Forum Home
Press F1
Thread ID: 15228	2002-02-01 05:05:00	Monitor blues (and greens and browns)	Guest (0)	Press F1

Post ID	Timestamp	Content	User
33882	2002-02-01 05:05:00	I'm presently using a PC Company 17' monitor (about 3 yrs old). About once a week, when turned on from cold, the screen looks like something from a sixties hippy commune. There are green blobs in both top corners and brown blobs down both sides with a general grey along the task bar and a deep purple background. While this looks cool, it is rather impractical. A de-gauss burst cures it, but can anyone tell me what causes it? There are no apparent strong magnetic radiators close by (the 34' tv is about 1.5 metres away and a hifi speaker is about half a metre above the monitor, but neither of these have been turned on today and the monitor has gone psychadelic since this morning). I don't think the monitor has access to pot or acid so what's it on man? Will it cause long term damage to the monitor, or is it too late?	Guest (0)
33883	2002-02-01 05:26:00	Hi Ray It may be the way the purity in the tube was set up. It may have been set up 'North/South' and now the monitor is sitting 'East/West'. Try moving it around 90 degrees and see if it makes any difference. Although this would be strange after 3 years, unless you rotated your house lately? You mention that this happens when the monitor is turned on when cold. Do you mean from stand-by (a light shows on the monitor when it's off)? If so, you may find that turning it off completely using its own on/off switch will solve the problem. Failing that - you must have introduced some other magnetic field into an area close to your monitor. Try rotating the speaker that is half a metre away, and see whether the hippy coloured patterns move as well. Good Luck J.	Guest (0)
33884	2002-02-01 05:33:00	Are you on drugs?	Guest (0)
33885	2002-02-01 05:38:00	Thanks Jester for the rapid response. Further explanation - the monitor is about 3 yrs old but I've only had it for a couple of months (its on loan from a friend as mine died). Are you serious about this east-west thing? I knew monitors were manufatured for different hemispheres, but direction as well? or is this something that happens due to the Earths magnetic field when they are aligned one way for a long period. If so, how will I fix it? I'll try turning it round 90 degrees but I'm gonna look a tad stupid (stupider?) sitting at the end of my desk! And yes, I meant from cold. The monitor has an ON switch, but no OFF switch but I have a master switch that turns the power of to all devices when I'm not using the puter.	Guest (0)
33886	2002-02-01 05:46:00	No need for drugs, D.A.R.E. - I'm addicted to Press F1!! (are you related to the famous Dan Dare?). I do alcohol now and then, but only to keep sane.	Guest (0)
33887	2002-02-01 07:52:00	Hi Ray You can forget the hemispheres, turning upside down or changing the points of the compass. All that those will do is introduce further purity errors that will confuse the issue. Likewise you can forget about turning through 90 degrees because this is not really going to tell you anything. Similarly the speakers will not be the cause if they have not been moved closer, and even then, the problem would statically induced and would not just appear occasionally when switched on. I agree with Jester that manufacturers align their CRTs in an E-W direction and that is to ensure that no matter how you orient the monitor in use, the effective polarity of the earth's magnetic field cannot change through more than 90 degrees (when the monitor is used in the hemisphere it was designed for). If it was aligned N-S you could induce a 180 degree change. (I too was involved in TV repairs in a previous life.) The problem is most likely due to a failure of the auto-degauss circuits, especially since switching on from cold introduces the problem (if I read your post correctly) What is probably happening is that the auto degauss is malfunctioning and actually gaussing your screen, an effect that the manual degauss is able to correct. If you didn't turn the monitor off, it would probably stay pure. There is no easy solution to this problem other than to have it serviced. This should not be expensive but I would have it done by a TV repair shop that also does monitors as they are more likely to understand the problem and won't need to ship it off to a monitor specialist. I don't quite understand what you mean by it having an on switch but no off switch though. It should toggle on and off with the same switch, however if there is a problem with the switch action it could be linked to your auto-degauss issues. Here are two simple tests you can carry out to confirm whether or not the auto-degauss is even trying to operate: Let the monitor cool down for 30 minutes or so then get your ear close to the screen and switch on. You should hear a fairly loud 'thoonng' noise as the degauss current peaks rapidly then dies off exponentially. (This causes a magnetic pulse which mechanically excites the steel shadowmask inside the tube as it degausses it and that's what makes the noise.) If you hear nothing, try the manual degauss which should produce a similar sound. If the first test fails but the second works then you definitely need to take it for service if you want it fixed, or just keep up the manual degauss which is much cheaper! Of course, it could be a simple as a loose plug to the degauss circuit. The current levels are high and a loose plug will arc a little each time the set is turned on and will eventually develop a high resistance connection. This wiill inhibit the degauss current and cause gaussing! If you are feeling brave enough, unplug the monitor, take the back off and have a look for a two or three wire bundle coming down from the region of the front of the screen and going to a plug somewhere near to where the mains cord goes into the back of the monitor. Cheers Billy 8-{)	Guest (0)
33888	2002-02-01 21:41:00	Thanx again to all for the replies. Extemely interesting stuff. The switch on the monitor definitely only turns it on. Once it is on you can push the said switch all you like - it has no further effect - strange eh! I can hear the noise that you refer to at switch-on, Billy, so I guess that bit works. This morning, I asked the guy who lent me the monitor if he knew of the problem and he said _ 'Well Duh!! That's why I bought a new one and gave that one to you!' so I guess as long as it works I'll continue to use it as it is (I'm saving for a new 19' monitor at the moment). I'm not allowed to take the back off tvs or monitors. I did this a few years ago to a 21 month old telly we had, to see if i could stop the high pitch whistle it gave out. (percussion maintenance to the top of the said telly worked but I wanted a more permanent fix). So i took the back off, found the offending loose heatsink, applied some Elephant Snot (silicon sealant) and put the back on again. I failed to notice that I had trapped the HT lead when doing this, so the next day my daughter says 'Dad, the TVs on fire', and it was! Burnt out the line-output tranny and blew the picture tube. Consequently, 'she who must be obeyed' has a large hissy-fit if she sees me taking the back off a monitor or telly! That's also why I like to turn everything off when I'm not using it. And no, D.A.R.E., I wasn't on drugs at the time - I don't do that now - it's so sixties, you know?	Guest (0)
33889	2002-02-04 07:44:00	Purity problems [magnetic effects on monitor or TV] If it sometimes happens, sometimes not, it is unlikly to be speakers or lack of degaussing, unless [say] speakers are placed very near to monitor. Most likely causes are: 1. Mains spikes/brownouts or 2. dry soldered joints or similar in the degauss circuit, or a faulty degauss p.t.c. If you are game enough to go inside, email me for further info Ray [another one]	Guest (0)
33890	2002-02-05 03:28:00	I've got one of the PC Co 17' monitors too. It seems to be very sensitive to magnetic fields and if the speakers for my sound card are moved a bit (they live one on each side of the monitor) they can cause colour purity problems as described by Ray. The automatic degaussing circuit only works if the power has been turned completely off (ie not from standby). Sometimes it takes a 2nd manual degauss to completely restore the colours to normal. The power on/off switch is a soft switch - press and hold it for a few seconds to turn the monitor off.	Guest (0)
1