning plastic, then it is probably a goner. Loud high-pitched squeals are also another bad sign. The monitor should at least have a recognizable display, even though it might be flakey, colors distorted, or out of focus. If it seems to lack a display, try fiddling with the video cable or smack it a couple of times with moderate force to see if anything happens. See the troubleshooting section for more information.
General Cleanup involves removing the bits of tape, spilled coffee, post it notes and general grime that accumulates on the case. If the base is cracked or a knob is missing, and there is another one available from a broken monitor, then this is also included. Another item that can be included in general cleanup is to take the back off, and vacuum or blow out accumulated dust with compressed air.
The next type of work is performed on a monitor which although it is functional, is fuzzy, dim, or the colors are not quite right. This is due to degradation of the electron guns and phosphors in the CRT. This is something that happens to all CRT based monitors and TV sets as they age, and can be compensated for somewhat by adjusting the controls inside the back of the monitor.
Beware: If you decide to take on this step yourself, be informed that there are dangerously high voltages inside all CRT based monitors, that can give you a nasty shock, and under the right conditions even kill if you are not careful!!
If the preceeding dire warning hasn't scared you off, then here is how to restore a little sparkle back into a functional, but tired monitor. To make adjustments, it will be necessary to have the back removed, and a screen displayed. The E2 Jukka Theme makes a good diagnostic display. It has a neutral background and lots of text, which helps to make good focus adjustments.
There are several groups of controls inside most monitors. The ones of most interest are Focus, HV Adjust, and Drive and Screen controls for each color. By making careful adjustments to these controls, it is possible to restore decent performance to a tired, well used monitor. There may also be controls for height, vertical linearity, and width as well. Be aware that many of these controls interact with others, so be patient and methodical. Some of these controls may be accessed via an onscreen menu on newer monitors. Here are what the various controls do, and some of the interations they have with other controls:
Pretty self explanatory. Focus does interact with Drive and HV adjust.
High Voltage can be tweaked on many monitors to minimize "blooming", which is a noticeable change in the size of the screen and loss of focus when the brightness is increased or decreased.
The Drive control determines how hard the guns are driven inside the CRT. There is usually a sort of master drive control near the focus, and individual controls to adjust the color balance. If the screen is greenish, the red and blue can be increased to compensate, or the green decreased. It is best to set the user brightness at maxiumum before making any adjustments, as it is possible to overdrive the guns and cause other problems. Too much drive will result in a washed out look.
Screen controls, like the Drive controls, help determine brightness and color balance. The screen controls adjust how the dark areas will look. Find a webpage with a true black background, and adjust for a neutral shade. Be aware that these controls will interact with your drive controls, so you may have to do a little back and forth adjustment with your drive controls for best results.
Once you are satisfied with the results, go ahead and put it all back together and enjoy! Don't expect perfection from a monitor that has been on 24/7 for several years, but you should be able to improve on what was there, and extend the useful life of the monitor for a while.
If your monitor is plauged with a certain flakiness, then it will be up to you to at least try to find the cause, which is the last type of work. A complete course in electronics troubleshooting is beyond the scope of this node, but many intermittent problems can be repaired with a little patience and a hot soldering iron. Many intermittent problems are caused by cold solder joints. One way to determine where the problem might be is to look for signs of heat on the circuit boards, particularly around large resistors and transistors. Small components rarely make enough heat to cause trouble, but the high wattage resistors, diodes, and power transistors will cause often cause problems. Your eyes and a sharp insulated probe are your best tools for finding cold solder joints. Probe suspect areas until you find an area that like an unhealed wound causes problems or temporarily fixes a problem when touched. Unplug the monitor and touch up all the soldered connections in the area with a hot soldering iron. If you are lucky you will have saved the monitor from the scrap heap for at least a while.
When to give up:
If your troubleshooting skillz haven't so far helped, then it might be time to give up on the monitor. Good used monitors and even new ones are cheap enough these days that it really isn't worth investing more than an hour or two and a few bucks on parts to make an old one work.
Here are a few signs that your monitor is better left in the dumpster:
If it smells moldy
, moisture will likely have attacked various components and connectors. If it comes on, see what happens, you might get lucky. Have a fire extinguisher handy though. If it smells burned, forget it
, there is a short circuit
or some component that has zorched
. If you are lucky it might be a tantalum capacitor
that might be replaceable if you are game enough, but a burned smell is usually a bad omen
If the brightness and color balance cannot be brought back to a reasonable level without causing details to be washed out after doing a basic focus and drive adjustment, then there is a good chance the CRT is shot
. Since the CRT costs more than the rest of the electronics combined, you might as well toss the whole thing. Even if you try to buy a new CRT, it will likely be unavailable
, or will be priced higher than a new comparable monitor. Also, any problem with the horizontal or vertical synchonization that do not yield to redoing cold solder joints is pretty much grounds for termination
. It may be possible for a qualified tech
to repair, but most minimum repair charges are close to what a brand new unit will cost. If you have several identical monitors and storage space, you might keep it for parts.
If the monitor makes a loud, high pitched whine, or you hear arcing: This means the high voltage power supply is a goner, another expensive and difficult to obtain and replace part.